Periarticular Hyperphosphatemic Familial Tumoral Calcinosis in a Saudi Patient: A Case Report.

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder characterized by ectopic calcifications in periarticular soft tissues due to mutations in genes such as GALNT3, FGF23, or KL, leading to FGF23 deficiency or resistance and subsequent hyperphosphatemia. This study describes a 12-year-old girl from Jazan, Saudi Arabia, who presented with progressive right hip pain and swelling, initially managed as an infection. Imaging revealed periarticular calcifications, and laboratory tests confirmed hyperphosphatemia with normal calcium and parathyroid hormone levels. Genetic testing identified a homozygous pathogenic variant in GALNT3, confirming HFTC type 1. Recurrence occurred 1.5 years later in the right elbow, with similar radiographic findings. Further evaluation via CT demonstrated basal ganglia and parotid gland calcifications, highlighting systemic involvement. Management included complete surgical resection of calcific deposits, followed by acetazolamide (500 mg twice daily) and a low-phosphorus diet. Over one year of multidisciplinary follow-up, no recurrence was observed. Histopathology revealed microcalcifications with a giant cell reaction, consistent with HFTC. HFTC's diagnosis relies on clinical, biochemical (hyperphosphatemia), and radiological findings (multilobulated periarticular calcifications), supplemented by genetic testing. Treatment involves phosphate-lowering strategies (dietary restriction, phosphate binders, acetazolamide) and surgical excision for symptomatic lesions. This study underscores the importance of early recognition, genetic confirmation, and a multidisciplinary approach to prevent complications and recurrence.