Q 1:
An 18-month-old girl has been having an intermittent nonproductive cough for the past 6 months. Her parents state that the cough wakes the toddler at night a few times a month and occurs when playing
vigorously. During a recent upper respiratory tract illness, her cough worsened and occurred daily for 3 weeks. On physical examination, there is no nasal discharge, and the toddler appears healthy.
Of the following, the MOST likely diagnosis is
A. allergic rhinitis
B. asthma
C. atypical pneumonia
D. gastroesophageal reflux
E. sinusitis
The Answer :
B
Explanation :
The presentation of a chronic cough that is exacerbated during the night, with activity, and during an upper
respiratory tract infection, as reported for the girl in the vignette, most likely represents asthma.
Allergic rhinitis and sinusitis may cause cough due to postnasal drip. Allergic rhinitis typically occurs in children older than 3 years of age and is associated with other ocular and nasal symptoms, such as pruritus, sneezing, and rhinorrhea. The absence of rhinorrhea and postnasal symptoms for the child in the vignette makes sinusitis unlikely.
Atypical pneumonia caused by Mycoplasma pneumoniae and Chlamydia pneumoniae may present at any age, although it is unusual prior to age 3 years. The patient’s age and the absence of characteristic constitutional symptoms, such as fever, malaise, and headache, make this diagnosis unlikely.
Cough can represent the sole manifestation of GER, but infant reflux usually becomes symptomatic during the first few postnatal months and improves by 12 months. GER may worsen at night during supine positioning, but exercise and upper respiratory tract infections are uncommon precipitating factors for GER symptoms.
------------------------------------------------------------------------------------
Q 2:
A mother brings in her 13-month-old daughter for evaluation because her girl developed a perioral rash and "hives" on two occasions last week. One episode occurred while eating yogurt and another happened immediately after eating a bagel with cream cheese. She states that her daughter has eaten other foods such as eggs and bread without problems but is breastfeeding and never has been given milk-based formulas or cow milk. The infant has been given rice milk, but she became fussy and seems to prefer breastfeeding. The mother is concerned that her daughter may be allergic to milk but would like to stop breastfeeding.
Of the following, the BEST advice is to recommend
A. a cow milk food challenge in the clinic
B. avoidance of milk, egg, soy, and wheat products
C. breastfeeding until the child is 3 years old
D. switching to an amino acid-based formula
E. switching to soy milk
Answer :
E
if the question said : Of the following, the most safe line of management is to recommend
The answer will be :
D
Taking a detailed history about the specific food(s) involved, timing of the onset of symptoms, and type of
symptoms is important to distinguish IgE-mediated reactions, as described for the child in the vignette, from other adverse milk reactions, such as milk protein enterocolitis and lactose intolerance.
Once an IgE-mediated food allergy is suspected, the clinician should consider allergy skin testing or serum IgE testing for the suspected food.
While awaiting results from either blood testing or allergy consultation for skin testing, the first reasonable action is to switch to a soy-based formula.
Approximately 10% to 15% of infants and children who have IgE-mediated milk protein allergies may not tolerate soy formula, but this risk applies to infants younger than 6 months of age. For infants older than 6 months, the risk is closer to 5%.
Nonetheless, the initial soy formula trial should be performed in the clinic.
Other acceptable formula options in this scenario include an extensively hydrolyzed or an amino acidbased
formula, although the unpleasant taste and significantly higher cost can be limiting for many families. Also, because almost all affected infants can be fed successfully with a soy or extensively hydrolyzed formula, switching initially to an amino acid-based formula is not required.
Some experts go directly to use completely hydrolyzed formulas to avoid the development of allergy to soy milk which can occur in some cases.
---
From Elzouki Textbook of clinical pediatrics 2012
Some 0.5–7.5% of infants have a true allergy to the cow’s milk proteins that are in cow’s milk-based formulas.
Infants with true cow’s milk allergy can develop abdominal pain, diarrhea, rectal bleeding, skin rash, and wheezing when given milk-based formulas. These symptoms will disappear as soon the milk-based formula is removed from the diet. Since allergy to cow milk protein is different from lactose intolerance, treatment of cow milk protein allergy involves using formulas that are not based on cow’s milk or using formulas that contain ‘‘predigested’’ casein and whey proteins.
The predigesting process breaks the whole proteins into smaller pieces or into amino acids.
Soy-protein formulas contain no cow’s milk, and are reasonable alternatives for infants with true cow’s milk
protein allergy. Since most soy-protein formulas also contain no lactose, they are also suitable for infants with
lactose intolerance. The carbohydrates in soy-protein formulas are sucrose, corn syrup solids, and cornstarch or glucose polymers.
------------------------
Q 3:
Answer :
D
The administration of antihistamines has been shown to be beneficial for patients who have a history of adverse reactions to radiocontrast media and need repeat studies.
E
if the question said : Of the following, the most safe line of management is to recommend
The answer will be :
D
Taking a detailed history about the specific food(s) involved, timing of the onset of symptoms, and type of
symptoms is important to distinguish IgE-mediated reactions, as described for the child in the vignette, from other adverse milk reactions, such as milk protein enterocolitis and lactose intolerance.
Once an IgE-mediated food allergy is suspected, the clinician should consider allergy skin testing or serum IgE testing for the suspected food.
