Pruritus in polycythemia vera: treatment with aspirin and possibility of platelet involvement.

The characteristic temperature-dependent pruritus in polycythemia vera (PV) is described. The triggering factor seems to be a sudden decrease in skin temperature, e.g. after a hot bath or shower. The sudden onset and limited duration of the pruritus might suggest an activation or release of some humoral factor(s). In a controlled study we showed that aspirin alleviates this particular pruritus. Therefore, the possibility of prostaglandin and platelet involvement was considered. It was found that substances such as PGE2 and serotonin, produced and released by platelets, could elicit pruritus in healthy volunteers when injected intradermally and that PGE2 enhanced the cutaneous responses to serotonin. Studies of platelet aggregation did not reveal any abnormalitites in the PV patients but ADP was shown to sensitize platelets to adrenaline-induced aggregation in vitro. Although not proven the following hypothesis is suggested: a combination of ADP, emerging from erythrocytes, and catecholamines released from adrenergic vasoconstrictor nerves when the skin is cooled down, might stimulate platelets to aggregation in skin vessels and to production and release of pruritogenic factors.