Bone Densitometry Measurements in Children with Neurofibromatosis Type 1 Using Quantitative Computed Tomography

Introduction: Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disease characterised by multisystemic involvement, including bone tissue. Deformities and reduced bone mass are the main bone manifestations in NF1. Quantitative computed tomography (QCT) provides true volumetric bone mineral density (BMD) measurement. This study aimed to evaluate bone metabolism parameters and BMD in children with NF1 using QCT.

Methods: The data of 52 paediatric NF1 patients (23 female, 29 male) was evaluated retrospectively. We investigated anthropometric measurements, biochemical parameters like total calcium, phosphate, magnesium, alkaline phosphatase, 25-hydroxyvitamin D (25OHD), parathyroid hormone, calcitonin, urinary calcium/creatinine ratio, and QCT parameters like lumbar trabecular and cortical BMD, trabecular area and cortical thickness. Comparisons of gender and puberty status were performed.

Results: 25% of patients had skeletal deformities and 42.3% had 25OHD inadequacy (<20 ng/mL). The frequency of 25OHD inadequacy was significantly higher in pubertal/postpubertal patients than prepubertal patients (61.9% vs. 29.0%, P = 0.019). Trabecular BMD Z-score was <-2.0 in 11.5% of patients; all with low BMD were at the pubertal/postpubertal stage. There was a significant negative correlation between age and trabecular Z-score (r = -0.41, P = 0.003). Mean cortical BMD was statistically similar between the genders and puberty groups. Puberty status, anthropometric Z-scores, and biochemical and QCT parameters were statistically similar between the genders (P > 0.05).

Conclusion: Paediatric NF1 patients may present with low BMD and 25OHD inadequacy, especially at puberty. QCT may be a useful tool to evaluate trabecular and cortical bone separately in NF1 patients.