Bone mineral metabolism in patients with neurofibromatosis type 1 (von Recklingausen disease).

The neurofibromatosis type 1 (NF1) is characterized by specific cutaneous features (neurofibromas, "café-au-lait" spots of the skin) and alterations of several tissue (nervous, vascular) and bone deformities, such as scoliosis, congenital pseudoarthrosis and bone dysplasia of tibia. Moreover, several studies have shown systemic involvement of bone tissue in NF1 patients, leading to reduced bone mass. The aim of our study was to evaluate some bone mineral metabolism parameters before and after calcium and vitamin D supplementation in NF1 patients. We evaluated in 70 NF1 consecutive patients the mineral metabolism and bone mineral density compared with 40 normal subjects. We showed bone alterations in 35% of patients and the increase of bone formation markers, such as bone isoenzyme of alkaline phosphatase (41.2 ± 15.5 vs. 25.6 ± 8.7 UI; P < 0.05, respectively) and osteocalcin (18.1 ± 5.6 vs. 7.6 ± 1.9 ng/ml; P < 0.05) and reduction of circulating levels of (25OH)-vitamin D (21.8 ± 12.3 ng/ml) with an high percentage of hypovitaminosys D (>60%). Moreover, we revealed a significant reduction of bone mass density at spine (L1-L4) (0.935 ± 0.13 vs. 1.110 ± 0.17 g/cm(2); P < 0.001) and femoral neck side (0.765 ± 0.09 vs. 0.839 ± 0.12 g/cm(2); P < 0.02), with high prevalence of osteopenia (44%) and osteoporosis (18%). After 12 months of calcium (1,200 mg/die) and cholecalciferol (800 UI/die) supplementation, we found a significant increase of (25) OH-vitamin D level (21.8 ± 12.3 vs. 35 ± 13 ng/ml; P < 0.01), without changes in bone mass density. In conclusion, NF1 patients may present a mineral bone involvement, with vitamin D deficiency; calcium and vitamin D supplementation is necessary to restore these bone mineral metabolic alterations.