Effect of vitamin D3 treatment on bone density in neurofibromatosis 1 patients: a retrospective clinical study

Objectives We have previously demonstrated reduced bone density and an increased incidence of 25-hydroxy vitamin D3 (25-OH D3) deficiency in adults with neurofibromatosis 1 (NF1) compared to healthy controls. Vitamin D3 is a cheap, safe, and effective supplement in the general population, but its value in NF1 patients has not been demonstrated. This study investigates the therapeutic potential of oral vitamin D3 on bone mineral density (BMD) in NF1 patients with vitamin D3 deficiency. Methods We measured serum 25-OH D3, parathyroid hormone, calcium, and bone alkaline phosphatase concentrations, urinary deoxypyridinoline concentrations, and BMD in 35 adults with NF1. Nineteen patients received vitamin D3 supplementation for 2 years, six patients received supplementation for 1 year and 10 patients received no supplementation. Supplementation was administered in a dose that maintained the serum 25-OH D3 level above 30 μg/l. BMD was measured again at 1 and 2 years, and biochemical assessments of bone metabolism were measured at least every half year during therapy. Results Treated subjects had significantly reduced loss of BMD, as measured by T score at the hip (p = 0.011) and lumbar spine (p = 0.022). The effect on hip BMD was apparent at 1 year in comparison to baseline (p = 0.02) and was greater at 2 years in comparison to measurements at 1 year (p = 0.02). Conclusions Vitamin D3 supplementation improves BMD in adult NF1 patients. Further studies are needed to elucidate the mechanisms responsible for reduced BMD in NF1 patients.