| Popis: |
A key event in the activation of vitamin D is its double-stage hydroxylation to form 1,25-(OH)2D, its hormonally active metabolite. Two primary inborn errors of vitamin D metabolism are known, pseudodeficiency rickets type I and type II. Pseudodeficiency rickets type I presumably results from a defect in the final enzymatic system leading to the formation of 1,25-(OH)2D. Its clinical, radiological, and most of its biological manifestations are similar to those observed in nutritional vitamin D deficiency. Complete healing can be achieved, provided that oral treatment with pharmacological doses of vitamin D or low doses of 1,25-(OH)2D3 or analogs is given during the patient’s entire life. Pseudodeficiency rickets type II results from a nonselective tissue resistance to 1,25-(OH)2D3. Its signs are rickets refractory to high doses of vitamin D and, in half of the cases, alopecia. Its pathological manifestations, alopecia excepted, may be overcome by extremely high doses of vitamin D derivatives or, in the most severe cases, by long-term calcium infusions or ultrahigh doses of oral calcium. |
