Early-Onset Drug Hypersensitivity Syndrome in a Man With Pneumonia Due to Pre-sensitization to Olanzapine

Drug hypersensitivity syndrome (DHS) generally starts two weeks to two months after administration of certain drugs. Olanzapine has been reported to cause drug reaction with eosinophilia and systemic symptoms (DRESS), but rarely causes drug-induced hypersensitivity syndrome (DIHS). A 49-year-old schizophrenic man was hospitalized for pneumonia and developed DIHS/DRESS 10 days after starting olanzapine. Although reactivation of human herpesvirus 6, which is one of the diagnostic criteria for DIHS, was not confirmed, the diagnostic criteria for DRESS were met. The patient may have developed early-onset DIHS/DRESS because he was sensitized to olanzapine prior to hospitalization.