Acanthamoeba is the causative agent of granulomatous amebic encephalitis, a rare and usually fatal disease. We report a child with acute lymphoblastic leukemia who developed brain abscesses caused by Acanthamoeba during induction therapy. Multimodal antimicrobial chemotherapy and hyperbaric oxygen therapy resulted in complete resolution of symptoms and of pathology as seen by magnetic resonance imaging.
CASE REPORTA 25-month-old boy was treated at our institution for acute lymphoblastic leukemia (ALL). The induction therapy consisted of prednisone, dexamethasone, vincristine, daunorubicin, l-asparaginase, methotrexate, cyclophosphamide, and mercaptopurine. Infection prophylaxis included oral amphotericin B and trimethoprim-sulfamethoxazole (4 mg/kg of body weight/day 4 days/week). Complete remission of ALL was achieved by day 15 of ALL treatment.Forty-three days after the diagnosis was established and therapy started, the boy developed fever followed by an increase of C-reactive protein (CRP) (maximum, 87.8 mg/liter [normal range, 0 to 8 mg/liter]). Therapy with meropenem and liposomal amphotericin B resulted in defervescence. The patient suffered from mild headache, and 5 days later he experienced left-sided hemiparesis and a second elevation of CRP level (maximum, 37 mg/dl). No other symptoms besides fever and hemiparesis were noted.Magnetic resonance imaging (MRI) revealed multifocal lesions up to 20 mm in diameter, partially necrotic as seen by increased contrast medium enhancement, and extended edema. The largest lesion was located in the right front parietal lobe. The morphology of these lesions was indicative for abscess formations (Fig. 1).Analysis of the initially acquired cerebrospinal fluid (CSF) showed 0 erythrocytes/l, 2 leukocytes/l, increased protein (62 mg/dl), normal glucose, and no bacteria. An extensive diagnostic workup on fungi, bacteria, and parasites known to cause brain abscesses in children (7) revealed positive PCR results for Acanthamoeba 2 days after the first signs of hemiparesis. An Acanthamoeba-specific PCR amplifying a fragment of the 18S ribosomal DNA (rDNA) was performed using the primers JDP1 and JDP2 (12) and Acanthamoeba strain ATCC PRA-105, genotype T4, as a positive control. For genotyping, amplicons were sequenced using a 310 ABI Prism automated sequencer (Applied Biosystems, Langen, Germany), and the genotype was assessed with the model assumption of a Ͻ5% sequence dissimilarity within one genotype (3). Further specification revealed Acanthamoeba group II, genotype T4, known to be the predominant type that causes granulomatous amebic encephalitis (GAE) in humans (13).Cultures and PCR of the CSF were negative for fungi and bacteria. The results of Acanthamoeba PCR of nasal and respiratory discharge and sputum were negative.ALL therapy was stopped on treatment day 44, and empirical antimicrobial therapy was initiated, consisting of meropenem, teicoplanin, fosfomycin, metronidazole, and liposomal amphotericin B. Hyperbaric oxygen therapy (HBO) was started empirically for its...