Fatal Encephalitis in a Case of Hypereosinophilic Syndrome: MRI and Autopsy Findings

Abstract

A 34-year-old man developed fever and headache, followed by finger tremor and gait disturbance, and was admitted to our hospital about two months after onset. Blood tests showed a white blood cell count of 32,600/μL with an eosinophil count of 22,300/μL. There was no evidence of allergic drug reaction or parasitic infection. Cerebrospinal fluid examination demonstrated mononuclear pleocytosis without eosinophils or atypical cells. Brain MRI showed symmetric lesions bilaterally in the medial temporal lobe, frontobasal and insular regions and medulla oblongata. Herpes simplex virus-DNA was negative in the cerebrospinal fluid. The patient died about four months after onset. Histopathologically, there was infiltration of T cells, B cells and macrophages throughout the whole brain, but eosinophils or atypical cells were absent. Immunohistochemistry for herpes simplex virus type 1 and human herpesvirus 6 was negative. This case suggests that fatal encephalitis may develop in association with hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome: a new cause of vasculitis of the central nervous system

“…Of the two remaining case reports, one had a mass lesion with eosinophilic infiltration, and also eosinophilic meningeal infiltration, but no vasculitis [17]. The other showed encephalitis, with a diffuse perivascular infiltrate of lymphocytes and macrophages, but, again, no vasculitis (and no eosinophils) [18].…”

“…No published case has previously showed CNS vasculitis. Indeed, we found only four published accounts of HES with any CNS disease that included histopathology [17][18][19][20]. Of these four, one included almost no pathological detail (being principally an MRI study, but mentioning ''reactive gliosis secondary to infarction with abundant intravascular eosinophils'', [19] without vasculitis), and one did not meet the diagnostic criteria for HES (but nonetheless showed no vasculitis) [20].…”

“…Various neurological complications have been reported [9][10][11][12][13][14][15], but there are extremely few accounts of CNS pathological changes (and none showing vasculitis) [16][17][18][19][20].…”

Eosinophilic meningoencephalitis successfully treated with glucocorticoids and intravenous immunoglobulin: a case report

“…Corticosteroids are widely used as the first-line anti-inflammatory treatment, and most patients show good response to adequate doses [ 3 ]. However, there have been cases where patients continued to deteriorate despite adequate corticosteroid therapy, leading to permanent neurological damage or death [ 4 ]. To date, the use of alternative anti-inflammatory agents in eosinophilic meningoencephalitis has not been reported.…”