An 8-year-old boy has been admitted with cramping of his hands and feet that began with a recent illness. He has been healthy except for a chronic infection of his skin and nails for which he sees a dermatologist. Your physical exam of this normal appearing boy includes Chvostek’s and Trousseau’s signs, both of which are positive. Labs come back with a normal CBC, normal renal function, and electrolytes but a total serum calcium
of 7.2 mg/dL, phosphorus of 7.9 mg/dL, and an albumin of 3.9 g/dL.
What is the most likely diagnosis and what studies would you like to perform next?
What should your initial treatment be? What other illnesses do you need to be monitoring?
Answer :
Hypocalcemia in a school aged child. This child has symptomatic
hypocalcemia with a low serum calcium and high serum phosphorus. The high phosphorus
points to likely dysfunction of PTH secretion or function but the normal body habitus suggests that he does not have Albright’s Hereditary Osteodystrophy (AHO) as with pseudohypoparathyroidism. He does not have renal failure and the normal CBC makes tumor lysis less likely.
You look for hypomagnesemia that could cause this picture
but the magnesium level is normal and an EKG shows prolonged QT interval. Other studies that are sent off with the initial labs are PTH and 25(OH)D levels.
Because he is not having serious manifestations like seizures or tetany, you choose to start treatment with oral calcium to both raise the serum calcium and to act as a phosphate binder. You
choose a dose of 500 mg of elemental calcium four times daily as calcium carbonate and you place the patient on a low phosphate diet of 800 mg/day or less.
As soon as the phosphorus level starts to come down you start active 1,25(OH)2D at a “physiologic” dose of 0.5 mcg daily.
The PTH level comes back in the low normal range, which is
inappropriate for the level of calcium consistent with hypocalcemia and the 25(OH)D level is normal.
The rash turns out to be chronic Candida infection and the diagnosis of polyglandular autoimmune syndrome (PGA) type 1 is strongly suggested. Since a high percentage of PGA type 1 patients will go on to develop Addison’s disease, you must
carefully monitor for this potentially life-threatening condition, which can present with electrolyte abnormalities such as hyponatremia, hypokalemia, and acidosis.
A random cortisol of less than 18 μg/dL is suggestive of adrenal insufficiency but a cortisol stimulation test may be required. In addition to Addison’s disease, other disorders associated
with PGA 1 should be suspected if other clinical abnormalities develop.
