Regional body composition and functional impairment in patients with myotonic dystrophy.

INTRODUCTION In this study we determined regional body composition in myotonic dystrophy (DM1) and able-bodied controls and evaluated the relationship between fat and lean tissue mass and functional impairment in DM1 patients. METHODS Dual-energy X-ray absorptiometry (DEXA) was used to obtain regional measurements of fat-free mass index (FFMI) and fat mass index (FMI) in 48 DM1 and anthropometrically matched control pairs. RESULTS DM1 patients had lower regional FFMI and higher FMI than controls (P < 0.01-0.001). In DM1 patients, total FMI increased significantly with increased muscular disability rating, decreased motor function measurement, and with both decreasing vital capacity and total lung capacity. Hypertriglyceridemia correlated with increasing FMI. CONCLUSIONS Regional FFMI is decreased in DM1, whereas FMI is underestimated by body mass index and is negatively correlated with patients' functional capacity. DEXA may provide valuable supporting evidence in the management of DM1.