While awaiting results from either blood testing or allergy consultation for skin testing, the first reasonable action is to switch to a soy-based formula.
Approximately 10% to 15% of infants and children who have IgE-mediated milk protein allergies may not tolerate soy formula, but this risk applies to infants younger than 6 months of age. For infants older than 6 months, the risk is closer to 5%.
Nonetheless, the initial soy formula trial should be performed in the clinic.
Other acceptable formula options in this scenario include an extensively hydrolyzed or an amino acidbased
formula, although the unpleasant taste and significantly higher cost can be limiting for many families. Also, because almost all affected infants can be fed successfully with a soy or extensively hydrolyzed formula, switching initially to an amino acid-based formula is not required.
Some experts go directly to use completely hydrolyzed formulas to avoid the development of allergy to soy milk which can occur in some cases.
---
From Elzouki Textbook of clinical pediatrics 2012
Some 0.5–7.5% of infants have a true allergy to the cow’s milk proteins that are in cow’s milk-based formulas.
Infants with true cow’s milk allergy can develop abdominal pain, diarrhea, rectal bleeding, skin rash, and wheezing when given milk-based formulas. These symptoms will disappear as soon the milk-based formula is removed from the diet. Since allergy to cow milk protein is different from lactose intolerance, treatment of cow milk protein allergy involves using formulas that are not based on cow’s milk or using formulas that contain ‘‘predigested’’ casein and whey proteins.
The predigesting process breaks the whole proteins into smaller pieces or into amino acids.
Soy-protein formulas contain no cow’s milk, and are reasonable alternatives for infants with true cow’s milk
protein allergy. Since most soy-protein formulas also contain no lactose, they are also suitable for infants with
lactose intolerance. The carbohydrates in soy-protein formulas are sucrose, corn syrup solids, and cornstarch or glucose polymers.
------------------------
Q 3:
A 10-year-old boy who has hypertension needs a contrast study of his kidneys. He is allergic to shrimp, and his parents are worried that he will have a reaction to the iodine content in the radiocontrast media.
Of the following, the MOST appropriate management is to:
A. perform allergy tests for radiocontrast media
B. pretreat the child with antihistamines and corticosteroids 1 week prior to the procedure
C. pretreat the child with antihistamines immediately before the procedure
D. reassure parents that the risk of reaction is negligible
E. undertake a food challenge with shrimp to confirm the diagnosis
Answer :
D
For most patients undergoing contrast studies, including the boy described in the vignette, no preventive therapy is needed prior to the study because the risk of anaphylaxis is low (0.04% to 0.36%(.
Pretreating a child with antihistamines and corticosteroids 1 week prior to the study is too long before the procedure. Pretreatment with only antihistamines is not adequate. There is no allergy testing for radiocontrast media because the trigger is the hypertonicity of the media. Evaluating for a shrimp allergy is not helpful because the adverse reactions are unrelated.
-------------------------------
Q4 :
A workup on an ill child revealed low levels of complement C3 in her blood. Which one of the following presentations did this child most likely manifest?
(A) Chronic eczema
(B) Immune hemolytic anemia
(C) Incomplete recovery from viral infections
(D) Poor response to vaccination
(E) Recurrent infections with extracellular bacteria
The answer :
E
Recurrent infections with extracellular bacteria. Complement proteins function in innate immunity through enzymatic cleavage of C3 to liberate C3b which directly binds to pathogen surfaces.
Following C3b insertion, enzyme cascade events result in lysis of the target cell by the membrane attack complex (complement protein scaffold C5–C9) and recruitment of phagocytes by C3a and C5a cleavage products.
Chronic eczema (choice A), immune hemolytic anemia (choice B), incomplete recovery from viral infections (choice C), and poor response to vaccination (choice D) would not involve complement pathways and thus would be unaffected by a C3 defi ciency.
--------------------------------------------------------------------
Q 5:
A 4-year-old child has atopic dermatitis due to severe allergies to dust, animal dander, and many kinds of pollens. Mediators released from which cell type are
responsible for the clinical manifestations immediately following exposure to these substances?
(A) B cells
(B) Macrophages
(C) Mast cells
(D) Th1 cells
(E) Th2 cells
The answer is
C
Mast cells. Allergens such as dust, animal dander, and pollen bind to IgE expressed on the surface of mast cells. Such IgE is produced during the fi rst exposure to the allergen and this IgE binds to high affi nity Fc receptors on mast cells.
This is known as sensitization. Secondary encounter with the allergen results in binding of the antigen to the IgE and activation of the mast cells (degranulation).
Macrophages (choice B) play a role in type IV delayed-type hypersensitivity. B cells (choice A) produce the initial antibodies (IgE) to the allergen but do not release vasoactive amines as does mast cells. Th1 cells (choice D) are the mediators of type IV hypersensitivity and Th2 cells (choice E) do promote the IgE production but again are not responsible for the mediators.
---------------------------------------------------------------------------------
Q 6:
An 8-month-old male has recurrent episodes of serious infections including otitis media, chronic sinusitis,
and bacterial pneumonia. He is diagnosed with X-linked agammaglobulinemia after an immunologic
workup. Which test result is consistent with this diagnosis?
