[Selenoprotein-related myopathy in a patient with old-age-onset type 2 respiratory failure: a case report].

A 71-year-old woman was admitted to our hospital with type2 respiratory failure. Her daily life activities had been normal, although she had noticed mild truncal weakness in her sixties. Her parents were consanguineous, and her sister had suffered similar symptoms. Although Pompe disease was suspected on the basis of the clinical course and CT findings of selective muscular atrophy in the paraspinal, thigh flexor and sartorius muscle, acid alpha-glucosidase activity was normal. The serum creatine kinase level was not elevated, and muscle biopsy showed no specific change. Genetic analysis revealed a novel homozygous variant c.227T>C (p.Phe76Ser) in the SELENON gene, and she was suspected to have selenoprotein-related myopathy, which is reported to develop in childhood. Selenoprotein-related myopathy should be considered as a differential diagnosis in aged patients presenting with respiratory failure of unknown origin.