A case of vitamin-D dependent type-1A rickets

Abstract

Abstract Rickets is a disease of growing bones characterized by softening of bones as a result of defective mineralization of cartilage in the epiphyseal growth plate. The predominant cause is a deficiency or impaired metabolism of vitamin D. Some forms of rickets do not respond to regular doses of cholecalciferol, which leads to suspicion of vitamin D-dependent rickets (VDDR). VDDR is of two types: type I is due to defective renal tubular 25-hydroxyvitamin D 1-α hydroxylase, and type II is due to end-organ resistance to the active metabolite of vitamin D. Here, we describe a child with seizures and calcipenic rickets with biochemical profile suggestive of VDDR type 1 worsened by phenytoin which responded completely to calcium and calcitriol supplementation. Whole exome sequencing revealed a heterozygous missense mutation in exon 7 of the TRPV4 gene (chromosome 12,c.1292C>A), whereas no mutations in CYP2R1, CYP27B1, VDR, and CYP3A4 were detected.