Endocrine Abstracts

JOINT979

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder characterized by progressive soft tissue calcifications due to a deficiency or resistance to intact fibroblast growth factor 23 (FGF23). The condition arises from pathogenic inactivating variants in the FGF23, GALNT3, or KLgenes. We present the case of a 10-year-old Omani girl diagnosed with HFTC. She initially presented with a gluteal mass and persistently elevated serum phosphate levels. Radiological investigations, including radiographs, computed tomography (CT), and magnetic resonance imaging (MRI), revealed a large, lobulated, calcified mass within the gluteus maximus muscle. A CT-guided biopsy of the mass demonstrated fibrous tissue with extensive dystrophic calcifications, consistent with tumoral calcinosis. Genetic testing identified a homozygous pathogenic variant in the GALNT3gene (c.484C>T, p.(Arg162*)), confirming the diagnosis. Despite therapeutic interventions aimed at lowering serum phosphate levels, poor compliance led to persistent hyperphosphatemia. This case underscores the challenges associated with the diagnosis and management of HFTC and highlights the importance of early detection, patient education, and adherence to treatment protocols to mitigate disease progression.