[Stevens-Johnson syndrome in a patient with positive lymphocyte transformation test].

Background: Stevens-Johnson syndrome is a severe drug reaction. Sulfonamides have been associated with drug reactions, complications, sequelae, even death.

Case report: A 40-year-old female patient with a medical history of endometriosis and recently diagnosed chronic inflammatory ulcerative colitis. She was treated at the Allergology service of the San Juan de Dios Hospital of the Costa Rican Social Security Fund, and after 20 days of treatment with sulfasalazine she had a severe drug reaction on the skin, compatible with Stevens-Johnson syndrome. The lymphocyte transformation test was positive, confirming sulfasalazine as the causative agent.

Conclusion: The lymphocyte transformation test is a useful method that can confirm the causative agent and prevent important complications in the future.