PONM04 Myofibrillar myopathy caused by a mutation in the desmin gene: expanding the phenotype

Background Myofibrillar myopathy (MFM) is a group of morphologically distinct muscle disorders, with genetic and phenotypic variability. When a mutation in the desmin gene is found, it is termed a desminopathy. These patients often present with distal muscle weakness in the lower limbs spreading to involve proximal muscle groups. Cardiomyopathy may be a prominent finding. To our knowledge, vocal cord palsy has not been described in this condition. Case Description A 48-year-old man presented at the age of 39 years with progressive, predominantly distal, lower limb weakness and bilateral ankle contractures. He developed a cardiomyopathy and arrhythmias. Three men in his family were similarly affected and passed away in their fifties. Recently, he presented with hoarseness with bilateral vocal cord palsies confirmed on laryngoscopy. Results of Investigations Limb EMG confirmed an active myopathic process. The muscle biopsy showed fibre size variation and rimmed vacuoles. Genetic testing identified a heterozygous mutation in the desmin gene (c.1346A>C (p.Lys449Thr)). Discussion Vocal cord palsy has been described in the autosomal dominant myopathy: vocal cord and pharyngeal weakness with distal myopathy (VCPDM). However, it has not been described in association with a desminopathy and therefore expands the phenotype of this myofibrillar myopathy subgroup.