Identification of two novel mutations in the GALNT3 gene in a Chinese family with hyperphosphatemic familial tumoral calcinosis

Abstract

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare, autosomal recessive genetic disease. This disease is characterized by the progressive calcification of soft tissues leading to symptoms of pressure and hyperphosphatemia but normal concentrations of serum calcium with or without an elevation of 1,25-dihydroxyvitamin D₃ levels.HFTC is caused by loss-of-function mutations in the GALNT3, FGF23 or KL genes. Here, we identified two novel mutations in the GALNT3 gene in a Chinese family with HFTC. Identification of a novel genotype in HFTC provides clues for understanding the phenotype–genotype relationships in HFTC and may assist not only in the clinical diagnosis of HFTC but also in the interpretation of the genetic information used for prenatal diagnosis and genetic counseling.

Genetics: New mutations found for rare joint disease

Two new mutations have been linked to a rare disease characterized by abnormal deposits of phosphate and calcium. Hyperphosphatemic familial tumoral calcinosis (HFTC) results from an increase in the levels of phosphate in the blood and a progressive calcification of the soft tissues around joints, most often in the hips, shoulders and elbows. The calcium deposits can form masses that impair movement. A team led by Jianmin Liu and Xiaoyi Ding from the Shanghai Jiao-Tong University School of Medicine, China, describe two novel mutations in a gene called GALNT3 in a pair of Chinese siblings with HFTC. These findings, the first from a Chinese family clinically diagnosed with HFTC and confirmed by genetic analysis, should help in future diagnoses and in understanding the molecular causes of the disease.

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