Paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis associated with small cell lung cancer and cytotoxic T-cell-mediated pathology: Case report

Abstract

Anti-N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis is caused by a reversible inhibition of ion channel actions by autoantibodies and is associated with a relatively good prognosis. Pathological findings of NMDAR encephalitis usually do not show neurophagorous nodules, but rare or mild inflammatory infiltration. We report a patient of small cell lung cancer (SCLC)-related paraneoplastic encephalitis with NMDAR antibodies, a cytotoxic T-cell-mediated pathology of the brain, and a rapid clinical course. This case highlights that the neuropathological diversity of NMDAR encephalitis may be even broader than previously thought and that NMDAR antibodies may also be found in various pathological conditions with a vigorous immune response.

Keywords: Anti-N-methyl-d-aspartate receptor antibodies; cytotoxic T-cells; paraneoplastic encephalitis; pathology; small cell lung cancer.

Figure 1

Brain MRI showed symmetric increased fluid-attenuated inversion recovery signals in the basal ganglia and medial temporal lobes.

Figure 2

Full-body CT revealed a mass in the right hilar region.

Figure 3

Microscopic images for the globus pallidus (A, C) and lung tumor (B). Blue and orange squares indicate perivascular regions and parenchyma with neurons, respectively. Bars, 50 μm. (D) RT-PCR using total RNA derived from the indicated organs of the patient (D). GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GrB, granzyme B; GRIN1, glutamate ionotropic receptor N-methyl-D-aspartate type subunit 1; Synapt, Synaptophysin; TIA-1, T-cell intracytoplasmic antigen-1.