Valproic acid (VPA) is one of first-line traditional antiseizure drugs used for a variety of clinical conditions. Antiepileptic drugs most frequently associated with DRESS are phenytoin, phenobarbital, and carbamazepine.

Here, we present a case of DRESS induced by valproic acid and confirmed by patch test.

A 55-year-old man was treated with ceftriaxone, vancomycine and valproate for brain abscess. Three weeks later, the patient suffered from erythematous maculopapular eruptions without mucous membrane involving a large area of his face, back, bilateral shoulders and both lower limbs. Laboratory investigations revealed leukocytosis (15,6×109/L) with atypical lymphocytosis, elevated levels of transaminases and gamma-glutamyl transpeptidase. Viral serology including hepatitis B and C, cytomegalovirus, Epstein–Barr virus, parvovirus B19 and human herpes virus 6 were negative. In our case, definitive features of DRESS were present (score of 6 on RegiSCAR). DRESS-induced by valproic acid was suspected, antieepileptic drug was withdrawawn and corticosteroid therapy was initiated. Patch tests for valproic acid performed 4 months after complete recovery induced a strongly positive skin reaction in 48 and 72hours.

It is well known that aromatic antiepileptic drugs such as carbamazepine, phenobarbital and phyentoine are common causative drugs of DRESS syndrome. However, only a small number of case reports have described valproic acid-induced DRESS syndrome. Aromatic antiepileptic drugs may induce DRESS in patients with a defect in the epoxide hydrolase in patients with a history of reaction to the drug. The diagnosis of valproic acid-induced DRESS may be difficult. Therefore, Patch testing can be helpful in confirming the imputability.

Clinicians should be aware of the possibility of DRESS with valproic acid. The rule out of other possible diagnoses should not delay the interruption of the suspected drug and the beginning of supportive therapies.