Skeletal Complications With GNAS Mutation: An Unusual Case With Osteoma Cutis, Gout, and Synovial Chondromatosis in a Patient With Pseudopseudohypoparathyroidism

OBJECTIVE: We present a patient with pseudopseudohypoparathyroidism (PPHP) who developed both gout and synovial chondromatosis, in addition to the classical Albright’s hereditary osteodystrophy phenotype. METHODS: The patient’s clinical course, laboratory data, and imaging are presented. RESULTS: The patient is a 40-year-old male with no pertinent family history who presented with findings of Albright’s hereditary osteodystrophy, including short stature, obesity, rounded face, shortened fourth and fifth digits, and osteoma cutis (heterotopic subcutaneous ossification), which required surgical removal for pain relief. Genetic testing confirmed a GNAS mutation, and labs showed normal parathyroid hormone, calcium, and phosphorus levels, diagnostic of PPHP. The patient later developed gout and synovial chondromatosis, a rare benign process where the synovial membrane forms calcified loose bodies within the joint. CONCLUSION: The patient case highlights the musculoskeletal complications of PPHP. Though PPHP has been rarely associated separately with gout or synovial chondromatosis, this is the first reported patient to have developed both conditions. This case raises the significance of multidisciplinary follow up for potential orthopedic complications. Moreover, the case underscores the importance of genetics and epigenetics in skeletal health, independent of calcium homeostasis in the blood.