An Unusual Cause of Central Nervous System Infection During Acute Myeloid Leukemia Induction Chemotherapy: Acanthamoeba Brain Abscess

Excerpt

A 19-year old young adult male was admitted with complaints of low-grade fever of two months duration with multiple petechial rashes all over the body for one week. On routine investigation, hemoglobin was 6.7 g/dl, total white blood cell count was 3200 cells/dl and differential count of 58% polymorphs, 30% lymphocytes and 12% blasts. Bone marrow biopsy with flow cytometry revealed 36% myeloid blasts in bone marrow, confirming diagnosis of acute myeloid leukemia (AML). Cytogenetic study from bone marrow aspirate was normal and FISH studies revealed Inv(16) positive. Patient was started 7 + 3 induction chemotherapy with Cytarabine (100 mg/m² 24-h infusion) and Daunorubicin (90 mg/m²). Day 28 bone marrow revealed normocellular marrow with 6% blasts. Patient was given repeat induction chemotherapy with HAM protocol which included Cytarabine (3 g/m² on D1, 3, 5) with Mitoxantrone (12 mg/m² D4, 5, 6). On day 10 post chemotherapy, patient developed high- grade fever associated with severe holocranial headache. There was no neck rigidity or any focal neurological deficits or papilledema on examination. Absolute neutrophil count at onset of fever was 128 cells/dl. A diagnosis of febrile neutropenia was kept and patient started on Imipenem + Cilastatin along with Vancomycin Contrast enhanced computerized tomogram (CECT) of the head was done which was suggestive of peripherally enhancing hypodense lesion in the right parietal region suggestive of an abscess (Fig. 1a). Cerebrospinal fluid (CSF) study did not show any cells with 45 mg/dl of protein (Normal 15–50 mg/dl) and sugar levels of 46 mg/dl (Normal 40–70 mg/dl). CSF bacterial culture was sterile. Polymerase Chain Reaction (PCR) done for TB bacilli, HSV and Toxoplasma was negative. A contrast enhanced magnetic resonance imaging (CEMRI) of the brain was done which was suggestive of a hemorrhagic ring enhancing parietal lobe lesion suggestive of brain abscess—possibly fungal etiology. Hence liposomal amphotericin 5 mg/kg/day was added. Patient became afebrile within a week of therapy and his headache resolved. Day 28 bone marrow aspiration and biopsy showed no excess blasts. Repeat CEMRI brain revealed an increase in the size as well as number of abscesses (Fig. 1b). A stereotactic biopsy was done along with excision of the right parietal abscess. Smear of the abscess fluid showed multiple cysts suggestive of Acanthamoeba spp. (Fig. 2a). Culture on non nutrient agar showed the presence of Acanthamoeba trophozoites and cysts and were confirmed by PCR (Fig. 2b). Histopathology of the lesion also confirmed multiple cysts with morphology suggestive of Acanthamoeba in the abscess cavity wall. Diagnosis of Acanthamoeba brain abscess was kept and patient started on combination of ketoconazole, rifampicin, trimethoprim-sulfamethoxazole and azithromycin. CSF for PCR taken before starting of definitive treatment was negative for Acanthamoeba species. Patient is now asymptomatic without any complaints of fever, headache, neurological deficits or papilledema. The treatment will further be continued for 4–6 weeks, followed by a repeat MRI at the end of therapy.

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