(A) Absent CD16+ and CD54+ cells in peripheral blood
(B) Absent CD19+ and CD20+ cells in peripheral blood
(C) Absent serum IgG, very low levels of IgM
(D) Decreased CD3+ cells in peripheral blood
(E) Lymphopenia
Q 7:
Which infectious agents are most likely causing the recurrent infections in the child in the above case?
(A) Aspergillus fl avus and Candida albicans
(B) Chlamydia pneumoniae and Legionella pneumophila
(C) Haemophilus infl uenzae and Streptococcus pneumoniae
(D) Mycobacterium tuberculosis and Mycobacterium avium complex
(E) Pneumocystis jeroveci and Cryptosporidium hominis
Answer :
Q6 : The answer is B
Absent CD19+ and CD20+ cells in peripheral blood. X-linked agammaglobulinemia (XLA), also called Bruton agammaglobulinemia, is a congenital immune deficiency disease characterized by a lack of B-cell production by the bone marrow.
B cells express CD19 and CD20, and these two markers are exploited in flow cytometry studies to enumerate B cells in the peripheral blood. The lack of these cells in peripheral blood of a male infant is diagnostic for XLA.
Natural killer cells express CD16+ and CD54+ and are not affected in this disease.
Absent serum IgG, very low levels of IgM is inconsistent with XLA since without B cells no IgM could be produced. Infants with this disease have maternal IgG in their serum which declines at about 5 to 6 months of age, leaving them at increased risk for infections such as those seen in this patient. Infants with XLA have normal to elevated levels of CD3+ T cells. Lymphopenia is not seen, as the majority of circulating lymphocytes are T cells.
Q 7: The answer is C: Haemophilus infl uenzae and Streptococcus pneumoniae.
The absence of B cells and thus antibody makes an individual susceptible to those organisms controlled by humoral immune responses. The most important defenses against extracellular bacteria are opsonins (including IgG, in addition to complement C3b) and neutrophils.
The ability of neutrophils to phagocytize microorganisms is markedly enhanced when they are opsonized with both complement and IgG. Thus, a lack of IgG renders phagocytosis much less effi cient and increases the risk for infection with extracellular bacteria. H. infl uenzae and S. pneumoniae are two of the most important bacterial causes of otitis media, sinusitis, and pneumonia, and both are extracellular organisms.
Aspergillus fl avus and Candida albicans are both opportunistic fungi which cause infections in patients with profound neutropenia.
Patients with T-cell deficiencies also suffer serious infections with these organisms.
Chlamydia pneumoniae, Legionella pneumophila, and Mycobacterium sp. are intracellular bacteria. Legionnaires disease is seen most often in T-cell immune compromised patients, such as the elderly, transplant patients, or cancer patients.
Patients with disseminated Mycobacterium avium are profoundly T-cell immune suppressed.
On the other hand, both C. pneumoniae and Mycobacterium tuberculosis are able to infect immune competent individuals.
Pneumocystis jeroveci and Cryptosporidium hominis are pathogens that cause serious disease in the profoundly T-cell immune suppressed, including AIDS patients. P. jeroveci is a fungus, whereas C. hominis is a sporozoan parasite
-------------------------------------------------------
Q 8 :
A 12-year-old woman presents with airway obstruction secondary to laryngeal swelling. Her history
is significant for episodes of recurrent facial swelling . The swelling, which often involves the lips, begins suddenly without recognizable precipitating events and lasts for 2 to 3 days. Laboratory tests reveal a deficiency involving the complement system. Which component of the complement system is deficient in this
child?
(A) C1 inhibitor
(B) C3 convertase
(C) C5 convertase
(D) Mannose-binding lectin
(E) Membrane attack complex
The answer is A: C1 inhibitor.
This case is descriptive of hereditary angioedema, a condition attributed to a decrease in or dysfunction of C1 inhibitor (C1-INH).
This protein is a multifunction serine protease normally found in large amounts in serum. It binds to and inactivates C1r and C1s. It also inactivates proteins of the clotting and kinin systems. Decreased amounts of this protein result in subcutaneous and/ or submucosal edema through compromised inactivation of the complement and/or the kinin system. Hereditary angioedema is an autosomal dominant trait.
Deficiencies in the other complement components listed do not lead to hereditary angioedema.
--------------------------------------------------
Q10:
-------------------------------
Q4 :
A workup on an ill child revealed low levels of complement C3 in her blood. Which one of the following presentations did this child most likely manifest?
(A) Chronic eczema
(B) Immune hemolytic anemia
(C) Incomplete recovery from viral infections
(D) Poor response to vaccination
(E) Recurrent infections with extracellular bacteria
The answer :
E
Recurrent infections with extracellular bacteria. Complement proteins function in innate immunity through enzymatic cleavage of C3 to liberate C3b which directly binds to pathogen surfaces.
Following C3b insertion, enzyme cascade events result in lysis of the target cell by the membrane attack complex (complement protein scaffold C5–C9) and recruitment of phagocytes by C3a and C5a cleavage products.
Chronic eczema (choice A), immune hemolytic anemia (choice B), incomplete recovery from viral infections (choice C), and poor response to vaccination (choice D) would not involve complement pathways and thus would be unaffected by a C3 defi ciency.
