Neisseria meningitidis as a cause of isolated bilateral polyarticular native knee joint septic arthritis

Abstract

• Septic Arthritis is a medical emergency with a high mortality and morbidity. • Early recognition of Septic Arthritis is crucial to preserve joint integrity. • Primary Meningococcal Arthritis can present with atypical clinical features. • PCR testing can prove invaluable in identifying bacterial DNA. • Neisseria Meningitidis is a fastidious organism not easy to culture. Septic Arthritis is a medical emergency with a significant mortality and morbidity. Infection usually occurs via haematogenous seeding of microorganisms or via injury, such as trauma or surgery. The aim of management is to minimise the risk of irreversible joint damage and to preserve function. Septic arthritis is usually bacterial in origin, most commonly Staphylococcus aureus , but Mycobacteria or fungi can also be responsible. Neisseria meningitidis is an aerobic Gram-Negative Diplococcus that normally inhabits the naso and oropharynx and has the potential to cause meningitis, septicaemia, septic arthritis and endocarditis. We present the case of a 63 year old lady admitted with bilateral knee pain and swelling, lower limb rash and a fever who was initially managed as a Reactive Arthritis but subsequent Polymerase Chain Reaction (PCR) molecular analysis revealed capsular group B N. meningitidis in bilateral knee aspirates. We discuss the diagnostic challenges in differentiating Septic Arthritis from inflammatory arthritis, and the role of PCR molecular analysis in that process.