More Than Skin Deep – Fibrosis of Muscle in Scleroderma is Associated With Increased Mortality

Overlap syndromes in inflammatory myopathy can be challenging to manage, and may be associated with poor outcomes. One of my myositis colleagues, Dr. Julie Paik, is a frontrunner in the field of scleroderma and myositis research (Abstract #1894). Dr. Paik has noted that skeletal myopathy in systemic sclerosis (SSc) is associated with poor outcomes. The presentation of myopathy in such patients varies, and phenotypes may correlate with muscle biopsy histology.

Dr. Paik undertook a retrospective, cross-sectional study that included SSc patients with muscle weakness who had muscle biopsies available for review. Features on biopsy, such as inflammation, necrosis, and fibrosis, were analyzed. The term ]"fibrosing myopathy was used to describe histology that consisted of predominant fibrosis or necrosis with very little inflammation. Clinical data corresponding to patient phenotype, such as SSc subtype, disease duration, EMG findings, CK levels, and autoantibody profile, were collected.

Of 47 biopsies analyzed, 8 had fibrosing myopathy. These patients had a statistically significantly higher mortality rate compared to those with inflammatory myopathy on muscle biopsy. They were also more likely to have the diffuse SSc phenotype, be African American, and have a shorter disease duration since first non-Raynaud's symptoms as well as a lower FVC, although the above findings did not reach statistical significance. There was also a trend towards lower CK values and higher rates of detection of Scl-70 antibodies. They had irritable myopathy on EMG.

These data suggest that SSc patients with muscle weakness and fibrosis on muscle biopsy have a higher risk of mortality than those with inflammatory myopathy findings. It is interesting to note that these patients have lower CK despite findings of irritable myopathy on EMG. Given that SSc can have high mortality rates depending on organ involvement, it appears as though certain subtypes of muscle involvement can increase mortality rates further. The question is whether or not we should be screening for muscle disease in these patients at diagnosis; however, most patients will present with weakness as a predominant symptom.

More reports from ACR 2016