--------------------------------------------------------------------
Q 5:
A 4-year-old child has atopic dermatitis due to severe allergies to dust, animal dander, and many kinds of pollens. Mediators released from which cell type are
responsible for the clinical manifestations immediately following exposure to these substances?
(A) B cells
(B) Macrophages
(C) Mast cells
(D) Th1 cells
(E) Th2 cells
The answer is
C
Mast cells. Allergens such as dust, animal dander, and pollen bind to IgE expressed on the surface of mast cells. Such IgE is produced during the fi rst exposure to the allergen and this IgE binds to high affi nity Fc receptors on mast cells.
This is known as sensitization. Secondary encounter with the allergen results in binding of the antigen to the IgE and activation of the mast cells (degranulation).
Macrophages (choice B) play a role in type IV delayed-type hypersensitivity. B cells (choice A) produce the initial antibodies (IgE) to the allergen but do not release vasoactive amines as does mast cells. Th1 cells (choice D) are the mediators of type IV hypersensitivity and Th2 cells (choice E) do promote the IgE production but again are not responsible for the mediators.
---------------------------------------------------------------------------------
Q 6:
An 8-month-old male has recurrent episodes of serious infections including otitis media, chronic sinusitis,
and bacterial pneumonia. He is diagnosed with X-linked agammaglobulinemia after an immunologic
workup. Which test result is consistent with this diagnosis?
(A) Absent CD16+ and CD54+ cells in peripheral blood
(B) Absent CD19+ and CD20+ cells in peripheral blood
(C) Absent serum IgG, very low levels of IgM
(D) Decreased CD3+ cells in peripheral blood
(E) Lymphopenia
Q 7:
Which infectious agents are most likely causing the recurrent infections in the child in the above case?
(A) Aspergillus fl avus and Candida albicans
(B) Chlamydia pneumoniae and Legionella pneumophila
(C) Haemophilus infl uenzae and Streptococcus pneumoniae
(D) Mycobacterium tuberculosis and Mycobacterium avium complex
(E) Pneumocystis jeroveci and Cryptosporidium hominis
Answer :
Q6 : The answer is B
Absent CD19+ and CD20+ cells in peripheral blood. X-linked agammaglobulinemia (XLA), also called Bruton agammaglobulinemia, is a congenital immune deficiency disease characterized by a lack of B-cell production by the bone marrow.
B cells express CD19 and CD20, and these two markers are exploited in flow cytometry studies to enumerate B cells in the peripheral blood. The lack of these cells in peripheral blood of a male infant is diagnostic for XLA.
Natural killer cells express CD16+ and CD54+ and are not affected in this disease.
Absent serum IgG, very low levels of IgM is inconsistent with XLA since without B cells no IgM could be produced. Infants with this disease have maternal IgG in their serum which declines at about 5 to 6 months of age, leaving them at increased risk for infections such as those seen in this patient. Infants with XLA have normal to elevated levels of CD3+ T cells. Lymphopenia is not seen, as the majority of circulating lymphocytes are T cells.
Q 7: The answer is C: Haemophilus infl uenzae and Streptococcus pneumoniae.
The absence of B cells and thus antibody makes an individual susceptible to those organisms controlled by humoral immune responses. The most important defenses against extracellular bacteria are opsonins (including IgG, in addition to complement C3b) and neutrophils.
The ability of neutrophils to phagocytize microorganisms is markedly enhanced when they are opsonized with both complement and IgG. Thus, a lack of IgG renders phagocytosis much less effi cient and increases the risk for infection with extracellular bacteria. H. infl uenzae and S. pneumoniae are two of the most important bacterial causes of otitis media, sinusitis, and pneumonia, and both are extracellular organisms.
Aspergillus fl avus and Candida albicans are both opportunistic fungi which cause infections in patients with profound neutropenia.
Patients with T-cell deficiencies also suffer serious infections with these organisms.
Chlamydia pneumoniae, Legionella pneumophila, and Mycobacterium sp. are intracellular bacteria. Legionnaires disease is seen most often in T-cell immune compromised patients, such as the elderly, transplant patients, or cancer patients.
Patients with disseminated Mycobacterium avium are profoundly T-cell immune suppressed.
On the other hand, both C. pneumoniae and Mycobacterium tuberculosis are able to infect immune competent individuals.
Pneumocystis jeroveci and Cryptosporidium hominis are pathogens that cause serious disease in the profoundly T-cell immune suppressed, including AIDS patients. P. jeroveci is a fungus, whereas C. hominis is a sporozoan parasite
-------------------------------------------------------
Q 8 :
A 12-year-old woman presents with airway obstruction secondary to laryngeal swelling. Her history
is significant for episodes of recurrent facial swelling . The swelling, which often involves the lips, begins suddenly without recognizable precipitating events and lasts for 2 to 3 days. Laboratory tests reveal a deficiency involving the complement system. Which component of the complement system is deficient in this
child?
(A) C1 inhibitor
(B) C3 convertase
(C) C5 convertase
(D) Mannose-binding lectin
(E) Membrane attack complex
The answer is A: C1 inhibitor.
This case is descriptive of hereditary angioedema, a condition attributed to a decrease in or dysfunction of C1 inhibitor (C1-INH).
