Pseudohypoparathyroidism Type 1b with Digital Clubbing

Pseudohypoparathyroidism (PHP) is a rare disorder characterized by resistance to parathyroid hormone (PTH). Albright's hereditary osteodystrophy (AHO) is a characteristic physical condition associated with PHP. We herein report a 33-year-old Japanese man diagnosed with PHP type 1b who presented with hypocalcemia, preserved PTH secretion, decreased urinary cyclic adenosine monophosphate and phosphate excretion (Ellsworth-Howard test), deletion of exons 5-7 in STX16, hypomethylation of A/B-differentially methylated region (DMR) and AS1-DMR in the guanine nucleotide binding protein alpha stimulating gene. The patient did not have AHO or other comorbidities but showed digital clubbing during childhood. Although digital clubbing is rarely associated with PHP, it may represent a phenotype of this disorder.