Familial Vitamin D-dependent rickets Type 2A: A report of two cases with alopecia and oral manifestations

摘要

Rickets is a metabolic bone disease that develops as a result of inadequate mineralization of growing bone due to disruption of calcium, phosphorus and/or Vitamin D metabolism. In addition, several rare genetic causes of rickets have also been described, which can be divided into two groups. The first group consists of genetic disorders of Vitamin D biosynthesis and action, such as Vitamin D-dependent rickets Type 1A, Type 1B, Type 2A (VDDR2A) and Type 2B. The second group involves genetic disorders of excessive renal phosphate loss (hereditary hypophosphatemic rickets). VDDR2A is a rare autosomal recessive disorder caused by mutation in the Vitamin D receptor gene, leading to end-organ resistance to 1,25(OH)sub2/subVitamin Dsub3/sub. It clinically represents growth retardation presenting in the 1supst/sup year of life and frequently associated with alopecia totalis, which differentiates it from VDDR Type 1. Due to target organ resistance, its response to Vitamin D is poor. We report two cases of familial VDDR2A, with alopecia and oral manifestations.