Correlates of low bone mass in children with generalized forms of epidermolysis bullosa

Background Epidermolysis bullosa (EB) is a family of rare, heterogeneous, genetic disorders characterized by fragility of the skin and mucous membranes. Reduced bone mass and fractures have been recognized as complications of generalized forms of EB. Objectives We sought to describe the range and to estimate the prevalence of low bone mass in children with generalized EB, and to identify correlates of low bone mass in this population. Methods This was a prospective, observational study of 24 patients with generalized EB. Each patient completed a history, physical examination, laboratory studies, bone age, and x-rays of the lumbar spine. Those aged 6 years and older underwent dual energy x-ray absorptiometry scans of the lumbar spine. Primary outcomes were areal bone mineral density (aBMD) based on chronologic age, bone age, and adjusted for height Z-score. Descriptive statistics were used to summarize results, and linear regression was used to determine factors associated with low aBMD. Results Mean lumbar spine aBMD Z-scores ± SD were: –2.6 ± 1.4 for chronologic age, –1.7 ± 1.3 for bone age, and –1.0 ± 1.2 after adjusting for height Z-score. aBMD Z-scores were less than or equal to –2 in 64% for chronologic age, 50% for bone age, and 28% after adjusting for height Z-score. aBMD correlated with height Z-score, weight Z-score, extensive blistering, immobility, albumin, hemoglobin, iron, erythrocyte sedimentation rate, and c-reactive protein values. Limitations Small sample size was a limitation. Conclusions Children with severe, generalized recessive dystrophic EB have low aBMD for age. Deficits in aBMD were reduced after adjusting for delayed skeletal maturation and small body size.