Primary Meningococcal Septic Arthritis in a 58-Year-Old Female

Primary meningococcal septic arthritis (PSMA) is an exceedingly rare manifestation of Neisseria meningitidis infection, characterized by localized joint involvement in the absence of meningitis or systemic meningococcemia. We report a case of a 58-year-old woman who presented with acute septic arthritis in her right knee following a cruise. She was discharged from the emergency department with stable vital signs and negative blood cultures and instructed to follow-up with orthopedics. A synovial fluid analysis revealed gram-negative diplococci consistent with Neisseria sp. The organism was identified as N. meningitidis by culture and successfully treated with surgical incision and drainage and intravenous ceftriaxone. The patient demonstrated clinical improvement without evidence of systemic infection and returned to normal activity after the course of antibiotics. This highlights the importance of including N. meningitidis in the differential diagnosis of septic arthritis even in the absence of systemic symptoms.