Background Inflammatory myopathies (IM) are a multisystem diseases characterized by inflammation of skeletal muscles and skin. The skeletal muscle fascia forms a part of the muscle. In this study we investigated if inflammation of the fascia is present in inflammatory myopathies and whether this can be detected by ultrasound.
Objectives To assess fascia thickness of the deltoid and vastus lateralis (VL) muscles in healthy controls and IM patients.
Methods Healthy controls (n=54) and IM patients (n=9), diagnosed according to the Bohan and Peter criteria, were included. All scans were made in the transverse plane, unilateral with the Zonare Zone ultrasound device with a broad band linear 12-5 MHz transducer. The deep and superficial fascia of the VL and the superficial fascia of the deltoid muscle were measured at standardized anatomically defined location corresponding to the largest diameter of the muscle belly. Fascia thickness was measured with electronic calipers using a 2x magnification. They were placed at a interval of 0.25 cm with a maximum of 12 per scan. Fascii thickness of the healthy controls was correlated to age, height, weight and sex using a spearman’s rho correlation. Reference values were calculated. An unpaired Student’s t-test was used to determine the difference between IM patients and controls.
Results The median age of healthy controls was 52 years (range 22-87; 32 females) of IM patients 44 years (range 20-64; 5 females). The IM group consisted of n=5 dermatomyositis and n=4 polymyositis patients, the median disease duration was 3.3 years (range 1-23).
The intraobserver ICC’s were 0.6 (deltoid), 0.58 (superficial fascia VL) and 0.8 (deep fascia VL). Interobserver ICC’s were 0.29, 0.49 and 0.86.
Mean muscle fascia thickness in healthy controls was 0.54 mm of the deltoid muscle and 1.28 and 1.33 mm of the superficial and deep fascii of the vastus lateralis muscle respectively (table 1). There was a small but significant increase of the deep fascia thickness of the VL with increasing weight (r =0.38). Age, sex and height did not influence fascia thickness. Fascia thickness of the deltoid muscle was significantly increased in patients with IM (table 1). All patients had a deltoid fascia thickness above 2 SD. The fascii of the vastus lateralis muscle were not thickened in IM patients.
Conclusions This study reveals evidence of fascia thickening in the deltoid muscle of IM patients, indicative of a concomitant fasciitis in this disease. Further studies including more muscles and comparison with muscle biopsy will elucidate the extent of involvement of the muscle fascia in myositis.
Disclosure of Interest None Declared