By Gary M. White, MD
Flexural drug eruption or baboon syndrome (aka symmetrical drug-related intertriginous and flexural exanthema) is an unusual type of hypersensitivity drug rash. This is in essence a drug reaction with a peculiar distribution. The triggering agent may be skin contact with an allergen (e.g., a mercury-containing ointment, ampicillin otic solution), oral administration of a drug (e.g., amoxicillin [IJD 1996;35;502] or penicillin), intravenous, e.g., IVIG [Dermatology 1999;199;258-260] or chemotherapy. One of my patients developed diffuse sterile pustules on the erythema 3 days into the eruption. Of note, acute generalized exanthematous pustulosis may show a predilection for the intertriginous areas of the axilla and groin. A patient with Parvo virus B19 infection had an eruption similar to baboon syndrome.
The patient develops a diffusely red buttocks reminiscent of a baboon. The axilla and flexural areas of the inner thighs may also be affected. Pustules and erosions may develop.
Four cases of a flexural erythematous eruption (buttocks as well) following autologous peripheral blood stem cell transplantation have been reported [BJD 2001;145;490]. All of these patients had received high-dose chemotherapy and it was postulated that their rash resulted from an interplay between high-dose chemotherapy, friction, heat, and eccrine gland secretions.
Patch testing may be positive. For example, a patient who developed baboon syndrome after oral administration of penicillin was patch test positive to penicillin. Interestingly, prick test at 20 minutes and RAST test (for IgE to penicillin) was negative. A penicillin ID test was positive at 24 hours.
The offending agent should be identified and avoided. Oral steroids can rapidly improve the condition.
Baboon syndrome in a young woman.
The above patient developed pustules near the end of the course.
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