Abstract
Japanese spotted fever (JSF) is an uncommon but potentially fatal infection transmitted by tick bites. We herein report a fulminant case of JSF infection that occurred in an immunocompetent adult that was complicated by disseminated intravascular coagulation and hemophagocytic lymphohistiocytosis (HLH). We discuss the difficulty in making the diagnosis and identifying the complication of HLH in our patient. HLH is a rare complication of rickettsiosis, and this is the first reported case in English of JSF complicated by HLH in an immunocompetent adult. Secondary HLH caused by rickettsiosis requires a different treatment from primary HLH. Rickettsiosis must therefore be considered in patients with HLH.