Chronic myopathy associated with coxsackievirus type A9. A combined electron microscopical and viral isolation study.

Virus-like crystalline structures in human skeletal muscles have been observed by many electron microspists, but no viruses have been isolated and identified in such cases. An 11-year-old girl who had had muscular weakness and physical retardation since early infancy died of pneumonia due to atrophy of diaphragmatic and intercostal muscles. Electron microscopy of these muscles revealed a heavy infiltration of picornavirus-like particles that measured 19 to 23 nm in diameter. Subsequent inoculation of primary human-amnion cells with a sonic-treated suspension of the patient's diaphragmatic muscle induced an enterovirus-like cytopathic effect. The isolate was identified with use of Lim-Benyesh--Meinick enterovirus typing serum pools as coxsackievirus Type A-9. This viral isolation supports the belief that the organized electron-dense particles in human muscle are indeed virions.