A 15-year-old girl evaluated for short stature has short fourth and fifth metacarpals, rounded facies, and subcutaneous ossifications. Serum calcium is 9.4 mg/dL, phosphate 3.4 mg/dL, and PTH 38 pg/mL (normal 15 to 65). Her mother has similar hand findings but normal biochemistry. What is the most likely diagnosis?
- A Pseudohypoparathyroidism type 1a
- B Pseudopseudohypoparathyroidism ✓
- C Idiopathic hypoparathyroidism
- D Vitamin D deficiency rickets
Correct answer: B. Pseudopseudohypoparathyroidism
Explanation
Albright hereditary osteodystrophy comprises short metacarpals, round facies, and ectopic ossification. When these features occur with normal serum calcium, phosphate, and PTH, the condition is pseudopseudohypoparathyroidism, caused by paternal transmission of the GNAS mutation. Pseudohypoparathyroidism type 1a shows the same phenotype plus end-organ resistance, giving hypocalcemia, hyperphosphatemia, and raised PTH. Vitamin D deficiency would raise PTH and lower calcium, neither seen here.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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