This protein is a multifunction serine protease normally found in large amounts in serum. It binds to and inactivates C1r and C1s. It also inactivates proteins of the clotting and kinin systems. Decreased amounts of this protein result in subcutaneous and/ or submucosal edema through compromised inactivation of the complement and/or the kinin system. Hereditary angioedema is an autosomal dominant trait.
Deficiencies in the other complement components listed do not lead to hereditary angioedema.
--------------------------------------------------
Q10:
A 6-month-old male is hospitalized with disseminated Mycobacterium avium complex. His history
is signifi cant for recurrent episodes of otitis media which responded poorly to antibiotics and episodes
of severe thrush and diaper rash. Based on this history, an immunologic workup was done and the child
was diagnosed with an immune defi ciency disorder. Defi ciencies of which aspect of the immune response
could best account for the child’s medical history?
(A) B cells
(B) B and T cells
(C) Complement
(D) Macrophages
(E) Neutrophils
The answer :
B: B and T cells
Control of intracellular pathogens is primarily dependent on intact cell-mediated immunity and control of extracellular pathogens is primarily dependent on intact humoral immunity. The pathogens causing disease in this child include both intracellular and extracellular organisms.
Disseminated M. avium complex infections occur in patients with compromised cell-mediated immunity.
Organisms causing otitis media requiring antibiotics are extracellular bacteria such as Streptococcus pneumoniae, Haemophilus inlfuenzae, or Moraxella catarrhalis.
The agent that causes thrush and diaper rash, Candida albicans, is controlled by phagocytes. Uncontrolled
growth of C. albicans occurs in patients with neutrophil dysfunctions or in patients whose T cells are
unable to activate phagocytic macrophages.
---------------------------------------
The next two questions are linked :
Q 11 :
A 10-month-old male with a history of recurrent, serious extracellular bacterial infections is hospitalized
with pneumonia due to Pneumocystis jeroveci. An immunologic workup reveals neutropenia, normal
numbers of T and B cells, normal complement levels and complement activity, elevated IgM and very
low IgG and IgA. What is the molecular defect in this disease?
(A) Defective expression by lymphocytes of adenosine deaminase
(B) Lack of Bruton tyrosine kinase
(C) Mutation of the γ-chain of the IL-2 receptor
(D) Mutation of the NADPH oxidase enzyme
(E) Reduced expression of CD154 on T cells
Q 12 :
What immunologic function is impaired in the child and best explains the infection in the above case?
(A) Antigen presentation by dendritic cells
(B) B-cell migration to follicles in secondary lymphoid tissue
(C) Differentiation of B and T cells from precursor cells
(D) Expression of functional antigen receptors on T cells
(E) T-cell activation of macrophages and class switching in B cells
Answer :
Q 10
The answer is E:
Reduced expression of CD154 on T cells.
This case is descriptive of hyper-IgM syndrome, a disease whose molecular defect is caused by mutations in the gene for CD40 ligand otherwise known as CD154.
Q 12
The answer is E:
T-cell activation of macrophages and class switching in B cells.
The case describes a child with T-cell dysfunction, as demonstrated by his infection with Pneumocystis jeroveci a fungal organism thought to be part of the normal oropharyngeal fl ora and that causes disease in patients with compromised T-cell–mediated immunity. As the T cells are normal in number, their activation must be impaired, and his current infection supports this idea.
The fact that the patient has elevated IgM and very low levels of IgG and IgA, suggests that the T cells cannot interact adequately with B cells to induce class switching.
In addition to cytokine stimuli, the interaction of CD40 on the B cell with CD40 ligand (also known as CD154) on the T cell is essential to stimulate class switching in B cells. This molecule is also essential for
-------------------
Q 13 :
A 4 year old male is admitted to the pediatric intensive care unit with respiratory distress secondary to an acute exacerbation of asthma. He was started on albuterol as a continuous nebulized solution of 10 mg/h. He is awake and agitated, his oxygen saturation is 92% on 40% face mask oxygen, and he has normal inspiratory sounds. However, his Wood-Downes score is 7 because he has marked expiratory wheezing with maximal accessory muscle use. In light of these clinical fi ndings, it would be MOST important to initiate which of the following medications:
A. Azithromycin
B. Ipratroprium
C. Magnesium
D. Solumedrol
E. Theophylline
Answer :
D
Administration of Solumedrol ( methylprednisolone ) is very essential in this setting.
------------------------------------------
Q 14 :
Which of the following is not true about primary immune deficiency conditions :
A- Defective CD40L on helper T cells = inability to class switch - Hyper-lgM syndrome
B- Defect in B-cell maturation - Common variable immunodeficiency (CVID)
C- Th cells fail to produce I FN-gamma; inability of neutrophils to respond to chemotactic stimuli - Job's
syndrome)
D- Defect in BTK, a tyrosine kinase gene blocks pro-B cells from forming pre-B cells - Bruton's
agammaglobulinemia
E- 21q l l deletion; failure to develop 3rd and 4th pharyngeal pouches - DiGeorge syndrome
Answer :
E
22q l l deletion; failure to develop 3rd and 4th pharyngeal pouches - DiGeorge syndrome
------------------------
Q 15 :
Answer :
E
A
Evaluating the boy in the vignette for milk
protein allergy probably is unnecessary because he admits to ingestion of
milk-containing foods without consequences. Placing the child on a lactose-free
diet not only can be therapeutic, but it also can be diagnostic. Avoiding milk
protein entirely or carefully reintroducing milk products is not necessary; it
is lactose that should be avoided or appropriate supplemental lactase should be
used. The child does not require an epinephrine prescription because lactose
intolerance does not have an anaphylactic potential
-------------------------------------
Q 17:
Answer :
A
An allergy to pollens occurs only after repeated exposures and, thus, is rare before age 3 years. Because there are virtually no grass pollens in the northern United States in December, it is nearly impossible for a child, such as the boy in the vignette, to have symptoms due to grass pollen allergy. Children who will be atopic commonly become so by the age of 5 years.
