Abstract
Lichenoid drug eruption (LDE) is a rare form of delayed-type drug eruption. Among anti-tuberculosis (Tb) agents, cycloserine (CS) has been reported as a rare cause of LDE. Positive results on the lymphocyte transformation test (LTT) have not been reported in patients with LDE. In the present case, we performed LTT and a patch test, and successfully proved CS as the offending drug in this patient, who had been treated with multiple anti-Tb drugs. These observations suggest that CS should be considered a possible cause of LDE and that LTT can be an option for the diagnosis of LDE.