The Epidemiology and Clinical Features of Non-Keratitis Acanthamoeba Infections in the United States, 1956–2020

Background Acanthamoeba is a free-living ameba that can cause severe disease affecting the central nervous system, skin, sinuses, and other organs, particularly in immunocompromised individuals. These rare but severe infections are often fatal, yet incompletely described. Methods Cases included were either reported to the Centers for Disease Control and Prevention (CDC) Free-Living Ameba program or published in scientific literature. Characteristics of all patients in the United States with laboratory-confirmed non-keratitis Acanthamoeba infections were described using descriptive statistics, and associations with survival were determined using χ2 and Fisher exact tests. Results Of 173 patients identified, 71% were male and the median age was 44 years (range, 0–87 years). Of these, 26 (15%) survived. Most patients (88%) had at least 1 immunocompromising condition, most commonly human immunodeficiency virus (39%), cancer (28%), and solid organ or hematopoietic stem cell transplant (28%). Granulomatous amebic encephalitis (GAE) was the most common disease presentation (71%). Skin (46%), sinuses (29%), lungs (13%), and bone (6%) were also involved. Nearly half of patients (47%) had involvement of >1 organ system. Survival was less frequent among those with GAE (3%, P < .001) compared with cutaneous disease, rhinosinusitis, or multiorgan disease not including GAE. Of 7 who received the currently recommended treatment regimen, 5 (71%) survived. Conclusions Non-keratitis Acanthamoeba infections occur primarily in immunocompromised individuals and are usually fatal. Survival may be associated with disease presentation and treatment. Providers who care for at-risk patients should be aware of the various disease manifestations to improve early recognition and treatment.