Vitamin D Dependent Rickets Type 2A Due to a Rare Single Exon 3 VitaminD Receptor Gene Deletion in oddly unfortunate Siblings Presenting withAlopecia and Refractory Rickets: A rare Case Report

Abstract

Vitamin D-dependent rickets type 2A (VDDR2A) is a rare autosomal recessive disorder caused by pathogenic variants in the vitamin D receptor (VDR) gene, resulting in resistance to calcitriol. Congenital alopecia is an important clinical clue to this disorder. We report two female siblings with VDDR2A who presented with progressive rickets, growth retardation, and congenital alopecia. Both had previously received conventional vitamin D and calcium therapy for presumed nutritional rickets, without significant clinical improvement. Biochemical evaluation showed hypocalcemia, hypophosphatemia, elevated alkaline phosphatase, normal 25-hydroxyvitamin D, and elevated 1,25-dihydroxyvitamin D concentrations. Molecular genetic testing identified a deletion involving exon 3 of the VDR gene in both siblings, confirming the diagnosis. Despite prolonged treatment, both children demonstrated limited clinical and radiological improvement. Congenital alopecia in a child with refractory rickets should prompt consideration of VDDR2A. Recognizing the characteristic biochemical profile and confirming it early with molecular testing can support accurate diagnosis, appropriate management, and genetic counselling.