Viruslike particles in muscle from a patient with amyotrophic lateral sclerosis.

An electron microscopic study of muscle and central nervous tissue from a case of amyotrophic lateral sclerosis showed crystalline arrays of 20 to 24 nm viruslike particles in muscle. The particles were located between the myofibrils, adjacent to the Z bands, and near the perinuclear region, but were never seen within the nucleus. Cell cultures from the same muscle specimens showed no such particles. Central nervous system tissues and cultures also failed to show viruslike particles. The cultures were negative by the indirect fluorescent antibody technique with serums from patients with amyotrophic lateral sclerosis. The nature of these particles or their relationship to amyotrophic lateral sclerosis is unknown.