Exaggerated Delayed Hypersensitivity to Mosquito Bites in Chronic Lymphocytic Leukemia.

I T IS THE PURPOSE of this report to describe the occurrence of unusual cutaneous hyper-reactivity phenomena in certain patients having chronic lymphocytic leukemia. These reactions are consistent with an exaggerated delayed hypersensitivity type of response to insect bites, inoculated mosquito antigen and to certain other delayed hypersensitivity antigens. The mosquito is an example of certain insects whose bites are capable of evoking both immediate and delayed hypersensitivity types of cutaneous response. 4 Exaggerated delayed response may occur after initial sensitization and it is occasionally seen in children, but repeated exposure to the antigen seems to moderate the response. Spontaneous development of exaggerated delayed hypersensitivity to the mosquito is exceedingly rare in individuals past middle age. However, out of 97 cases of chronic lymphocytic leukemia that were seen between 1950 and 1963 at Strong Memorial Hospital, there were 8 individuals who were found to have severe troublesome local reactions to insect bites, usually mosquito. Such reactions display features consistent both with delayed cutaneous hypersensitivity and with leukemia cutis. The enhanced delayed hypersensitivity has led to further evaluation of the immunologic competency of these individuals.