Ultrastructural study of neuromuscular and vascular changes in connective-tissue diseases.

Ultrastructural changes of the neuromuscular and microvascular systems were investigated in muscle biopsies obtained from patients with rheumatoid arthritis, systemic lupus erythematosus, dermato- and polymyositis and progressive systemic sclerosis. Myofibrillar degeneration, Z-disc streaming, mitochondrial abnormalities, alteration of the T system and sarcoplasmic reticulum were the main ultrastructural alterations observed in biopsy material. At the same time, severe peripheral nerve-fibre lesions were also observed. Thickening of the basement membrane around capillaries was repeatedly demonstrated, above all in rheumatoid arthritis and progressive systemic sclerosis. Immunocomplexes around capillaries and small vessels as well as along the sarcolemmal basement membrane were also often demonstrated.