Histopathology of erythromelalgia in thrombocythaemia.

Erythromelalgia always appears to be an expression of thrombocythaemia which may be provoked by intravascular platelet aggregation, because it is relieved by agents interfering with platelet prostaglandin synthesis. Biopsies were taken from affected areas 1-3 weeks after discontinuation of aspirin. At that time arteriolar changes were present: the endothelial cells were often swollen with large nuclei. Narrowing of the lumen occurred by proliferation of smooth muscle cells with vacuolisation and swelling of the cytoplasm and deposition of intercellular material. The internal elastic lamina appeared to be split between the proliferated cells. This gave rise to the appearances of fibromuscular intimal arteriolar proliferation which were often occluded by thrombi of differing age. Ultimately the arterioles become completely fibrosed. These vascular changes are restricted to arterioles, are partly reversible with aspirin treatment and seem to be a characteristic of erythromelalgia.