Evaluation of bone abnormalities in children with neurojibromatosis type 1

Introduction
Bone abnormalities occur often in patients with neurofibromatosis type 1 (NF1). This suggests that the metabolism of bone tissue may be affected in these patients.

Objective
Evaluation of markers of bone mineral density and bone metabolism with respect to bone abnormalities in patients with NF1.

Methods
A total number of 57 NF1 patients and 145 controls were studied. Activity or concentrations of following markers of bone mineralization and bone metabolism were performed on all patients: bone-specific alkaline phosphatase (BAP), osteoprotegerin (OPG) and collagen type I crosslinked C-telopeptide (CTX).

Results
Bone abnormalities were observed in 75.44% NF1 patients. NF1 patients had a significant decrease in BMD z-score compared with controls (-0.679 ± 1.157 vs 0.000 ± 1.000 g/cm2, p < 0.0001). BAP activity was significantly higher in NF1 patients compared with controls (97.7 ± 46.2 vs 74.1 ± 29.7 U/l, p < 0.0001). CTX concentration for NF1 group was significantly higher compared with controls (1.89 ± 0.78 vs 1.45 ± 0.72 ng/ml, p = 0.002). No significant differences in OPG (3.94 ± 1.07 vs 3.72 ± 1.45 pmol/l) and sRANKL (0.147 ± 0.175 vs 0.148 ± 0.134 pmol/l) values were found between analyzed groups.

Conclusions
Sceletal defects often occurs in NF1 patients, with scoliosis being the most common pathology. NF1 can predispose to premature loss of bone mass. Analyzed markers indicate that bone resorption predominates over ossification in NF1 patients.