Hereditary Vitamin D Resistant Rickets: Clinical, Laboratory, and Genetic Characteristics of 2 Iranian Siblings

Hereditary vitamin D resistant rickets (HVDRR) is a rare disease that presents with signs and symptoms of rickets, alopecia, and growth retardation during the early years of life. The disease is caused by mutations in the vitamin D receptor (VDR) gene, which leads to unresponsiveness of the mutant receptor to 1-25(OH) 2 D3. The disease is transmitted as an autosomal recessive disorder and is found with equal frequency in males and females. The disease is rarely encountered and only about 100 cases are reported so far. The current paper reported the clinical and laboratory characteristics of 2 Iranian siblings with this disorder.They presented with rickets, growth retardation, muscle weakness, hypocalcemia and alopecia totalis since early childhood, and were followed up for 27 years. Sequencing of the DNA extracted from the peripheral white blood cells showed a missense G to A mutation in exon number 4 (g.30994 G > A) that led to the methionine substitution for the naturally occurring valine at position 26 in the DNA binding domain (DBD) of the VDR.