Vitamin D-dependent rickets type 2B with normal vitamin D receptor (VDDR2B) is an unusual form of rickets due to abnormal expression of a hormone response element-binding protein that interferes with the normal function of the vitamin D receptor. ... Vitamin D-dependent rickets type 2B with normal vitamin D receptor (VDDR2B) is an unusual form of rickets due to abnormal expression of a hormone response element-binding protein that interferes with the normal function of the vitamin D receptor. Vitamin D-dependent rickets type 2A (VDDR2A) is caused by mutation in the vitamin D receptor gene (VDR; 601769), and most patients have alopecia in addition to rickets. For a general phenotypic description and a discussion of genetic heterogeneity of rickets due to disorders in vitamin D metabolism or action, see vitamin D-dependent rickets type 1A (VDDR1A; 264700).
Giraldo et al. (1995) described an extraordinary incidence of vitamin D-dependent rickets type 2 associated with normal vitamin D receptor cDNA sequence in a rural area of the Cauca department in the southwest part of Colombia. More than ... Giraldo et al. (1995) described an extraordinary incidence of vitamin D-dependent rickets type 2 associated with normal vitamin D receptor cDNA sequence in a rural area of the Cauca department in the southwest part of Colombia. More than 200 black patients with different types of lower limb deformities were observed. The patients were well nourished and in good physical condition in spite of their lower limb deformities. None of them presented alopecia, myopathy, seizures, or aminoaciduria. Serum analysis showed significantly lower serum calcium than that in normal relatives, although in the low-normal range, normal phosphorus, high alkaline phosphatase, normal 25-hydroxyvitamin D3, and high 1,25-dihydroxyvitamin D3, indicating target organ resistance. Giraldo et al. (1995) suggested that these patients represented a distinct form of receptor-positive resistance to vitamin D. Specifically, they suggested that some posttranslational events may be involved in the VDR dysfunction in this family.