Pseudohypoparathyroidism Type 1B with Asymptomatic Hypocalcemia

ABSTRACT Objective: To report the rare case of an asymptomatic female patient with pseudohypoparathyroidism type 1b. Methods: The diagnosis of pseudohypoparathyroidism type 1b was confirmed by analysis of the methylation status by methylation-specific multiplex ligation-dependent probe amplification. Results: A 21-year-old female was referred to the endocrinology clinic due to an elevated parathyroid hormone level as an incidental finding. Her personal and family histories were unremarkable and there were no Albright hereditary osteodystrophy stigmata. Initially the patient only presented an elevated parathyroid hormone level, without hypocalcemia or hyperphosphatemia. The patient exhibited no signs or symptoms of hypocalcemia. After 6 months the patient presented hypocalcemia and treatment with calcium and calcitriol was commenced, despite her remaining asymptomatic. The genetic study was compatible with sporadic pseudohypoparathyroidism type 1b. Conclusion: An incidental finding of elevated parathyroid hormone with absence of Albright hereditary osteodystrophy phenotype raised the clinical suspicion of pseudohypoparathyroidism type 1b, which lead to careful monitoring of calcemia and therefore allowed timely management of hypocalcemia. Abbreviations: AHO Albright hereditary osteodystrophy GNAS guanine nucleotide binding protein, alpha stimulating gene Gsα alpha subunit of G protein PHP pseudohypoparathyroidism PHP-1a pseudohypoparathyroidism type 1a PHP-1b pseudohypoparathyroidism type 1b PHP-1c pseudohypoparathyroidism type 1c PHP-2 pseudohypoparathyroidism type 2 PTH parathyroid hormone