Acta Dermato-Venereologica 99-7CompleteContent

SHORT COMMUNICATION S-Carboxymethyl-L-cysteine-induced Fixed Drug Eruption Hidetsugu FUKUDA and Misaki TAKAHASHI Department of Dermatology, Toho University Ohashi Medical Center, 2-22-36, Ohashi, Meguro-ku, Tokyo 153-8515, Japan. E-mail: h-fukuda@ med.toho-u.ac.jp Accepted Apr 2, 2019; E-published Apr 2, 2019 S-carboxymethyl-L-cysteine (carbocisteine, SCMC) is a mucoregulating drug with a normalizing effect on airway mucus and a repairing effect on mucosa. The drug is used in a wide range of age groups, from infants to elderly patients. SCMC has chronopharmacological characteristics, i.e. its metabolic pathway and metabolites vary according to the time of day when the drug is orally ingested (1, 2). Thiodiglycolic acid (TDA), a metabolite produced during the night, has been assumed to be a component responsible for fixed drug eruption (FDE) associated with SCMC (3). This report presents a case of SCMC-induced FDE in which an oral challenge test induced a skin eruption following oral administration of SCMC in the evening only for 2 days. CASE REPORT A 4-year-old boy presented with an erythema, which had developed on the left forearm after treatment with oral SCMC (500 mg every 689 12 h), tipepidine hibenzate (30 mg every 12 h) and other drugs was initiated 7 months previously. The patient had cold symptoms 1 month before he visited another hospital. SCMC and tipepidine hibenzate were administered orally for several days before the erythema was noted. Subsequently, a brown pigmented macule remained, and the patient visited our department for examination. On initial assessment, a relatively well-defined brown spot, 21×15 mm in size, was noted on the flexor side of the left forearm (Fig. 1a). The patient did not report any symptoms such as itching. His family history and past medical history were non-contributory. SCMC- or tipepidine hibenzate-induced FDE was suspected based on the above clinical findings. To identify the responsible agent, a patch test (PT) and oral challenge testing were performed. Four weeks after the first visit to our department, PT was per- formed. In the PT, SCMC 20% petrolatum (pet), TDA 10% pet, and TDA 20% pet were applied on the affected area on the left forearm. The SCMC 20% pet was negative, whereas TDA 10% pet and TDA 20% pet were (?+) at 72 h and (+) on day 5 according to the International Contact Dermatitis Research Group (ICDRG) criteria (Fig. 1b, 1c). ((ICDRG criteria) −: no reaction < negative reaction >, ?+: faint erythema only < doubtful reaction >, +: ery thema, inﬁltration, possibly papules < weak positive reaction >, ++: erythema, inﬁltration, papules, vesicles < strong positive Fig. 1. (a) A relatively well-defined brown spot was noted on the flexor side of the left forearm during the patient’s first visit to our hospital. (b) The thiodiglycolic acid (TDA)10% pet and TDA 20% pet were (?+) according to the International Contact Dermatitis Research Group (ICDRG) criteria after 72 h from the patch application. (c) The TDA 10% pet and TDA 20% pet were (+) according to the ICDRG criteria from 5 days after the patch application. (d) An erythema developed on the brown spot during the night when a single dose of S-carboxymethyl-L-cysteine (carbocisteine, SCMC) was orally ingested in the evening for 2 days. This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica. doi: 10.2340/00015555-3193 Acta Derm Venereol 2019; 99: 689–690

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