A skin condition that occurs frequently in people with HIV in sub-Saharan Africa is caused by insect bites rather than an infectious agent, and is a strong indicator of HIV infection, according to researchers from the United States and Uganda. The findings were reported on February 11th at the Eleventh Conference on Retroviruses and Opportunistic Infections in San Francisco.
In a study carried out in Uganda, researchers investigated the causes of skin eruptions that harden into scarring nodules called prurigo, or pruritic papular eruption. The condition is widely observed in people with HIV in sub-Saharan Africa, but rarely seen in North America or Europe.
The cross-sectional study investigated skin eruptions in 132 individuals receiving treatment at two centres, one a village clinic and the other a clinical research centre at Mulago Hospital. Individuals receiving care at both centres had advanced HIV disease; the average CD4 cell count of participants in the study was 124 cells/mm3 at the village clinic and 74 cells/mm3 at Mulago Hospital.
The skin eruptions were biopsied and examined to determine the cause of the eruption. In 84% of cases, the morphology of the eruption was strongly suggestive of an insect bite, with insect antigens often detectable. 20% had a severe rash, with a degree of eisonophil count elevation strongly correlated with the severity of the rash. No case of folliculitis, the most common skin eruption in patients in temperate climates, was seen.
The researchers suggested that the altered reaction to insect bites seen in people with HIV is a consequence of a falling CD4 cell count, and that the reaction is analogous to the increased intolerance to some medications seen in patients with lower CD4 cell counts.
Interestingly, researchers learnt from patients that the skin eruptions invariably started in the same way, with a small red bite mark that rapidly became inflamed as a result of intolerable itching. However, no one had thought to ask the patients about the potential pathogenesis of this widespread condition.
Two types of intervention will now be investigated. One is the use of insecticides to reduce insect biting and hence prurigo, the other is observation of patients receiving antiretroviral therapy to determine if the condition becomes less frequent with immune reconstitution. Anecdotal evidence suggests that antiretroviral therapy does control prurigo, and Kevin De Cock of the Centers for Disease Control suggested that prurigo should be added to the list of indicator conditions for commencing antiretroviral therapy, since it is indicative of immune suppression.
Resnack J et al. The pruritic papular eruption of HIV in Uganda is a reaction to insect bites. Eleventh Conference on Retroviruses and Opportunistic Infections, San Francisco, abstract 149, 2003.