Muscle involvement in rheumatoid arthritis: An ultrastructural study

An electron microscopic investigation has been carried out on muscle biopti c samples from patients affected by rheumatoid arthritis (RA). This study w as undertaken to seek further ultrastructural alterations affecting striate d muscles in RA pathology. Bioptic samples were collected on a total of 30 surgical interventions of hip (10), knee (8), and foot (12). This yielded t hree muscle types: gluteus maximus, vastus lateralis, and extensor digitoru m communis. Muscle samples from 12 patients with no RA stigmata, selected t o match RA patients by age and gender, constituted the control group. Tissu e samples were prepared both for conventional histochemical methods and acc ording to conventional electron microscopic procedures, including morphomet ric analysis. Although to a different extent in each sample, in muscles fro m RA vs. controls the authors observed the simultaneous presence of discret e muscular alterations such as wider separation of myofibrils, myelin figur es, dilated sarcotubular system, pleomorphic mitochondria, myofibril flakin g, and lipofuscin deposition in the subsarcolemmal region. In addition to a progressive atrophy, the above findings are suggestive of rheumatoid myosi tis and lend further support to the still poorly documented presence of an idiopathic inflammatory myopathy and inclusion body myositis associated wit h RA.