Pediatric generalized joint hypomobility and musculoskeletal complaints: a new entity? Clinical, biochemical, and osseal characteristics

To describe the clinical features, osseal characteristics, and collagen biochemistry in children who attended our clinic with predominantly generalized hypomobility of the joints, in combination with musculoskeletal complaints or abnormal walking, and no known syndrome or known rheumatic, neurologic, skeletal, metabolic, or connective tissue disorder was present. Nineteen children who attended the Children's Hospital of the University Medical Center Utrecht for generalized hypomobility of the joints (mean age: 11.6; standard deviation: 2.7), in combination with musculoskeletal complaints or abnormal walking as primary complaints (symptomatic generalized hypomobility [SGH]), were compared with an age-matched reference group of 284 healthy children with normal mobility of the joints. Anthropometrics, range of joint motion, muscle strength, exercise tolerance, motor development, quantitative ultrasound measurements of bone, and degradation products of collagen in urine were studied. Collagen modifications were determined in skin biopsies of 3 children and in hypertrophic scar tissue of another child, all with SGH. The range of joint motion was significantly decreased in almost all joints of all 19 children and after adjustment for age, gender, body weight, and height, significantly lower than that of the reference group (-108.3 degrees; 95% confidence interval [CI]: -136.9 to -79.8). Quantitative ultrasound measurements as well as urinary pyridinoline cross-link levels were, after adjustment for possible confounders, significantly lower in SGH children (broad-band ultrasound attenuation: -9.6 dB/MHz [95% CI: -17.4 to -1.9]; speed of sound: -25.0 m/s [95% CI: -39.7 to -10.3]; hydroxylysylpyridinoline: -50.1 micromol/mmol [95% CI: -87.6 to -12.6], lysylpyridinoline: -21.3 micromol/mmol [95% CI: -34.0 to -8.6]). An increased amount of pyridinoline cross-links per collagen molecule was observed in skin and hypertrophic scar tissue, in combination with increased amounts of collagen. SGH in children is considered a new clinical entity with specific clinical characteristics and might be related to an increased stiffness of connective tissue as a result of higher amounts of collagen with increased cross-linkin