Patterns of body composition and alteration after treatment in patients with newly diagnosed idiopathic inflammatory myopathies

Abstract

Objectives: To define the pattern of body composition and alteration after treatment of patients with newly diagnosed idiopathic inflammatory myopathies (IIMs) using DXA.

Methods: DXA was used to obtain regional and whole-body measurements of fat mass and lean tissue mass (LTM) in 50 patients with newly diagnosed IIM and matched controls. The DXA indices of fat mass and LTM were calculated. The analyses included correlations between DXA indices and clinical parameters [manual muscle test (MMT), Myositis Damage Index (MDI), Myositis Intention-to-Treat Activities Index (MITAX), handgrip, percentage forced vital capacity (%FVC) and creatine kinase level], comparison between patients with IIM and controls, comparison between IIM subgroups, receiver operating characteristic (ROC) analysis, and comparison of body composition before and after treatment.

Results: DXA LTM measurements were significantly correlated with MMT, MDI-muscle, handgrip strength, and %FVC. Patients with IIM had decreased LTM of the upper limbs and appendicular region. Male patients with IIM had significantly decreased LTM in the upper and lower limbs, whereas female patients with IIM had significantly decreased LTM in the upper limbs. Patients with IIM with anti-SRP seropositivity had lower LTM than patients with anti-SRP seronegativity. In ROC analysis, the DXA LTM indices presented good diagnostic values for distinguishing patients with newly diagnosed IIM from healthy controls. After treatment, the LTM of the upper limbs and appendicular region significantly increased.

Conclusion: DXA is an attractive method for the evaluation of patients with newly diagnosed IIM as well as a new way of monitoring disease conditions.

Keywords: body composition analysis; dual-energy X-ray absorptiometry; idiopathic inflammatory myopathy; prognosis.