title: Extremely low serum pyridoxal 5'-phosphate in children with familial hypophosphatemic rickets.
abstract: The apparent vitamin B-6 status of 31 children with familial hypophosphatemic rickets (FHR) was determined. All children had alkaline phosphatase activity that was high-normal to elevated for their ages. A sensitive assay for pyridoxal 5'-phosphate (PLP) indicated that 15 of the 31 children had an undetectable (less than 0.2 nmol/L) concentration of the vitamer--the lowest values yet reported in human serum. The 16 remaining children had concentrations of the vitamer so low that they indicated a potential severe vitamin B-6 deficiency. However, none of the children had ever presented with any of the classical vitamin B-6-deficiency symptoms. Treatment of three additional FHR children with 100 mg pyridoxine.HCl/d resulted in a moderate and transient elevation of their serum PLP concentrations, a dramatic elevation of their erythrocyte PLP concentrations, and no improvement in clinical condition. Serum or plasma PLP concentrations are an inappropriate index for determining vitamin B-6 status in people with FHR and perhaps in others with elevated alkaline phosphatase activity.
authors.affiliation: Vitamin and Mineral Nutrition Laboratory, Beltsville Human Nutrition Research Center, US Department of Agriculture, MD 20705.
authors.forename: R D
authors.initials: RD
authors.lastname: Reynolds
authors.forename: R S
authors.initials: RS
authors.lastname: Lorenc
authors.forename: E
authors.initials: E
authors.lastname: Wieczorek
authors.forename: E
authors.initials: E
authors.lastname: Pronicka
mesh_terms: D000293:Adolescent; D000469:Alkaline Phosphatase / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000627:therapeutic use; D007015:Hypophosphatemia, Familial / Q000097:blood* / Q000150:complications / Q000188:drug therapy; D008297:Male; D010710:Phosphates / Q000627:therapeutic use; D011732:Pyridoxal Phosphate / Q000097:blood*; D011736:Pyridoxine / Q000627:therapeutic use; D012279:Rickets / Q000097:blood* / Q000150:complications / Q000188:drug therapy; D026681:Vitamin B 6 Deficiency / Q000097:blood / Q000150:complications* / Q000188:drug therapy
chemical_list: D006887:Hydroxycholecalciferols; D010710:Phosphates; D011732:Pyridoxal Phosphate; D000469:Alkaline Phosphatase; D011736:Pyridoxine; C008088:alfacalcidol