• Absence of thick filaments from A bands in 30% of myofibers, which gave apparently normal histochemical reactions for myosin adenosine triphosphatase, was seen in a case of periarteritis nodosa. The pathogenesis of the condition remains uncertain, but immunologic, toxic, or viral causation may be involved. This pathological change seems to be reversible with a good prognosis.
Itzhak Halperin, Isaac Kobrin, Michael Ilsar, Gil Lugassy, Rena Yarom. Thick-Filament Degeneration Associated With Periarteritis Nodosa. Arch Neurol. 1982;39(11):730–732. doi:10.1001/archneur.1982.00510230056018