CNS vasculitis is a rare condition that is challenging to diagnose and is marked by inflammation in the blood vessels within the brain and spinal cord, which can lead to infarcts, cognitive deficits, and focal neurologic deficits. Tumor necrosis factor alpha (TNF-α) inhibitors have been associated with vasculitis in reported case series.

We present a case of a 26-year-old man with autism spectrum disorder and psoriasis, receiving adalimumab injections for 3 years, who presented with two weeks of progressive gait instability, dysarthria, cerebellar ataxia, and focal seizure with loss of awareness. Investigation revealed numerous T2 hyper-intensities in the pons, cerebellum, and cerebral cortices on MRI brain. Repeat imaging after clinical worsening showed restricted diffusion and micro-hemorrhages. Serum studies were unremarkable. Lumbar puncture revealed elevated CSF protein and lymphocytes, but was otherwise unrevealing. Angiogram was negative. He initially improved on steroids but worsened after tapering. Cerebellar biopsy demonstrated lymphocytic infiltration of blood vessels, concerning for lymphocytic vasculitis without fibrinoid necrosis. He was treated with six cycles of cyclophosphamide, leading to clinical and radiographic improvement.

TNF-α inhibitor-induced vasculitis is a rare but critical complication to identify and treat promptly. Previous reports have noted involvement of cutaneous vessels, peripheral nerves, and kidneys. We present a case of adalimumab-induced CNS vasculitis in a patient who developed cerebellar and brainstem syndrome after three years of treatment for psoriasis, which was clinically and radiographically responsive to cyclophosphamide therapy. This case highlights the importance of recognizing CNS lymphocytic vasculitis in patients on TNF-α inhibitors to reduce morbidity and mortality.