RESUMO
Primary adhalin (or alpha-sarcoglycan) deficiency due to a defect of the adhalin gene localized on chromosome 17q21 causes an autosomal recessive myopathy. We evaluated 20 patients from 15 families (12 from Europe and three from North Africa) with a primary adhalin deficiency with two objectives: characterization of the clinical phenotype and analysis of the correlation with the level of adhalin expression and the type of gene mutation. Age at onset and severity of the myopathy were heterogeneous: six patients were wheel-chair bound before 15 years of age, whereas five other patients had mild disease with preserved ambulation in adulthood. The clinical pattern was similar in all the patients with symmetric characteristic involvement of trunk and limb muscles, calf hypertrophy, and absence of cardiac dysfunction. Immunofluorescence and immunoblot studies of muscle biopsy specimens showed a large variation in the expression of adhalin. The degree of adhalin deficiency was fairly correlated with the clinical severity. There were 15 different mutations (10 missense, five null). Double null mutations (three patients) were associated with severe myopathy, but in the other cases (null/missense and double missense) there was a large variation in the severity of the disease.
Assuntos
Proteínas do Citoesqueleto/deficiência , Proteínas do Citoesqueleto/genética , Genes Recessivos , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Distrofias Musculares/genética , Distrofias Musculares/fisiopatologia , Adolescente , Adulto , Criança , Pré-Escolar , Proteínas do Citoesqueleto/metabolismo , Progressão da Doença , Feminino , Genes , Humanos , Immunoblotting , Imuno-Histoquímica , Masculino , Glicoproteínas de Membrana/metabolismo , Músculos/patologia , Músculos/fisiopatologia , Distrofias Musculares/patologia , Mutação , SarcoglicanasRESUMO
The prevalence of cardiac complications of dermatomyositis and polymyositis is generally underestimated. The authors report the case of heart block as the presenting symptom of the disease, situated in the atrioventricular node. Initially paroxysmal, it eventually became permanent. It was associated with atrial (fibrillation and flutter) and ventricular hyperexcitability (ventricular tachycardia in runs). Myocardial biopsy provided histological proof of the cardiac disease and the definitive link between the nodal conduction defect and the polymyositis.