Late diagnosis of hyperphosphatemic familial tumoral calcinosis in an adult male: lessons from a misclassified case.

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder caused by multiple genetic mutations; all leading to reduced FGF23 function. It is characterised by hyperphosphatemia, ectopic calcifications, and signs of systemic inflammation. We describe a case of a 33-year-old male patient, previously diagnosed to have tumoral calcinosis due to multiple calciferous masses, who presented with polyarthritis involving the joints of the hands. He was managed by multiple surgical resections, after which the masses and symptoms recurred. He lost follow-up for 16 years before presenting to our clinic. The identification of elevated serum phosphate levels and a sibling with similar symptoms guided the diagnosis of HFTC. The patient was started on a low phosphate diet, sevelamer, and acetazolamide, and was instructed to avoid calcium and vitamin D supplements. Intravenous Zoledronic Acid was also given. The patient reported improvement in his symptoms in the follow-up visits.