Children as young as 2 years of age can have allergies to animal dander and pollens, but usually they require significant exposure to develop reactions. Examples of significant exposure include having multiple pets in the home or a family member who is a landscaper or gardener and, thus, brings pollen into the home on his or her clothes. It is unlikely that the child described in the vignette has obstructive adenoidal tissue because his symptoms are intermittent. Thus, an adenoidectomy is not appropriate treatment. Referring the child to an allergist for allergy skin testing for pollens would not be appropriate because it is unlikely that the child has a pollen allergy. Many medications can be used to treat allergic symptoms in children, but none is approved for children younger than 2 years of age.
---
Q18
----
Q 19
is signifi cant for recurrent episodes of otitis media which responded poorly to antibiotics and episodes
of severe thrush and diaper rash. Based on this history, an immunologic workup was done and the child
was diagnosed with an immune defi ciency disorder. Defi ciencies of which aspect of the immune response
could best account for the child’s medical history?
(A) B cells
(B) B and T cells
(C) Complement
(D) Macrophages
(E) Neutrophils
The answer :
B: B and T cells
Control of intracellular pathogens is primarily dependent on intact cell-mediated immunity and control of extracellular pathogens is primarily dependent on intact humoral immunity. The pathogens causing disease in this child include both intracellular and extracellular organisms.
Disseminated M. avium complex infections occur in patients with compromised cell-mediated immunity.
Organisms causing otitis media requiring antibiotics are extracellular bacteria such as Streptococcus pneumoniae, Haemophilus inlfuenzae, or Moraxella catarrhalis.
The agent that causes thrush and diaper rash, Candida albicans, is controlled by phagocytes. Uncontrolled
growth of C. albicans occurs in patients with neutrophil dysfunctions or in patients whose T cells are
unable to activate phagocytic macrophages.
---------------------------------------
The next two questions are linked :
Q 11 :
A 10-month-old male with a history of recurrent, serious extracellular bacterial infections is hospitalized
with pneumonia due to Pneumocystis jeroveci. An immunologic workup reveals neutropenia, normal
numbers of T and B cells, normal complement levels and complement activity, elevated IgM and very
low IgG and IgA. What is the molecular defect in this disease?
(A) Defective expression by lymphocytes of adenosine deaminase
(B) Lack of Bruton tyrosine kinase
(C) Mutation of the γ-chain of the IL-2 receptor
(D) Mutation of the NADPH oxidase enzyme
(E) Reduced expression of CD154 on T cells
Q 12 :
What immunologic function is impaired in the child and best explains the infection in the above case?
(A) Antigen presentation by dendritic cells
(B) B-cell migration to follicles in secondary lymphoid tissue
(C) Differentiation of B and T cells from precursor cells
(D) Expression of functional antigen receptors on T cells
(E) T-cell activation of macrophages and class switching in B cells
Answer :
Q 10
The answer is E:
Reduced expression of CD154 on T cells.
This case is descriptive of hyper-IgM syndrome, a disease whose molecular defect is caused by mutations in the gene for CD40 ligand otherwise known as CD154.
Q 12
The answer is E:
T-cell activation of macrophages and class switching in B cells.
The case describes a child with T-cell dysfunction, as demonstrated by his infection with Pneumocystis jeroveci a fungal organism thought to be part of the normal oropharyngeal fl ora and that causes disease in patients with compromised T-cell–mediated immunity. As the T cells are normal in number, their activation must be impaired, and his current infection supports this idea.
The fact that the patient has elevated IgM and very low levels of IgG and IgA, suggests that the T cells cannot interact adequately with B cells to induce class switching.
In addition to cytokine stimuli, the interaction of CD40 on the B cell with CD40 ligand (also known as CD154) on the T cell is essential to stimulate class switching in B cells. This molecule is also essential for
-------------------
Q 13 :
A 4 year old male is admitted to the pediatric intensive care unit with respiratory distress secondary to an acute exacerbation of asthma. He was started on albuterol as a continuous nebulized solution of 10 mg/h. He is awake and agitated, his oxygen saturation is 92% on 40% face mask oxygen, and he has normal inspiratory sounds. However, his Wood-Downes score is 7 because he has marked expiratory wheezing with maximal accessory muscle use. In light of these clinical fi ndings, it would be MOST important to initiate which of the following medications:
A. Azithromycin
B. Ipratroprium
C. Magnesium
D. Solumedrol
E. Theophylline
Answer :
D
Administration of Solumedrol ( methylprednisolone ) is very essential in this setting.
