Two cases of hyperphosphatemic familial tumoral calcinosis with varied etiology and unique presentations

ABSTRACT Hyperphosphatemic familial tumoral calcinosis is a rare disorder caused by fibroblast growth factor 23 (FGF23) deficiency or resistance resulting in elevated serum phosphorus levels in blood. Predominant clinical manifestations observed are ectopic calcification, hyperostosis, and rarely chronic recurrent multifocal osteomyelitis. It exhibits autosomal recessive inheritance and is associated with variants in three genes: FGF23 , GALNT3 , and KLOTHO. Recently, an acquired autoimmune variant has also been reported. In this report, we present two cases. One case presented with a clinical picture of chronic recurrent osteomyelitis and was found to have a variant in the GALNT3 gene. The other case exhibited typical manifestations but did not have an identifiable variant, and hence we are presuming it to be an acquired autoimmune variant.