OMIA 000837 : Vitamin D-deficiency rickets, type IA

Possible human homologues (MIM numbers): 264700 (trait) , 609506 (gene)

Cross-species summary: Vitamin D (cholecalciferol) is synthesised in the skin from 7-dehydrocholesterol by the action of UV radiation from sunlight. Cholecalciferol, however, has very little biological activity: it requires two hydroxylations in order to become (biologically) active. The first hydroxylation, catalysed by cholecalciferol 25-hydroxylase, occurs in the liver. The second of these hydroxylations occurs in the kidney under the action of the enzyme 25-alpha-hydroxycholecalciferol 1-hydroxylase. The resultant active form of vitamin D (called 1,25-dihydroxycholecalciferol or 1,25(OH)sub2D) is a steroid hormone that plays a vital role in whole-body calcium homeostasis. Vitamin D-deficieny rickets, type 1A (previously known as Pseudo-vitamin D deficiency rickets) is an inherited deficiency of the 1-hydroxylase enzyme, due to mutations in the gene that encodes this enzyme, namely CYP27B1. As expected, this deficiency results in clinical signs indistinguishable from those seen in individuals suffering from non-genetic lack of vitamin D, most commonly resulting from a dietary deficiency of calcium or insufficient exposure to sunlight. The clinical signs of rickets (inherited and non-genetic) arise from defects in calcium homeostasis. The most noticeable effects include a failure of calcification of bones (leading to bowing of limbs) and delayed dentition.

Species in which this phene is found:
dog (Canis lupus familiaris)
domestic cat (Felis catus)
pig (Sus scrofa)

Edit History


  • Created by Frank Nicholas on 18 Jul 2006
  • Changed by Frank Nicholas on 30 Sep 2011
  • Changed by Imke Tammen2 on 10 Jul 2021
  • Changed by Imke Tammen2 on 06 Aug 2021
  • Changed by Imke Tammen2 on 25 Sep 2021