MCQs In Muscular diseases

Q1 :

A 6-year-old boy has had difficulty walking and lower leg pain for 2 days. Five days ago, he had

fever and cough that had lasted for 3 days. On physical examination, the child has no fever, and

vital signs are normal, as are cranial nerves, speech, and language. Muscle bulk, tone, and

reflexes are normal and symmetric, but his lower legs are painful to palpation. Serum creatine

kinase is 2,000 U/L, and urine is negative for myoglobin.

Of the following, the MOST likely diagnosis is

A. dermatomyositis

B. Duchenne muscular dystrophy

C. Guillain-Barré syndrome

D. metabolic myopathy

E. viral myositis

Answer

E


A gait disturbance, such as described for the boy in the vignette, can result from a variety of
potentially serious disease processes and, therefore, requires urgent evaluation. The muscle
pain and otherwise normal neurologic findings prompted measurement of serum creatine kinase,
which can help to localize the problem rapidly. The prodrome of an upper respiratory tract illness
and rapid onset of symptoms is suggestive of viral myositis.

Dermatomyositis is a more indolent, chronic process and should not present acutely with
muscle pain. Moreover, dermatomyositis is characterized by specific skin findings such as the
heliotrope rash over the eyelids and Gottron papules .

 Duchenne muscular dystrophy presents with more chronic weakness. Although Guillain-Barré syndrome
can present with pain and weakness, the preserved reflexes, focal pain over the leg muscles, and elevated creatine kinase value are not consistent with that diagnosis. Metabolic myopathies due to mitochondrial dysfunction can present with acute pain, weakness, tender muscles, and rhabdomyolysis. However, the prevalence is much lower than viral myositis. Influenza A and B and enteroviruses may cause viral myositis.