The heart of myofibrillary myopathy

Context: Myofibrillar myopathies (MFM) represent a heterogeneous group of disorders of skeletal and cardiac muscle caused by mutations in genes that encode proteins of sarcomere. Diagnosis is a challenge due to clinical and genetic variability. Case report: Woman, 36 years old, presenting stumbles and falls for 3 years evolving with proximal limb weakness. At age 30, she fainted and a cardiac pacemaker was implanted. Non-consanguineous parents. Neurological exam: proximal and distal weakness in lower limbs and distal atrophy; osteotendinous reflexes normal. Bilateral scapula alata. Exams: CPK = 457 U / l; EMG: myopathic pattern. Muscle MRI: diffuse and heterogeneous fatty degeneration, marked in sartorius, gracilis and semitedinous. Panel NGS myopathies: pathogenic variant, c.1175T> C, missense in heterozygosis in desmin gene. CONCLUSION: The diagnosis of MFM is based on the morphological findings of muscle biopsy with the presence of protein aggregates as a determining factor. Currently, genetic testing by NGS has facilitated early diagnosis allowing for a more appropriate clinical approach. The desmin gene was the first one described to be associated with this group of myopathies. It encodes the desmin protein, a member of the intermediate filament family present in cardiac and skeletal muscle. Several phenotypes are related to desmin gene: isolated dilated cardiomyopathy; scapuloperoneal weakness and distoproximal weakness with cardiac alterations. Desminopathy is a rare cause of cardiomyopathy and / or myopathy. The diagnosis should be thought in patient with muscle weakness and cardiac changes.