Phenytoin hypersensitivity syndrome

To the Editor,

The phenytoin hypersensitivity syndrome consists of an erythematous cutaneous eruption which usually begins 1 to 3 weeks after phenytoin is started and eventually turns purpuric accompanied by fever, facial oedema, tender generalised lymphadenohpathy, leukocytosis with variably associated hepatitis, nephritis, and pneumonitis.[1],[2] It probably results from the deficiency of the enzyme epbxide hydrolase which detoxifies the toxic intermediates generated by the metabolism of the aromatic anticonvulsants.[1]

A 13-year-old-boy presented to our Skin and STD OPD with high grade fever, dyspnoea, maculo-papular skin rash, conjuctival congestion, cheititis and facial oedema. He was an epileptic and was on phenytoin sodium for 10 days. The skin rash which involved the trunk, face and extremities including palms and soles soon became purpuric. Lips were swollen and showed erosions, oozing and crusting. Erosions were seen in oral mucous membrane too. There was tender cervical and inguinal lymphadenopathy. There was neither hepatosplenomegaly nor jaundice. There was no neck rigidity. Leukocyte count was 12000/ cu mm with lymphocytosis but without atypical cells. Serum protein, blood urea, s creatinine and routine urine examination were within normal limits and remained so during follow up. Chest X-ray showed a zone of pneumonitis in left upper zone. The boy responded excellently to the immediate stoppage of phenytoin and institution of short course of systemic glucocorticoids patient was switched over to sodium valproate. A single dose of phenytoin sodium after 3 weeks caused manifestation of similar clinical features but in a milder form.

Early recognition of this hypersensitivity reaction is required to prevent the development of toxic epdermal necrolysis, fatal hepatitis and nephritis.