ANTIMYOSIN SCINTIGRAPHY IN PATIENTS WITH ACQUIRED AND HEREDITARY MUSCULAR DISORDERS

Scintigraphy with indium-lll labelled antimyosin has an established ro le in the evaluation of cardiac muscle damage. This antibody has been shown to cross-react with myosin in skeletal muscle. We therefore stud ied the usefulness of this method for the detection of skeletal muscle lesions in rhabdomyolysis, myositis and hereditary muscular dystrophi es. All nine patients with rhabdomyolysis had focal uptake of antimyos in antibody which correlated with the clinical findings of soft tissue damage. However, a number of symptomless lesions were also detected b y immunoscintigraphy. In rhabdomyolysis the target to non-target uptak e ratios varied from 1.3 to 7.6. Diffuse uptake of antibody in skeleta l muscle was observed in all three patients with polymyositis-dermatom yositis and in 12 out of 13 patients with muscular dystrophies. In myo sitis the intensity of antibody accumulation correlated reasonably wel l with the magnitude of oedema detected by magnetic resonance imaging (MRI). Most patients with Becker type or non-X-chromosomal muscular dy strophies showed slight or moderate uptake of antibody, mainly in the lower extremities. In these patients more antibody accumulated in the calves than in the thighs, whereas the findings on MRI were more promi nent in the thighs than in the calves, presumably because of the bette r preserved muscle bulk in the calves. We conclude that antimyosin sci ntigraphy can be used for the detection of muscle lesions not only in acquired muscle diseases but also in hereditary muscular disorders, an d that immunoscintigraphy provides information on muscle disease activ ity not obtainable with MRI.