A case of symmetrical drug-related intertriginous and flexural exanthema induced by acetaminophen Dear Editor, A 53-year-old man was treated with radiation therapy for prostate cancer. After radiation therapy, acute prostatitis developed.Cefcapene pivoxil and acetaminophen were administrated. One day after commencement of the two drugs, he noticed a sharply defined, symmetrical erythema on both legs, axillae, and buttocks without systemic symptoms (Fig. 1a,b). No mucosal lesions were seen. Laboratory tests revealed mild leukocytosis (9600/lL) and an increased level of C-reactive protein (8.84 mg/dL). The skin biopsy specimen from the cutaneous lesions on the buttocks showed small subcorneal neutrophilic pustules, numerous lymphocytes, and some eosinophilic infiltrates around upper dermal small vessels (Fig. 1c). After discontinuing cefcapene pivoxil and acetaminophen, oral prednisolone at 20 mg daily was administrated, and the erythema disappeared without pigmentation. Patch tests were negative. The lymphocyte transformation test for acetaminophen was positive at 140 cpm and the stimulation index (S.I.) was 218% (control was 64 cpm and the normal limit of S.I. is <180%). Oral provocation testing with acetaminophen resulted in an identical flexural rash on the right leg that appeared a few hours after provocation. A diagnosis of SDRIFE induced by acetaminophen was made based on the above findings.The baboon syndrome is a particular form of systemic contact dermatitis caused by systemic exposure to mercury, nickel, or other agents. 1 Drug-related baboon syndrome is also known as SDRIFE. The proposed criteria are: (i) exposure to a systemically administered drug (classical contact allergens have to be excluded); (ii) sharply demarcated erythema of the gluteal/perianal area and/or V-shaped erythema affecting the inguinal/perigenital area; (iii) involvement of at least one other intertriginous/flexural fold; (iv) symmetry of eruption; and (v) absence of systemic symptoms and signs. 2 Although our patient met all of these criteria, he did not have the characteristic inguinal erythema. The common histopathological finding is a superficial perivascular infiltrate of lymphocytes, sometimes with neutrophils and eosinophils. Other findings include epidermal spongiosis, subcorneal pustules, and vacuolar change in the basal layer. 3 SDRIFE is primarily a clinical diagnosis, and laboratory investigations and histopathological features are not strictly required for the diagnosis. The differential diagnosis of SDRIFE is fixed drug eruption and acute generalized exanthematous pustulosis (AGEP). Fixed drug eruption presents with a small number of violaceous plaques that leave postinflammatory hyperpigmentation. AGEP is characterized by (a) (b) (C) Figure 1. Sharply demarcated and symmetrical erythema on the (a) buttocks and (b) axillae. (c) Histopathological examination revealed a subcorneal neutrophilic pustule and perivascular infiltrate of lymphocytes and eosinophils in the upper dermis (hematoxylin-eosin stain, original magnif...