Histopathological investigation in Glycine receptor antibody positive progressive encephalomyelitis with rigidity and myoclonus (PERM): A case report.

OBJECTIVE

Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a rare autoimmune neurologic disorder associated with antibodies against the glycine receptor (GlyR). Neuropathologic descriptions are limited. We here report clinical and autopsy findings of a patient with GlyR antibody-associated PERM.

METHODS

Comprehensive postmortem neuropathologic examination was performed using routine histology, immunohistochemistry, and immunofluorescence across neocortical, subcortical, brainstem, cerebellar, and spinal cord regions. Antibodies included GAD65/67, GlyR, IBA1, CD163, GFAP, CD3, and CD20.

RESULTS

A 68-year-old man presented with rapidly progressive trismus, bulbar dysfunction, rigidity, myoclonus and ataxia. Symptoms eventually progressed resulting in respiratory failure and cardiac arrest. Work up was remarkable for positive CSF GlyR antibody confirming the diagnosis of GlyR antibody-associated PERM. Autopsy demonstrated preserved neuronal architecture despite severe clinical disease. The motor cortex demonstrated focal neuropil vacuolation, mild myelin pallor, and prominent microglial activation in the motor cortex, with abnormal foaming, vacuolated cytoplasm appearance. Microgliosis was identified within the thalamus, basal ganglia, amygdala, substantia nigra, dentate nucleus, and spinal cord. Despite the patient's cardiopulmonary arrest, eosinophilic ("red") neurons, diffuse neuronal dropout, and infarct-type tissue injury were not identified. Significant T-cell or B-cell infiltrates and concomitant Alzheimer's disease neuropathologic changes were absent.

CONCLUSIONS

This case expands the limited neuropathologic literature on GlyR antibody-associated PERM by demonstrating pathological changes involving cortical, subcortical, cerebellar, brainstem, and spinal cord regions with preserved neuronal architecture and widespread microglial activation. Additional autopsy studies are needed to define the spectrum and reproducibility of these findings.