A 19-year-old woman has short stature, round face, obesity, short fourth and fifth metacarpals, subcutaneous ossifications, serum calcium 7.4 mg/dL, phosphate 5.6 mg/dL, and PTH 320 pg/mL. Her mother has identical hand findings. Which is the most likely diagnosis?
- A Pseudohypoparathyroidism type 1a ✓
- B Pseudopseudohypoparathyroidism
- C Nutritional vitamin D deficiency rickets
- D Chronic kidney disease with secondary hyperparathyroidism
Correct answer: A. Pseudohypoparathyroidism type 1a
Explanation
Albright hereditary osteodystrophy (round face, short metacarpals, subcutaneous ossification) combined with high PTH, low calcium, and high phosphate defines pseudohypoparathyroidism type 1a, caused by maternal GNAS1 mutations producing end-organ resistance to PTH. Pseudopseudohypoparathyroidism shares the phenotype but has normal calcium and PTH. Vitamin D deficiency lowers or keeps phosphate low-normal, and CKD would show renal impairment, neither of which fits here.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.