Delayed-type hypersensitivity reaction to ethambutol and isoniazid.

A 24-year-old woman had recently started antitubercular therapy with isoniazid, ethambutol and rifampicin. This therapy was discontinued 2 weeks later due to an itchy, desquamative, erythematous, papular rash, with painful crusts and excoriations, spreading from the face and hands to the rest of the body. 5 days after withdrawal of all drugs, widespread desquamation and exfoliation with predilection for the body folds and the peri-orbital and peri-oral regions occurred, with swelling of the eyelids and conjunctivitis. Topical fluticasone propionate and oral cetirizine ameliorated the skin condition. The diagnosis of toxicoderma was supported by histology of the skin and an eosinophilia (31%). After the dermatitis had subsided, patch tests were performed with ethambutol, isoniazid and rifampicin (crushed and moistened with water). These were negative at the 1st reading at D2, but positive for both ethambutol and isoniazid at D3, showing erythema and infiltration. Patch tests with ethambutol and isoniazid were negative at D2 and D3 in 10 healthy controls.