What is vitamin D-dependent rickets (type I)?

Updated: Jun 19, 2020
  • Author: Horacio B Plotkin, MD, FAAP; Chief Editor: Jatinder Bhatia, MBBS, FAAP  more...
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Answer

Answer

Also known as vitamin D–pseudodeficiency rickets (PDDR), this disorder results from a genetic deficiency in the enzyme that converts calcidiol to calcitriol in the kidney. Inheritance is autosomal recessive, and the gene is located in band 12q13.3. Clinical and laboratory examination findings are similar to those associated with nutritional rickets, with low levels of 1,25(OH)2 vitamin D.

Levels of 1,25(OH)2 vitamin D may be normal but inadequately low for the levels of calcium, phosphorus, and parathyroid hormone. These patients develop rickets despite receiving vitamin D at the recommended preventive doses.

Medical treatment consists of oral calcitriol (0.5-1.5mcg/day). These patients may also respond to pharmacologic doses of vitamin D (5,000-10,000U/day).


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