Repeated USMLE Questions Step 1 (83)

A 1-year-old boy is brought to the physician by his parents due to repeated upper respiratory tract infections and oral fungal infections. Physical examination reveals low set ears and fish-like mouth. Laboratory tests reveal hypocalcemia and chest x-ray shows no thymus shadow.

What is the most likely cause of hypocalcemia in this case?

A- Decreased secretion of parathyroid hormone

B- End-organ hyposensitivity to parathyroid hormone

C- End-organ hyposensitivity to calcitonin

D- Increased secretion of calcitonin

E- Increased secretion of parathyroid hormone


This case is most likely Di George syndrome. It is characterized by a defect in the third pharyngeal pouch which gives rise to inferior parathyroids and thymus.  The fourth pharyngeal pouch gives rise to superior parathyroids.

The correct answer is A

By | 2016-12-18T02:59:27+00:00 December 18th, 2016|USMLE Step 1|0 Comments

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