Balamuthia mandrillaris infection in China: A retrospective report of 28 cases.

Balamuthia mandrillaris infection is a rare and fatal disease. It has been reported globally, with most cases reported in the US. We have recorded 28 cases of Balamuthia mandrillaris infection during the past 20 years. The diagnosis was confirmed by immunohistochemical staining with polyclonal anti-Balamuthia antibody and polymerase chain reaction amplification with specific primers. Eighteen patients (64%) were male and 10 (36%) were female. Patient age ranged from 3 to 74 (mean, 27) years; 14 (50%) patients were children. Patient locations were distributed among 12 separate Provinces in China. Twenty-seven (96%) patients lived in rural areas, and 17 (61%) patients reported a history of trauma before the appearance of skin lesions. All cases presented with skin lesions as the primary symptom, and 16 (57%) cases developed encephalitis. Histopathology of skin lesions revealed granulomatous changes with histiocytes, lymphocytes, and plasma cells infiltration. Amebas were identified in all cases with immunohistochemical staining. Follow-up information was available in 27 (96%) cases. Fifteen (56%) patients died due to encephalitis and 12 (44%) were free of disease after treatment. Our results show that the clinical characteristics of Balamuthia mandrillaris infection in China are very different from those in the US. Infection of traumatized skin may play an important role in the pathogenesis of the disease in China. Encephalitis usually develops 3-4 years after skin lesions in Chinese cases. Patients with only skin lesions have a higher cure rate than patients with encephalitis.