INTRODUCTION: Myofibrillar myopathies (MFMs) are hereditary muscle diseases characterized by distinctive histopathology of myofibrillar disintegration and abnormal protein aggregation. Seven genes: DES, CRYAB, MYOT, FLNC, LDB3, BAG3, PLEC encoding proteins associated with Z disc are considered responsible for MFMs. However in about half of patients, the gene defect is still unknown. AIM(S): The aim of this study was to describe the clinical and histopathological features of genetically confirmed MFM. METHOD(S): 13 patients from 4 families with MFM were systematically identified and clinically studied. The families were not known to be related. In all suspected MFM patients (one proband from each family) disintegration of myofibrils and accumulation of degradation products into inclusions containing desmin were detected in muscle biopsy. However differentiation between MFM subtypes on the basis of clinical/ pathological phenotype alone was impossible. Therefore, subtype identification was performed using molecular studies. RESULTS: All patients presented with progressive muscle weakness with distal-proximal distribution in the lower limbs. CK was normal or slightly elevated. Finally three mutations were identified: two in DES: (Q348P) and (A357_E359del) and one in CRYAB (D109A). In two families with desminopathy caused by A357_E359del mutation cardiac arrhythmias was observed (paternal uncle with similar symptoms died due to cardiac arrhythmia). Dilated cardiomyopathy was confirmed by echocardiography in family with CRYAB D109A. In this family respiratory insufficiency as well as early cataract were diagnosed. CONCLUSIONS: Molecular identification of MFM is crucial for final diagnosis. The awareness of MFM type could be life-saving by means of appropriate treatment such as 1) inserting of a pacemaker in case of significant heart conduction defects and arrhythmia or 2) initiation of noninvasive ventilation in case of chronic respiratory failure.
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