Pseudohypoparathyroidism with normocalcemia: a rare case report from Nepal

Pseudohypoparathyroidism (PHP), a rare genetic disorder is characterized by features of hypoparathyroidism due to tissue resistance to effect of parathyroid hormone (PTH).

A 1-year-old girl, the first child of healthy non-consanguineous parents with no family history of similar conditions or skeletal deformities, presented with small bumps on her leg, wrist, and periumbilical region for 6 months. Lab results revealed high serum phosphate, low vitamin D, normal calcium, and elevated PTH levels. Genetic testing identified a missense mutation in the GNAS gene, confirming a diagnosis of Albright osteodystrophy syndrome/progressive osseous heteroplasia. She was treated with vitamin D supplements and is on regular follow-up. The unusual case in this case is absence of family history and delayed clinical diagnosis.

PTH regulates calcium and phosphate levels by increasing blood calcium, reducing phosphate, and promoting the production of 1,25-dihydroxy-vitamin D (calcitriol). In pseudo-hypoparathyroidism (PHP), resistance to PTH in bones and kidneys leads to low calcium, high phosphate, and compensatory hyperparathyroidism. PHP often presents with hypocalcemia and hyperphosphatemia, but normocalcemia can occur due to effective compensatory mechanisms. A hallmark of Albright hereditary osteodystrophy, subcutaneous ossifications, can signal PHP. PHP type IA, linked to GNAS mutations, can present with elevated TSH at birth. Early diagnosis requires careful monitoring of calcium, phosphorus, PTH levels, and genetic testing. Management includes calcium and calcitriol supplementation with regular follow-up.

This case highlights the importance of diagnosing PHP, even in normocalcemic patients, when clinical signs like subcutaneous ossifications are present.