Delayed Diagnosis of Amphetamine-Associated CNS Vasculitis Presenting as a Mass Lesion: Case Report and Literature Review

A 41-year-old man with no prior medical history presented with subacute confusion and left-sided weakness. Routine laboratory test results were normal, but toxicologic screening detected cannabinoids and N-methylphenethylamine (amphetamine). Magnetic resonance imaging showed a heterogeneously enhancing right frontotemporal mass concerning for neoplasm. He had 2 nondiagnostic biopsies and continued to decline despite high-dose steroids. A right temporal lobectomy ultimately led to the diagnosis of central nervous system (CNS) vasculitis, attributed to amphetamine use. The patient died and CNS vasculitis was confirmed on autopsy. This case illustrates that CNS vasculitis may present as a mass lesion, which may raise cognitive biases and delay diagnosis.