Low Bone Mineral Density in Young Children with Cystic Fibrosis

Low bone mineral density (BMD) is a frequent problem for adult patients with cystic fibrosis (CF). Only limited information is available for young patients. The aim of this study was to evaluate BMD of children with CF younger than 6 years. BMD was measured at the lumbar spine (LS) after adjustment for height, sex, and pubertal status in 25 children with CF younger than 6 years, 53 prepubertal children aged 6 to 10 years, and 36 adolescents aged 11 to 18 years. Nutritional status, body composition, pulmonary disease severity, corticosteroid usage, dietary calcium, caloric intake, and vitamin D status were evaluated as potential correlates of BMD. The mean LS z score in the youngest group was significantly lower than normal (-0.96; SEM, 0.3). It did not differ significantly from that of children aged 6 to 10 years (-0.91; SEM, 0.2) or adolescents (-1.4; SEM, 0.2). LS z score was positively correlated with fat-free mass in multiple regression analysis. LS z score was less than -1 in 34% of the patients with mild pulmonary disease and normal nutritional status. These data suggest that the origin of CF bone disease in early childhood may be independent of nutritional status or disease severity.