Severe scrub typhus confirmed early via immunohistochemical staining.

We describe a case of interstitial pneumonia that was confirmed as scrub typhus by immunohistochemical (IHC) staining of an eschar. When a patient presents with interstitial pneumonia accompanied by generalized lymphadenopathy on the thoracic CT scan, clinicians should suspect scrub typhus, especially when the patient has a history of travel to a scrub typhus-endemic area. IHC staining on an eschar revealed invasion by Orientia tsutsugamushi coccobacilli of the patient's sweat ducts and glands as well as vascular endothelium. IHC staining of an eschar could be used as an early-confirmation diagnostic method to establish scrub typhus.