Sir,

Drug-induced baboon syndrome, recently renamed symmetrical drug-related intertriginous and flexural exanthema (SDRIFE), is a flexural toxidermia characterized by a symmetrical erythematous and intertriginous rash. The major drugs causing SDRIFE are beta-lactam antibiotics, such as amoxicillin and ampicillin [1,2]. Herein, we report the case of a 21-year-old female who was diagnosed with SDRIFE due to oral metronidazole.

A 21-year-old female, diabetic type 1 on insulin, had been suffering from a perianal abscess for four days and was being treated with oral metronidazole by self-medication. Twelve hours after administration, she presented with sharply demarcated V-shaped macular erythematous patches on the axillary region, elbow folds, gluteal area, thighs, and groins (Figs. 1a – 1c). Systemic examination was normal, except for the perianal abscess. Laboratory investigations showed normocytic anemia and slight C-reactive protein elevation with no eosinophilia. The diagnosis of drug-induced baboon syndrome was, therefore, established on the basis of the chronological and semiological data. A biopsy and patch test were not taken because the patient did not give consent. The treatment was based on antihistamines and topical corticoids with good clinical improvement and desquamation after one week.

Figure 1: Erythematous lesions on the inner thighs (a), popliteal folds (b), and elbow folds (c).

The term baboon syndrome (BS) was introduced in 1984 as a description of a specific skin eruption after systemic exposure to contact or systemic allergens [3].

Drug-related baboon syndrome is a clinical diagnosis constituted by five criteria: exposure to a systemic drug at the initial or repeated dose (excluding contact allergens); sharply delimited erythema of the gluteal/perianal area and/or V-shaped erythema of the inguinal/peri-genital area; involvement of at least one other intertriginous/flexural site; symmetry of affected areas; and the absence of systemic symptoms and signs such as pyrexia, eosinophilia, and cytopenia [4,5]. Our patient fulfilled all of the listed criteria of SDRIFE due to oral metronidazole.

BS may be caused by topical or systemic applied substances. The most common systemic drugs involved are beta-lactam antibiotics, mainly amoxicillin, mercury, nickel, pseudoephedrine, allopurinol, oxycodone, naproxen, heparin, oral neomycin, oral glucocorticoids, and many others [6]. Metronidazole, a nitroimidazole antibiotic used in the treatment of anaerobic bacterial infections, is generally well-tolerated, with the first case in the literature described in Turkey by Aysun Sikar at el. in 2014 [4]. To our knowledge, our patient was the second case in the literature to develop SDRIFE due to oral metronidazole.

Treatment is based on the discontinuation of the drug, antihistamine, local corticosteroid therapy, and in some cases, systemic corticosteroid therapy. The prognosis is generally good; however, a new oral provocation is likely to recur [7].

The diagnosis of SDRIFE should, therefore, be suspected in the presence of any pruritic and symmetrical intertriginous eruption involving drugs with no systemic involvement, whatever the molecule.

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