Aseptic meningitis as an uncommon presentation of polyarteritis nodosa: a case report with focused literature synthesis

BACKGROUND: Central nervous system (CNS) involvement in polyarteritis nodosa (PAN) is uncommon and typically manifests as ischemic or hemorrhagic events. Presentation as sterile meningitis is rare and may lead to diagnostic delay. CASE PRESENTATION: A 31-year-old man presented with persistent headache, high - grade fever, and nodular erythema on both calves. Cerebrospinal fluid (CSF) analysis demonstrated lymphocyte-predominant pleocytosis with elevated protein levels, initially suggesting a viral meningitis-like presentation. Despite empirical antiviral therapy, his symptoms failed to improve. On hospital day 7, the development of testicular discomfort and the presence of cutaneous nodules prompted further evaluation. Histopathological examination of a skin biopsy revealed fibrinoid necrosis of small arteries with inflammatory cell infiltration, confirming the diagnosis of PAN. Initiation of glucocorticoid therapy resulted in rapid clinical improvement. LITERATURE SYNTHESIS: A focused review of previously reported cases indicates that PAN may rarely present with meningitis-like features characterized by sterile CSF pleocytosis and lack of response to antimicrobial therapy, with marked improvement following immunosuppressive treatment. CONCLUSION: Aseptic meningitis-like presentation may represent an underrecognized CNS phenotype of PAN. In patients with persistent meningitis-like symptoms, negative infectious workup, and concomitant systemic manifestations such as skin nodules or testicular pain, vasculitis should be considered early to avoid diagnostic delay and improve outcomes.