Neurosarcoidosis or granulomatosis with polyangiitis? A complex case of a brain mass

Sarcoidosis is an immune-mediated systemic disease characterised by the presence of non-caseating granulomas in various parts of the body in the absence of another defined aetiology. Neurologic involvement [neurosarcoidosis (NS)], which occurs in 5-10% of patients with the disease, encompasses a range of clinical and histopathological manifestations that can lead to significant morbidity and mortality. We present a case of a young man with a history of chronic sinusitis, who developed sudden headache associated with seizures. After thorough clinical and paraclinical evaluation, the diagnosis of NS was made once other neurovascular, infectious, metabolic, tumour-related, and immune-mediated aetiologies were ruled out. NS can present as a large dural mass due to nodular pachymeningitis, which can be clinically indistinguishable from other entities such as neoplasms and granulomatosis with polyangiitis. Isolated central nervous system involvement in this entity is rare and usually it is associated with other systemic manifestations. More aggressive management is required to treat this form of sarcoidosis presentation. NS represents a diagnostic challenge and requires ruling out more common entities such as infectious and non-infectious causes like granulomatosis with polyangiitis.