Case Presentation: A 52-year-old female with a history of poorly controlled type II diabetes and osteoarthritis presented to the emergency department with acute weakness, malaise, chills, and right knee pain. The patient had chronic knee arthritis which acutely worsened over 2 days on the right side associated with swelling with the inability to bear weight. She had no history of trauma to the knee or prior gout. The patient was experiencing homelessness and living in a shelter. Review of systems was negative for headache, photophobia, neck pain, and rash. Vitals on arrival showed a BP of 120/78, pulse of 110 bpm, temperature of 37.6 C, RR of 18, and SpO2 of 100%. On physical exam, the right knee was erythematous and swollen with pain on passive and active range of motion. No other rashes were present. WBC was 15.5 K/mcL, CRP was 60 mg/mL and ESR was 90 mm/hr. Blood cultures on admission grew Neisseria meningitidis. A right knee arthrocentesis was performed, showing a WBC count of 193,200 with negative synovial fluid culture and no crystals. Orthopedics performed an irrigation and debridement of the right knee. The patient had no history of splenectomy. C3 complement level was 133 and C4 was 38, both within normal limits, C5 terminal complement component testing was normal, and an HIV test was negative. The patient was treated with 2g IV ceftriaxone for 4 weeks. At follow-up, the patient recovered without complications.
Discussion: Neisseria meningitidis is typically associated with invasive infections such as meningitis, normally reported in young people. (1,2) However, several case reports indicate N. meningitidis as a rare cause of primary septic arthritis in adults. The knee is the most commonly affected joint. (3) Meningococcal arthritis has three typical presentations: 1) primary meningococcal arthritis, defined as acute septic arthritis without meningitis or signs of meningococcemia; 2) secondary meningococcal arthritis, which is a complication of acute meningococcemia (most common); and 3) tertiary meningococcal arthritis, an uncommon arthritis associated with chronic meningococcemia.(3) Our patient’s presentation of invasive meningococcemia was atypical in that there was no evidence of meningitis. We suspect that the negative synovial cultures were a result of receiving antibiotics prior to arthrocentesis. Our patient had risk factors of poorly controlled type II diabetes and homelessness, which could have put her at risk for invasive N. meningitidis. Due to the rarity of this infection, it is essential to consider additional underlying causes predisposing to N. meningitidis bacteremia such as HIV, complement deficiencies, and asplenia, which were not present in the patient. Primary septic arthritis is usually suspected to be due to N. gonorhoeae. However, prompt identification of N. meningitidis by PCR is important from the public health standpoint since it requires notifying the state health department and contact tracing. (3) There are no established guidelines for septic arthritis secondary to N. meningiditis. A review of the literature indicated that surgical washout is frequently required and antibiotic courses range from 2-6 weeks depending on clinical resolution. (2)
Conclusions: This case represents the importance of considering N. Meningitidis in the differential for septic arthritis. Early recognition of N. meningitidis as the causative agent, surgical drainage, antibiotic therapy, and ruling out underlying causes of immunodeficiency are vital in the management.