A novel homozygous variant in exon 10 of the <i>GALNT3</i> gene causing hyperphosphatemic familial tumoral calcinosis in a family from North India

Hyperphosphatemic familial tumoral calcinosis (HFTC) is an extremely rare autosomal recessive disorder caused by variants in the GALNT3 (N-acetylgalactosaminyltransferase 3), FGF23 (Fibroblast Growth Factor-23) and αKL (α-Klotho) genes, which results progressive calcification of soft tissues. We describe case a 9-year-old girl who presented with recurrent hard nodular swellings on her feet knees intermittently discharged chalky white material. Her younger brother also had similar condition. Both siblings showed hyperphosphatemia, but parentsbiochemical parameters were normal. The histological features material aspirated from skin lesion consistent calcinosis. Sanger sequencing identified novel homozygous non-synonymous sequence variant exon 10 gene (NM_004482.3:c.[1681T>A];[1681T>A], NP_004473.2:p. [Cys561Ser];[Cys561Ser] proband affected brother. parents heterozygous carriers for same variant. In conclusion, we report new that HFTC North Indian family.