Disease Information for Rickets/X-linked hypophosphatemic: Definition

Metabolic defect, likely 1 alpha Hydroxylation on

25-hydroxylation of vitamin D; X-linked recessive familial rickets; Also called Vitamin D resistant type;

Nephrocalcinosis from overcorrected calcium intake

occurs; Males more sensitive; Short stature almost always

with bony deformity;type 2 below: ------------------------------------------------.HEREDITARY VITAMIN D-DEPENDENT RICKETS

Type I (pseudo-vitamin D deficiency) is an autosomal recessive syndrome, characterized by severe rickets, normal 25(OH)D3 and subnormal 1,25(OH)2D3 plasma levels, low or normal serum calcium, hypophosphatemia, and generalized aminoaciduria; This disorder results from absent or defective 1 -hydroxylase in the kidneys and responds to physiologic quantities of 1,25(OH)2D3 (1 to 2 µg/day) IV or po; Type II exists in several forms and is due to mutations in the 1,25(OH)2D3 receptor; This receptor, which is a transcription factor for 1,25(OH)2D3, causes expression of a variety of genes that control the metabolism of gut, kidney, bone, and other cells; The lack of a functional receptor produces a high but ineffective level of 1,25(OH)2D3; Some patients respond to very high doses of 1,25(OH)2D3 (10 to 40 µg/day); others do not respond at all; [Merck Manual 17th]

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