What is the most likely cause of this patient's hypocalcemia?

A 1 0-year-old Hispanic male child without any significant past medical history is brought to the emergency department following an episode of generalized tonic-clonic seizures. His mother states that for the past year, his school performance has been deteriorating. He has been complaining of some muscle pain and cramps for the last two to three months. There is no history of trauma, fever, headache, vomiting, or cough. He has not seen a physician for the past five years. His vital signs are normal. Physical examination reveals a sedated child who is arousable on painful stimuli. He is prepubertal, without any dysmorphic features. His eye examination reveals pupils that are 3 mm in diame ter and normally reactive to light. He has bilateral cataracts. His heart, lungs, and abdomen are unremarkable. He moves all his extremities upon painful stimulation. His reflexes are hypoactive; plantars are equivocal. Lab investigations reveal a calcium level of 6.0 mg/dl (albumin 3.8 g/dl), phosphorus level of 8.2 mg/dl and PTH level of 150 pg/ml (normal 10 to 65 pg/ ml). Other labs are within normal limits. Non-contrast CT scan of the head shows basal ganglion calcification. What is the most likely cause of this patient’s hypocalcemia?

  • A. Vitamin D deficiency [1 3%]
  • B. Hypoparathyroidism [1 0%] .,
  • C. Pseudohypoparathyroidism [44%]
  • D. Pseudopseudohypoparathyroidism (PPHP) [1 6%]
  • E. Hyperphosphatemia [1 7%]

0 voters

This patient most likely has pseudohypoparathyroidism. He has longstanding hypocalcemia with hyperphosphatemia, as evidenced by bilateral cataracts and calcification of his basal ganglia (Fahr’s syndrome). Pseudohypoparathyroidism is due to the resistance of PTH on its target tissue. There are multiple types of pseudohypoparathyroidism. Type 1A has features of Albright hereditary osteodystrophy in addition to hypoparathyroidism. Albright hereditary osteodystrophy (AHO) is characterized by short stature, round facies, short fourth and fifth me tacarpals, and a short neck. This patient most likely has type 1 B pseudohypoparathyroidism, which does not have features of AHO.