------------------------------------------
Q 14 :
Which of the following is not true about primary immune deficiency conditions :
A- Defective CD40L on helper T cells = inability to class switch - Hyper-lgM syndrome
B- Defect in B-cell maturation - Common variable immunodeficiency (CVID)
C- Th cells fail to produce I FN-gamma; inability of neutrophils to respond to chemotactic stimuli - Job's
syndrome)
D- Defect in BTK, a tyrosine kinase gene blocks pro-B cells from forming pre-B cells - Bruton's
agammaglobulinemia
E- 21q l l deletion; failure to develop 3rd and 4th pharyngeal pouches - DiGeorge syndrome
Answer :
E
22q l l deletion; failure to develop 3rd and 4th pharyngeal pouches - DiGeorge syndrome
------------------------
Q 15 :
A
2-year-old boy presents for evaluation of a chronic pruritic eruption. His
medical history is remarkable for recurrent epistaxis, otitis media, and
pneumonia. Physical examination reveals erythematous, slightly scaling patches
on the trunk and in the antecubital and popliteal fossae. Petechiae are present
profusely.
Of
the following, these findings are MOST suggestive of:
A. acrodermatitis
enteropathica
B. ataxia
telangiectasia
C. atopic
dermatitis
D. Langerhans
cell histiocytosis
E. Wiskott-Aldrich
syndrome
Answer :
E
The
triad of recurrent infections, bleeding (due to thrombocytopenia), and eczema reported for the boy in the vignette is characteristic of
Wiskott-Aldrich syndrome (WAS), an X-linked recessive disorder. Affected
children generally come to medical attention because of repeated episodes of
pneumonia or otitis media due to Streptococcus pneumoniae or Haemophilus
influenzae. However, sepsis or meningitis due to these organisms or infections
caused by opportunistic organisms also may occur. Predisposition to infection
is the result of a number of defects in both humoral and cell-mediated
immunity.
Patients who have WAS often have platelet counts in the range of 15
to 30 x 103/cu mm (15 to 30 x 109/L), and their platelets are abnormally small.
As a result, they experience bleeding that, at times, may be life-threatening
(eg, intracranial hemorrhage). The cutaneous findings are typical of atopic
dermatitis, although petechiae may be observed.
Acrodermatitis
enteropathica is an autosomal recessive disorder of zinc transport that
presents in infancy with diarrhea, failure to thrive, and rash. In contrast to
WAS, the eruption (Figure 47B) of acrodermatitis enteropathica consists of
erythematous, crusted patches around the mouth and eyes, on the distal
extremities, and in the perineum>
Patients
who have ataxia telangiectasia (an autosomal recessive disorder) may be
distinguished from those who have WAS by the presence of severe cerebellar
ataxia and telangiectasias involving the conjunctivae and skin. Other cutaneous manifestations include vitiligo, café au lait spots,
and premature graying of the hair.
------
Q 16
:
Answer :------
Q 16
:
The
mother of a 12-year-old boy who is new to your practice is concerned about her
son's milk allergy. At age 7, he developed symptoms of abdominal pain,
bloating, and flatulence after ingesting milk. He never has been evaluated
formally for the allergy, but his mother has been having him avoid milk
products to be safe. The child admits that he occasionally eats ice cream at
school without problems and only has symptoms if he consumes a large amount.
Of
the following, the MOST appropriate course of action is to:
A. allow
the child to eat only lactose-free dairy products
B. evaluate
the child for milk allergy
C. have
the child avoid all milk products diligently
D. have
the family reintroduce milk products gradually at home
E. prescribe
injectable epinephrine to the patient
A
When
a child has gastrointestinal symptoms after ingesting dairy products, a careful
history is necessary to determine if the symptoms are due to milk protein
allergy or lactose intolerance. A milk protein allergy is an immunoglobulin E
(IgE)-mediated event, with symptoms ranging from mild abdominal pain, vomiting,
and diarrhea to anaphylaxis and even death. Milk proteins also have been
associated with exacerbations of atopic dermatitis. These reactions usually
occur initially when the child is younger than 2 years of age, and symptoms may
be triggered by the ingestion of even minute amounts of diary products. In
fact, the only quantitative association in food allergy is that ingestion of
larger quantities can lead to more significant reactions.
Lactose
intolerance is caused by a deficiency of the enzyme lactase that breaks down
lactose, a disaccharide, into the monosaccharides, glucose and galactose. If
lactose is not appropriately digested, symptoms of abdominal pain, flatulence,
and bloating occur, as described for the child in the vignette. Because most
children who have lactose intolerance usually have some lactase, the occasional
ingestion of small amounts of lactose does not elicit a reaction. In contrast,
the child who has milk protein allergy often cannot tolerate even minute
amounts of milk product.
-------------------------------------
Q 17:
A
mother brings her 1-year-old son to your office because she thinks he is
allergic to grass pollen. He has had intermittent rhinitis for several months.
It is December, and the family lives in the northeast United States. Both
parents have seasonal allergic rhinitis.
