Normal Annual Increase of Bone Mineral Density During Two Years in Patients With Cystic Fibrosis

Abstract

Objectives. To determine prospectively for 2 years the change in bone mineral density (BMD) in patients with cystic fibrosis (CF) and to correlate clinical data and routine biochemical parameters of bone metabolism and infection with BMD.

Methods. Fifty-four patients with CF, aged 6 to 33 years, were included. BMD was measured using dual-energy x-ray absorptiometry in lumbar spine (LS) and femoral neck (FN). Anthropometric data and biochemical markers of bone metabolism and infection were measured. The number of intravenous antibiotic courses per year (ivAC) and pulmonary function were assessed.

Results. The patients had normal anthropometric data and normal growth, but 36% and 33% of the patients had BMD z score <−1 standard deviation in LS and in FN, respectively. Nevertheless, BMD increased at a normal rate during the 2 years and was correlated to weight and lung function. Intact parathyroid hormone was positively correlated with the increase of BMD in both LS and FN during childhood. Blood sedimentation rate, serum concentration of immunoglobulin G, and ivAC were negatively correlated with BMD in FN. Patients with 2 more severe CF transmembrane conductance regulator mutations had significantly lower BMD in FN than other genetic combinations.

Conclusion. The study suggests that low BMD in CF is multifactorial and depends on infection and nutritional parameters. Differences in BMD of LS and FN suggested higher susceptibility to infection in FN at all ages. Longitudinal studies starting early before bacterial colonization would be valuable to determine the relative role of infection in the development of BMD in CF.