Acanthamoeba is a protozoan producing keratitis in the immunocompetent host and disseminated infection with encephalitis in immunocompromised individuals. Diagnosis and treatment of acanthamoeba infections are difficult given the rarity of the infection. We describe a case of disseminated acanthamoebiasis in a previously healthy bilateral lung transplant recipient.
A 60 year-old bilateral lung transplant recipient presented with multiple, non-tender skin nodules over the trunk and extremities. Four weeks prior to presentation, he experienced a laceration on his hand while retrieving a catfish and subsequently developed a subcutaneous nodule on his upper arm. Over the next three weeks, eight other nodules appeared over trunk and extremities. He denied fever, dyspnea, cough or headaches. Prior to this illness, he had experienced an uncomplicated post-transplant course. Medications included tacrolimus, prednisone, mycophenolate and itraconazole. Initial examination revealed a nontoxic-appearing gentleman with firm, nontender, subcutaneous nodules measuring 1-3 cm over the trunk and extremities. A skin punch biopsy was performed revealing granulomatous inflammation and no organisms. Antibacterial agents were initiated for a presumed bacterial skin infection. A complete blood count, tissue cultures, echocardiography and chest radiographs were nondiagnostic. On hospital day four, he developed a focal seizure involving right arm and leg. Magnetic resonance imaging demonstrated areas of increased signal intensity in the frontal and parietal lobes. A lumbar puncture revealed a low glucose, 5 white blood cells and no organisms. On day # 7, he became febrile and developed respiratory failure requiring mechanical ventilation. Bronchoscopy demonstrated intact anastomoses with scant secretions. Bronchoalveolar fluid revealed no organisms. Antibacterial therapy was broadened and antifungal agents prescribed. Several skin lesions developed an eschar and a wide excisional skin biopsy revealed coagulative necrosis. He remained febrile, developed multiorgan failure and expired on hospital day 17. Post mortem examination revealed ulcerative skin lesions without purulence distributed on the trunk and extremities. Gross examination of the lungs revealed multiple nodules and inspection of the brain demonstrated hemorrhagic infarcts. Microscopic examination of lung and brain tissue revealed trophozoites and cysts identified as Acanthamoeba. Meticulous microscopic examination of the skin sections demonstrated Acanthamoeba trophozoites.
Disseminated acanthamoebiasis is characterized by granulomatous infiltration of the skin and brain. The route of transmission appears to be hematogenous after introduction through the skin or airways. Acanthamoeba infection has been described in transplant recipients and HIV positive patients with skin lesions being a frequent initial manifestation. Skin lesions appear as papules, nodules or non-healing ulcers varying 0.5 to 3 cm in size. Microscopic examination characteristically reveals granulomatous inflammation that may also be seen with tuberculosis, tertiary syphilis, sporotrichosis, leprosy and coccidiomycosis. However, granuloma formation may be absent in severely immunocompromised patients. Trophozoites may be mislabeled as large histiocytes and Calcofluor stain allows correct identification. Identification of the cyst form is possible with Gomori Methamine Silver (GMS) staining cysts black and Periodic acid-Schiff (PAS) staining cysts red. Combination therapy with pentamidine, ketoconazole, sulfadiazine, 5-fluorocytosine has been reported, but a standard regimen remains elusive.
Acanthamoebiasis is a rare, infectious complication following transplantation. Transplant recipients with a syndrome of cutaneous lesions and meningoencephalitis should be evaluated for disseminated acanthamoebiasis. Deep skin biopsies using PAS, GMS and Calcofluor stains improve identification. Early recognition and treatment with combination therapy is required for successful treatment.
F. Sattar, None.