Core/targetoid fibres and multiple cytoplasmic bodies in organophosphate neuropathy.

From correlated histochemical and ultrastructural investigations of biopsy specimens of a rare case with delayed-onset neuropathy due to organophosphate (Dipterex) intoxication, several pathological characteristics were recognized in the muscle fibres. Most striking was concurrence of core/targetoids and multiple cytoplasmic bodies in the same fibres. Foci of markedly reduced or absent oxidative enzyme activity were revealed in 71.6% of type I fibres and in 3.4% of type II fibres. Most of those foci were two-zoned core/targetoids. Cytoplasmic bodies were also revealed selectively in type I fibres contrary to the previous reports. Targets, targetoids, cores and multicores were suggested to be strongly related to each other pathogenetically and to be due to the disturbance of some neurotrophic influences. In the biopsy specimen taken 220 days after exposure to the drug, numerous sarcoplasmic masses were revealed, and they were very likely to represent special forms of regeneration.