Tomoaki Suzuki1, Kouichirou Okamoto2, Nobuyuki Genkai3, Akiyoshi Kakita4, Hiroshi Abe5. 1. Department of Neurosurgery, Tachikawa General Hospital, 1-24 Asahioka, Nagaoka 940-8621, Japan; Department of Neurosurgery, Brain Research Institute, Niigata University, 1-757 Asahimachi-Dori, Niigata 951-8585, Japan. Electronic address: t.suzuki2078@gmail.com. 2. Department of Translational Research, Brain Research Institute, Niigata University, 1-757 Asahimachi-Dori, Niigata 951-8585, Japan. Electronic address: oko-okamoto@bri.niigata-u.ac.jp. 3. Department of Neurosurgery, Tachikawa General Hospital, 1-24 Asahioka, Nagaoka 940-8621, Japan. Electronic address: genkai4926@yahoo.co.jp. 4. Department of Pathology, Brain Research Institute, Niigata University, 1-757 Asahimachi-Dori, Niigata 951-8585, Japan. Electronic address: kakita@bri.niigata-u.ac.jp. 5. Department of Neurosurgery, Tachikawa General Hospital, 1-24 Asahioka, Nagaoka 940-8621, Japan. Electronic address: abe0857@tatikawa.or.jp.
Abstract
BACKGROUND: Granulomatous amoebic encephalitis (GAE) is a rare and mostly fatal disease. Without specific symptoms, laboratory findings, or radiologic characteristics, establishing a correct diagnosis is challenging. In many cases of GAE, multiple ring-enhancing lesions with perifocal edema are observed on magnetic resonance imaging (MRI); a solitary and homogeneously enhancing mass masquerading as a malignant lymphoma that evolved into multiple hemorrhagic and necrotic lesions has rarely been reported in GAE. CASE DESCRIPTION: An immunocompetent 68-year-old man presented with transient right hemiparesis due to epilepsy. MRI revealed a well- and homogeneously enhancing mass with perifocal edema and restricted diffusion in the left parietal subcortical region. As malignant lymphoma was suspected based on MRI findings and an elevated β2-microglobulin level in the cerebrospinal fluid, an open biopsy was performed; the pathological diagnosis was inconclusive but suggested a granulomatous disease. Although steroid therapy was administrated, subsequently the mass lesion gradually enlarged. After a second surgery for removal of the mass lesion, multiple hemorrhagic and necrotic lesions developed at the primary site and additionally in the brainstem. The patient entered a comatose state and died 3 months after admission. Histopathological examination and polymerase chain reaction analysis of the specimen revealed posthumously GAE caused by Balamuthia mandrillaris with necrotizing vasculitis. CONCLUSION: A solitary mass lesion initially mimicked a malignant lymphoma, and subsequently evolved into multiple hemorrhagic and necrotic lesions detected on T2*-weighted and susceptibility-weighted imaging. Such serial changes noted on MRI seem characteristic and suggestive of necrotizing vasculitis of GAE.
BACKGROUND:Granulomatous amoebic encephalitis (GAE) is a rare and mostly fatal disease. Without specific symptoms, laboratory findings, or radiologic characteristics, establishing a correct diagnosis is challenging. In many cases of GAE, multiple ring-enhancing lesions with perifocal edema are observed on magnetic resonance imaging (MRI); a solitary and homogeneously enhancing mass masquerading as a malignant lymphoma that evolved into multiple hemorrhagic and necrotic lesions has rarely been reported in GAE. CASE DESCRIPTION: An immunocompetent 68-year-old man presented with transient right hemiparesis due to epilepsy. MRI revealed a well- and homogeneously enhancing mass with perifocal edema and restricted diffusion in the left parietal subcortical region. As malignant lymphoma was suspected based on MRI findings and an elevated β2-microglobulin level in the cerebrospinal fluid, an open biopsy was performed; the pathological diagnosis was inconclusive but suggested a granulomatous disease. Although steroid therapy was administrated, subsequently the mass lesion gradually enlarged. After a second surgery for removal of the mass lesion, multiple hemorrhagic and necrotic lesions developed at the primary site and additionally in the brainstem. The patient entered a comatose state and died 3 months after admission. Histopathological examination and polymerase chain reaction analysis of the specimen revealed posthumously GAE caused by Balamuthia mandrillaris with necrotizing vasculitis. CONCLUSION: A solitary mass lesion initially mimicked a malignant lymphoma, and subsequently evolved into multiple hemorrhagic and necrotic lesions detected on T2*-weighted and susceptibility-weighted imaging. Such serial changes noted on MRI seem characteristic and suggestive of necrotizing vasculitis of GAE.