DRESS syndrome: A case of cross-reactivity with lacosamide?

A 42-year-old patient with epilepsy was admitted to the hospital for fever and generalized skin rash. He has known allergy to phenytoin. Valproate was started in 2012, but failed to control his seizure despite gradual increase in dosage. Phenobarbitone was added 16 days before admission and was stopped on admission. He was treated with beta-lactam antibiotics. The rash subsided gradually after the cessation of phenobarbitone. Lacosamide was subsequently added for seizure control. Unfortunately, he developed drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome soon after introduction of lacosamide that required the use of systemic steroid for acute hepatitis. A cross-reactivity with lacosamide was suspected in view of the rapid onset of DRESS syndrome after the initial rash resolution and soon after the introduction of lacosamide. We postulated that the rapid onset of DRESS syndrome may be related to the aromatic ring that is in common among phenytoin, phenobarbitone, and lacosamide.