Ultrastructural changes in the rectal mucosa of patients with rheumatoid arthritis.

The rectal mucosa from patients with severe rheumatoid arthritis has been examined by electron microscopy. Initially the patients were biopsied for investigation into the diagnosis of amyloidosis or vasculitis, which proved to be negative. A range of ultrastructural abnormalities was found which included proliferation of the rough endoplasmic reticulum, mitochondrial inclusions, association of the mitochondria with cytoplasmic filaments, and marked increase in the number of iron containing siderosomes. Most of these abnormalities have already been reported in rheumatoid synovial tissue, and attention is drawn to the similarity in findings between these two sites.