PHENYTOIN HYPERSENSITIVITY SYNDROME WITH POSITIVE PATCH TEST - A POSSIBLE CROSS-REACTIVITY WITH AMITRIPTYLINE

A 34-year-old woman, after 2 weeks of treatment with phenytoin and ami triptyline, developed fever and cutaneous lesions consisting of a gene ralized maculopapular rash and eosinophilia. Her biochemical data show ed abnormal liver functions with increased levels of SGOT; SGPT; LDH, gamma-glutamyl transpeptidase and alkaline phosphatase. The skin biops y pattern was compatible with phenytoin drug eruption of the erythema- multiforme-like type (lymphocytic exocytosis, isolated dyskeratotic ce lls, vacuolation of basal cells and incontinence of pigment). The patc h tests were positive with phenytoin (patch test biopsy showed a typic al eczematous pattern). The patch test with amitriptyline was negative . An oral challenge with amitriptyline showed an erythematous maculopa pular rash. The challenge with phenytoin was not carried out because t he previously abnormal liver function tests contraindicated the challe nge. Although there are a few cases reported, the patch tests could be useful for diagnosing phenytoin allergy. Cross-reactivity between phe nytoin and amitriptyline is possible.