[Drug hypersensitivity: When systemic symptoms and pustules converge]

Overlap (SCARs) severe cutaneous adverse drug reactions, are defined as cases that fulfill diagnostic criterio for at least two of these drug-associated reactions, according to scoring systems. We present a case of an overlapping SCAR.

A 53-year-old female was diagnosed with diabetes and was being treated with metformin and linagliptin, and with high blood pressure with nifedipine. Secondary to an isolated seizure, she was treated with phenytoin, 5 weeks later, she presented with erythema in the chest region accompanied by pruritus that spread to the abdomen. Treatment was initiated with antihistamines, with poor improvement, progressing to generalized erythema and fever. Upon admission, she presented with generalized polymorphic skin lesions of a maculopapular rash and bullous lesions on the forearms, as well as pustular lesions on the face. Laboratory findings: Leukocytosis with neutrophilia (67%), eosinophilia =3,880/mm3, and acute kidney injury. Biopsy: Chronic interface dermatitis, superficial perivasculitis, and eosinophilia. According to RegiSCAR scoring system with 4 points and the EuroSCAR score with 6 points, both considered probable The patient began steroid therapy with methylprednisolone at 1.5 mg/kg for 3 days, followed by reduced doses of prednisone.

The patient presented a severe cutaneous adverse reaction 5 weeks after starting phenytoin, which showed overlap according to the scales. Secondary to the ambiguities among SCARs, confirmed cases of overlap are rare. In the acute stage of the disease, early identification of SCARs can be difficult due to overlapping features.