Two cases of eruptive pseudoangiomatosis induced by mosquito bites

Eruptive pseudoangiomatosis is a skin eruption characterized by millet-sized erythema with an anemic halo appearing on exposed body areas. Insect bites, particularly mosquito bites, have been reported as one of the causes of eruptive pseudoangiomatosis. We experienced two cases of eruptive pseudoangiomatosis and the eruption was seen on the face and upper extremities of two women aged 48 and 77 years old. The two cases consented to be experimentally bitten by Culex pipiens mosquitoes and Aedes albopictus to determine if eruptive pseudoangiomatosis could be experimentally elicited by these mosquitoes. Our results showed that several minutes after a C. pipiens mosquito bite, an erythematous spot appeared on the bite site, followed by the formation of an anemic halo surrounding the erythema in 30 min; a successful reproduction of eruptive pseudoangiomatosis. The erythema lasted for more than a week and was not accompanied by any pruritus. With A. albopictus, we were able to reproduce a milder eruptive pseudoangiomatosis eruption: in case 1, a smaller erythematous spot with an ill-defined halo which disappeared within 1 week; and in case 2, an immediate response consisting of a wheal and erythema but not eruptive pseudoangiomatosis. We demonstrated that eruptive pseudoangiomatosis was the response manifested in individuals who normally did not demonstrate any immediate or delayed reaction to insect bites; and the typical eruptive pseudoangiomatosis eruption was elicited by C. pipiens mosquito bites. However, the mechanism resulting in the manifestation of eruptive pseudoangiomatosis is still unknown.