A search for genetic influence in idiopathic inflammatory myopathy

33 patients with idiopathic inflammatory myopathies (polymyositis or dermatomyositis) and 45 of their first-degree relatives were investigated in a search for any influence of genetic factors in these diseases. None of the relatives had evidence of an inflammatory myopathy but 13 had some other autoimmune disease. Mean serum IgG levels were reduced and serum C3c concentration increased both in patients and relatives. Levels of IgM were reduced and C4 increased in some groups of patients. The incidence of autoantibodies was increased in the patient group, particularly in those with isolated dermatomyositis or other systemic features, but not in the relatives. HLA, blood group and other genetic markers showed no deviation from normal population frequencies. Evidence favouring a genetic influence on the etiology of idiopathic inflammatory myopathy is restricted to disturbance of levels of some Ig and complement components, and for these there may be other explanations.

[Pathogenesis of polymyositis (author's transl)]

There are few convincing arguments for a direct intervention of humoral immunity mediated by specific antibodies or circulating immune complexes. Arguments in favour of a cytotoxic reaction are stronger. The likelihood of an infectious origin is supported by the presence of cell inclusions resembling myxovirus or picorna virus of the coxsackie group, and toxoplasmas may also be involved. The high incidence of associated cancers has given rise to speculations on the relationship between the two diseases, such as: myotoxic substances secreted by malignant tumours, delayed hypersensitivity reaction to a common antigen, or different effects of a single hypothetic causal agent.

Parasitic myositis by Echinococcus alveolaris. Report of a family with myotonia congenita

Echinococcus alveolaris infections were found in 5 members of a family and at least 3 of them also suffered from myotonia congenita. A muslce biopsy, performed in 1 case because of a pathological EMG finding allowed a diagnosis of parastic myositis caused by E. alveolaris to be made. In a further case, X-rays demonstrated calcification of an Echinococcus cyst in the thigh. Since is it only on rare occasions that these parasites are found in muscle tissue, factors are then discussed which might in some way be responsible for this high rate of E. alveolaris lesions in the muscles of patients with myotonia congenita.

Inflammatory myopathy in scapulo-ilio-peroneal atrophy with cardiopathy. A study of two families

A syndrome of slowly progressive muscle weakness with scapulo-ilio-peroneal distribution and cardiopathy was identified in 26 members of two families. Inheritance was autosomal dominant. Onset of the disease was between 17 and 42 years. Cardiopathy did not antedate skeletal muscle disease and patients had no symptoms of cardiopathy until a late phase of the disease. Initial ECG changes were non-specific, disturbances of conduction and impulse formation developed subsequently. Skeletal muscle biopsies showed neurogenic and myopathic changes with inflammatory cell reaction and perivascular cuffing. The combination of myopathy with neurogenic-like changes is characteristic of many cases of SPA. The inflammatory cell reaction is considered as part of a secondary polymyositis which is at leart partly responsible for muscle pathology.

Myositis in father and daughter

The occurrence of myositis in a father and his daughter is reported. The daughter's illness resembled childhood dermatomyositis and progressed to systemic involvement and death less than four years from the onset of symptoms. In the case of the father the illness followed the course of adult polymyositis and there was little evidence of systemic involvement. The immunological and genetic significance of the two cases is discussed.