Fatal West Nile Encephalomyelitis in a Young Woman with Hypoparathyroidism and Sjögren's Syndrome. Molecular Insights into Viral Neuro-Invasivity.

West Nile virus (WNV) is an arthropod-borne flavivirus first identified in 1937. Over time, WNV has spread globally and is now endemic in Italy. Although most human WNV infections are asymptomatic (80%), less than 1% progress to a neuroinvasive disease with high mortality rates. This case involves a 45-year-old woman with post-surgical hypoparathyroidism and Sjögren's syndrome who developed severe encephalomyelitis linked to WNV, leading to ventilator-associated pneumonia and death. Neuropathological findings revealed a bilaterally cribriform thalamus and reddish punctate lesions near the dentate nucleus of the cerebellum. The trachea and bronchial hilum branches contained whitish foamy liquid. The left lung showed multiple brownish-violet areas, with whitish regions at dissection. The heart appeared unremarkable. A detailed neuropathological examination focused on areas involved in motor control pathways. Tissue samples were stained with hematoxylin and eosin and trichrome techniques, and immunohistochemistry was performed using CD68, CD3, and CD20. A significant damage was observed in the lenticular nucleus and motor thalamus, with prominent concentric vascular calcifications. The cerebellar cortex showed near-total depletion of Purkinje cells. In the spinal cord, CD68 and CD3 positivity was noted in the lateral funiculi, anterior horns, and Clarke's column. Lung findings showed pulmonary edema, chronic emphysema, and bronchopneumonia. The observed CD3 and CD68 positivity confirms that WNV spreads trans-synaptically along motor control pathways. We speculate on the potential molecular mechanisms by which hypoparathyroidism and Sjögren's syndrome may have played a role in the neuroinvasive progression of the disease.