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A 22 year old woman with a history of congenital cataracts and surgically corrected strabismus in October 2020, presented for evaluation of progressive distal lower greater than upper extremity weakness over the last 5 years. She additionally reported dysphagia with solids, weight loss, dyspnea on exertion, orthostasis, ptosis, and hoarseness of her voice. There was no family history of neuromuscular disorders. Neurologic exam was significant for mild weakness of foot dorsiflexion, trace tendon reflexes throughout, and slow relaxation of handgrip but no percussion-induced myotonia of thenar or wrist extensor muscles. Ptosis and ophthalmoparesis were not observed. Creatine kinase was normal. Nerve conduction studies were normal. Needle electromyography showed diffuse myotonic discharges and early recruitment of small, polyphasic motor unit potentials in proximal and distal muscles. Fibrillation potentials were absent. Repetitive nerve stimulation showed no decrement. Genetic testing for myotonic dystrophy types 1 and 2, SCN4A- and CLCN1-channelopathies, Pompe disease, and congenital myasthenic syndromes were negative. Whole exome sequencing disclosed a pathogenic p.Arg369Gln variant in dynamin 2 gene (DNM2). Muscle biopsy was not performed. DNM2- myopathy can present with slowly progressive distal weakness, early-onset cataracts, and electrical myotonia, mimicking myotonic dystrophy. History of ophthalmoparesis is a helpful diagnostic clue.