Changes in bone metabolic parameters following oral calcium supplementation in an adult patient with vitamin D-dependent rickets type 2A.

Abstract

Vitamin D-dependent rickets type 2A (VDDR2A) is a rare inherited disorder with decreased tissue responsiveness to 1,25-dihydroxyvitamin D [1,25(OH)2D], caused by loss of function mutations in the vitamin D receptor (VDR) gene. Approximately 50 types of mutations have been identified so far that change amino acids in either the N-terminal DNA binding domain (DBD) or the C-terminal ligand binding domain (LBD) of the VDR protein. The degree of responsiveness to 1,25(OH)2D varies between patients with VDDR2A, which may depend on their residual VDR function. In this report, we describe a female patient with VDDR2A caused by an early stop codon (R30X) in the VDR gene that resulted in a severely truncated VDR protein. She developed alopecia and bowed legs within a year after birth and was diagnosed with rickets at the age of 2. She had been treated with active vitamin D and oral calcium supplementation until 22 years of age, when she developed secondary hyperparathyroidism and high bone turnover. The genetic diagnosis of VDDR2A promoted the discontinuation of active vitamin D treatment in favor of monotherapy with oral calcium supplementation. We observed amelioration of the secondary hyperparathyroidism and normalization of bone metabolic parameters within 6 years.

• Authors: Yuka Kinoshita, Nobuaki Ito, Noriko Makita, Masaomi Nangaku, Seiji Fukumoto
• Journal: Endocrine journal (Endocr J) Vol. 64 Issue 6 Pg. 589-596 (Jun 29 2017) ISSN: 1348-4540 [Electronic] Japan
• PMID: 28367941 (Publication Type: Case Reports, Journal Article)

Chemical References

• Calcium, Dietary
• Codon, Terminator
• Receptors, Calcitriol
• VDR protein, human

Topics

• Adult
• Alopecia (etiology)
• Bone and Bones (metabolism)
• Calcium, Dietary (therapeutic use)
• Codon, Terminator
• Dietary Supplements
• Familial Hypophosphatemic Rickets (diet therapy, genetics, metabolism, physiopathology)
• Female
• Humans
• Hyperparathyroidism, Secondary (etiology, prevention & control)
• Mutation
• Receptors, Calcitriol (genetics)
• Treatment Outcome
• Young Adult