Bone mineral density in children and young adults with neurofibromatosis type 1
Maya B Lodish1, Urania Dagalakis, Ninet Sinaii
1Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. lodishma@mail.nih.gov
Insights
Children with neurofibromatosis type 1 (NF-1) often have impaired bone health. This study found lumbar spine bone density is particularly affected in pediatric NF-1 patients with high plexiform neurofibroma burden.
Area of Science:
- Pediatric Endocrinology
- Skeletal Biology
- Genetics
Background:
- Neurofibromatosis type 1 (NF-1) is a genetic disorder associated with various complications, including potential bone health issues.
- Children with NF-1, especially those with a significant plexiform neurofibroma burden, may be at higher risk for impaired bone development.
- Bone densitometry is increasingly utilized to assess skeletal health in pediatric populations with chronic conditions.
Purpose of the Study:
- To evaluate bone mineral apparent density (BMAD) and whole-body bone mineral content (BMC)/height in pediatric patients with NF-1.
- To investigate the relationship between plexiform neurofibroma burden and bone health parameters in this cohort.
- To identify specific skeletal sites most affected by impaired bone density in pediatric NF-1.
Main Methods:
- Sixty-nine pediatric and young adult patients with NF-1 were enrolled (age range 5.2-24.8 years).
- Hologic dual-energy X-ray absorptiometry (DXA) scans were performed to measure lumbar spine (LS 2-4), femoral neck (FN), and total body BMC/height.
- Bone mineral apparent density (BMAD) was calculated to normalize bone mineral density for bone volume, and Z-scores were determined. Impaired bone mineral density was defined as a Z-score ≤-2.
Main Results:
- Nearly half (47%) of patients exhibited impaired bone mineral density at any site.
- Lumbar spine (LS) showed the highest prevalence of impaired bone density (36%), followed by total body BMC/height (20%) and femoral neck (FN) (18%).
- Lumbar spine BMAD Z-scores were significantly more impaired (-1.60 ± 1.26) compared to the femoral neck (-0.54 ± 1.58) and total body BMC/height (-1.16 ± 0.90).
- A negative correlation was observed between plexiform neurofibroma burden and lumbar spine BMAD (r(s)=-0.36, P=0.01), indicating poorer bone density with higher tumor burden.
Conclusions:
- Pediatric and young adult patients with NF-1 frequently experience impaired bone health, particularly at the lumbar spine.
- The lumbar spine appears to be the most vulnerable skeletal site for bone density reduction in this population.
- Increased plexiform neurofibroma burden is associated with more severe impairment of lumbar spine bone mineral apparent density in NF-1 patients.
Abstract:
Concern for impaired bone health in children with neurofibromatosis type 1 (NF-1) has led to increased interest in bone densitometry in this population. Our study assessed bone mineral apparent density (BMAD) and whole-body bone mineral content (BMC)/height in pediatric patients with NF-1 with a high plexiform neurofibroma burden. Sixty-nine patients with NF-1 (age range 5.2-24.8; mean 13.7 ± 4.8 years) were studied. Hologic dual-energy X-ray absorptiometry scans (Hologic, Inc., Bedford, MA, USA) were performed on all patients. BMD was normalized to derive a reference volume by correcting for height through the use of the BMAD, as well as the BMC. BMAD of the lumbar spine (LS 2-4), femoral neck (FN), and total body BMC/height were measured and Z-scores were calculated. Impaired bone mineral density was defined as a Z-score ≤-2. Forty-seven percent of patients exhibited impaired bone mineral density at any bone site, with 36% at the LS, 18% at the FN, and 20% total BMC/height. BMAD Z-scores of the LS (-1.60 ± 1.26) were more impaired compared with both the FN (-0.54 ± 1.58; P=0.0003) and the whole-body BMC/height Z-scores (-1.16 ± 0.90; P=0.036). Plexiform neurofibroma burden was negatively correlated with LS BMAD (r(s)=-0.36, P=0.01). In pediatric and young adult patients with NF-1, LS BMAD was more severely affected than the FN BMAD or whole-body BMC/height.
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