Inclusion body myositis. Clinical, biological and ultrastructural study.

A 48-year-old patient presented for the past 4 years an amyotrophy of the quadriceps and moderate involvement of the truncal and pelvic girdle muscles. The CK level was elevated (10 times the normal rate) and the EMG revealed a fibrillation pattern on relaxation, myotonic bursts on needle insertion and reduced activity during contraction. The histological study of the muscle biopsy showed nuclear cytoplasmic inclusion bodies and pseudo-myelinic membranes. The case was classified in the inclusion body myositis group. Analysis of the other published cases underlines the variety of the clinical, biological and electromyographical aspects and abnormalities.