Of
the following, your BEST advice to the mother is to:
A. begin
a long-acting antihistamine to control the boy’s symptoms
B. explain
that he does have allergies, but he cannot be treated until he is older
C. explain
that it is not allergy because of the boy’s age and exposure history
D. recommend
an adenoidectomy to relieve his symptoms
E. refer
the boy to an allergist for testing for sensitivity to grass pollens
Answer :
A
An allergy to pollens occurs only after repeated exposures and, thus, is rare before age 3 years. Because there are virtually no grass pollens in the northern United States in December, it is nearly impossible for a child, such as the boy in the vignette, to have symptoms due to grass pollen allergy. Children who will be atopic commonly become so by the age of 5 years.
Children as young as 2 years of age can have allergies to animal dander and pollens, but usually they require significant exposure to develop reactions. Examples of significant exposure include having multiple pets in the home or a family member who is a landscaper or gardener and, thus, brings pollen into the home on his or her clothes. It is unlikely that the child described in the vignette has obstructive adenoidal tissue because his symptoms are intermittent. Thus, an adenoidectomy is not appropriate treatment. Referring the child to an allergist for allergy skin testing for pollens would not be appropriate because it is unlikely that the child has a pollen allergy. Many medications can be used to treat allergic symptoms in children, but none is approved for children younger than 2 years of age.
---
Q18
The
mother of a 1-year-old child had suspected that he had symptoms of allergic
rhinitis, but you informed her that he probably did not because of his age and
exposure history. She returns 2 weeks later, unsatisfied with your explanation
because he has continued to have nasal discharge. The discharge now is yellow.
She would like a test performed to determine if her son has an infection or
allergic rhinitis.
Of
the following, the BEST test to perform is:
A. allergy
skin testing
B. limited
computed tomography of the sinuses
C. nasal
smear examination
D. rhinoscopy
E. serum
immunoglobulin E measurement
Answer
C
Answer
C
The
child described in the vignette has symptoms consistent with infectious
rhinosinusitis. Although children of this age have limited sinus development,
they still can suffer infectious rhinitis.
If
a diagnostic test is needed, the most efficient is examination of a nasal
smear. Neutrophils on the smear imply the presence of infection; eosinophils
suggest the diagnosis of allergy.
Allergy
skin testing for pollens or pets is not appropriate in children younger than 3
years of age. Limited computed tomography of the sinuses may be
helpful, but this procedure is extremely difficult to perform in a child of
this age, and the very small sinuses make it problematic to differentiate
between undeveloped sinuses and opacified ones. At this age, it also would be
difficult to evaluate the osteomeatal complex via rhinoscopy for the presence
of purulent material. An elevated immunoglobulin E concentration would not
confirm the diagnosis of allergy, and normal levels would not eliminate that
possibility.
----
Q 19
You
are seeing a 4-year-old girl in the emergency department for treatment of an
episode of anaphylaxis. She is currently taking amoxicillin for treatment of
otitis media. She had just finished lunch today and taken her medication when
she experienced respiratory difficulties, urticaria, and general discomfort.
Lunch included foods she normally eats, except for a new brand of chicken
noodle soup and plain M & M's for dessert. She does not like eggs, and when
she has eaten them in the past, she spat them out.
Of
the following, the MOST likely cause of her reaction is:
A. drug
allergy
B. food
allergy
C. food
poisoning
D. serum
sickness
E. viral
urticaria
Answer
B
--------------
Answer
B
The
child described in the vignette has classic symptoms of anaphylaxis:
respiratory difficulties, urticaria, and generalized discomfort. Many patients
who experience anaphylaxis describe an impending sense of doom. Studies have
demonstrated that patients who do not have an urticarial rash are at much
higher risk of death than those who have one.
The
most likely cause of this child’s anaphylaxis is a food allergy. Because she
has been receiving amoxicillin for several days, it is unlikely that the
reaction is due to that medication. The history of disliking eggs and usually
not eating them provides a clue to the potential food allergy; many children
who have a food allergy will refuse to eat the offending food long before the
food is identified as an allergen.
The
primary cause of anaphylaxis in children is foods; bee stings and drugs are
much less likely causative agents. The primary food allergens in infants and
toddlers are eggs, milk, wheat, and soy. Among older children, shellfish, fish,
nuts, and peanuts are also common triggers.
--------------
A
mother brings in her 2-month-old child, explaining that the infant was having
bloody diarrhea and abdominal distension while receiving milk-based formula.
Her brother-in law, who is a physician, tested the child and diagnosed milk
protein intolerance. She asks you what therapy should be started for this
intolerance.
Of
the following, the BEST treatment for milk protein intolerance is to:
A. administer
allergy immunotherapy for milk protein
B. allow
only small amounts of milk products
C. completely
avoid all milk products for 1 to 2 years
D. make
no dietary changes
E. only
allow milk proteins that have been cooked
Answer
C
Answer
C
The
appropriate therapy for the child who has gastrointestinal food
hypersensitivity to milk products is to avoid all milk products completely for
1 to 2 years. Patients who avoid the food have an excellent chance of
outgrowing the reaction. Allowing the patient to ingest small quantities of the
milk protein does not allow resolution of the disease. Some patients can
tolerate milk in the cooked form, but that would cause chronic exposure, which
would not allow resolution of the disease. At present, there is no allergy
immunotherapy for any foods.
.
Elimination of the offending foods leads to resolution of the symptoms within
72 hours, and readministration of food usually causes a return of symptoms
within 6 hours. However, patients who receive food challenges have a high
incidence of severe reactions.
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