Vitamin D status and muscle function in children with neurofibromatosis type 1 (NF1).

OBJECTIVES The aim of this cross-sectional study was to assess the vitamin D status and muscle function in children with NF1 compared with their unaffected siblings. METHODS NF1 children between 5 and 18 years of age and who had at least one unaffected sibling were identified. Serum concentrations of 25-hydroxyvitamin D (25(OH)D), calcium, inorganic phosphate, alkaline phosphate, parathyroid hormone and 1,25-dihydroxyvitamin D were measured. The Leonardo Mechanography Ground Reaction Force Platform (GRFP) was used to measure EFI, jump power, force and height. RESULTS There was no significant difference in 25(OH)D between NF1 subjects and unaffected siblings. Relative jump power and force were found to be significantly different. The adjusted means (95% confidence limits) of non-NF1 and NF1 children for relative jump power (W/kg), controlling for body mass and age, were 37.31 (34.14, 40.49) and 32.51 (29.34, 35.68), respectively (P=0.054); and force (N/kg), controlling for body mass, age and gender, were 25.79 (24.28, 27.30) and 21.12 (19.61, 22.63), respectively (P<0.0001). Jumping parameters were not related to serum 25(OH)D. CONCLUSIONS There was no significant relationship between vitamin D status and NF1 status in children. NF1 children had significantly impaired jumping power and force, when compared to their unaffected siblings.