Case-control study of the muscular compartments and osseous strength in neurofibromatosis type 1 using peripheral quantitative computed tomography.

Skeletal anomalies are observed in neurofibromatosis type 1 (NF1), but the pathogenesis is unknown. Given that muscle mass is important in the development of the strength of bone, peripheral quantitative computed tomography (pQCT) was utilized to compare measurements of muscle compartments between NF1 individuals and controls. Forty individuals with NF1 (age 5-18 years) were evaluated. Cross-sectional measurements, at the 66% tibial site, were obtained using pQCT (XCT-2000, Stratec) and variables were compared to controls without NF1 ((age 5-18 years, N=380) using analysis-of-covariance controlling for age, height, Tanner stage, and gender. The NF1 cohort showed decreased total cross-sectional area [p<0.001], decreased muscle plus bone cross-sectional area [p<0.001], decreased muscle cross-sectional area [p<0.001], and decreased Stress Strain Index [p=0.010]. These data indicate that NF1 individuals have decreased muscle cross-sectional area and decreased bone strength than individuals without NF1.

Cortical bone geometry in asthmatic children.

At the mid-radius, pre-pubertal asthmatic children had smaller periosteal and endosteal circumferences and thicker cortical shells compared to controls, when assessed by peripheral quantitative computed tomography. Asthmatics had diminished periosteal expansion for muscle size, suggesting that asthma, its treatment, or its effects on physical activity had resulted in impaired adaptation of bone to muscle loading. Alterations in cortical bone geometry might explain the increased fracture risk in asthmatic children.