Primary Septic Arthritis of the Hip Caused by Neisseria meningitidis Serogroup W135 in an Infant

Primary septic arthritis due to Neisseria meningitidis is a rare but serious condition, particularly when it presents as monoarticular joint involvement without systemic signs of meningitis or sepsis. Recent case reports highlight the importance of recognizing meningococcal infection in children presenting with acute joint pain, even in the absence of fever or rash.

Understanding Primary Meningococcal Arthritis

Primary meningococcal arthritis (PMA) is defined as acute septic arthritis with isolation of Neisseria meningitidis from synovial fluid or blood cultures, without clinical evidence of meningitis or sepsis. Although uncommon, PMA has been documented in both immunocompetent and immunocompromised individuals, with serogroup B historically being the most frequent cause in many regions.

However, emerging reports indicate that non-B serogroups, including W135, are increasingly implicated in such cases, underscoring the need for heightened clinical awareness and laboratory vigilance.

Case Overview: Infant with Hip Pain and W135 Infection

A documented case involved an infant presenting with acute hip pain as the sole symptom. The child was afebrile and showed no signs of rash or meningococcemia. Clinical evaluation revealed irritability and limited movement of the affected hip. Ultrasound imaging confirmed an effusion, prompting arthrocentesis.

Synovial fluid analysis showed purulent exudate, though initial cultures were negative. Blood cultures, however, grew Neisseria meningitidis, which was subsequently serotyped as group W135. This finding established the diagnosis of primary septic arthritis of the hip due to meningococcal serogroup W135.

The infant received prompt intravenous ceftriaxone, and surgical drainage of the hip joint was performed. Following intervention, the child demonstrated an excellent clinical response with resolution of symptoms and no sequelae reported during follow-up.

Clinical Implications and Diagnostic Considerations

This case reinforces that meningococcal disease should be considered in the differential diagnosis of acute monoarthritis in children, particularly when typical systemic signs are absent. The absence of fever or rash does not exclude meningococcal infection, and reliance on these classic signs may lead to delayed diagnosis.

Healthcare providers are advised to obtain blood cultures and consider joint aspiration in unexplained septic arthritis, especially in young children. Prompt identification of Neisseria meningitidis allows for targeted antibiotic therapy and prevents potential complications such as joint destruction or dissemination.

Epidemiological Context of Serogroup W135

While serogroup B remains predominant in many countries for meningococcal disease, surveillance data from South America have noted an increasing trend in serogroup W135 infections, including cases of arthritis. Reports from Uruguay, Chile, and Argentina have documented PMA caused by serogroup W, suggesting regional shifts in meningococcal epidemiology.

These observations support the need for ongoing serogroup surveillance and may inform future vaccination strategies, particularly in regions where emerging serogroups are gaining clinical significance.

Key Takeaways

• Primary meningococcal arthritis can present with isolated joint pain, even without fever or rash.
• Neisseria meningitidis serogroup W135 has been confirmed as a cause of septic arthritis of the hip in infants.
• Blood cultures may yield positive results when synovial fluid cultures are initially negative.
• Early diagnosis and treatment with appropriate antibiotics (e.g., ceftriaxone) and joint drainage lead to favorable outcomes.
• Clinicians should maintain a high index of suspicion for meningococcal infection in pediatric septic arthritis, regardless of serogroup prevalence.

Frequently Asked Questions

What is primary meningococcal arthritis?

Primary meningococcal arthritis is a rare form of septic arthritis caused by Neisseria meningitidis infection of a joint, occurring without concurrent meningitis or sepsis.

Can meningococcal arthritis occur without fever or rash?

Yes. As demonstrated in published cases, children with meningococcal arthritis may present with joint pain as the only symptom, lacking fever, rash, or other signs of systemic infection.

How is meningococcal arthritis diagnosed?

Diagnosis relies on clinical suspicion, joint aspiration for synovial fluid analysis, and blood cultures. Isolation of Neisseria meningitidis from either site confirms the diagnosis.

What treatment is recommended?

Prompt administration of third-generation cephalosporins, such as ceftriaxone, combined with surgical drainage of the affected joint, is standard of care and associated with excellent recovery.

Is serogroup W135 becoming more common?

In certain regions, particularly parts of South America, there has been a noted increase in meningococcal disease caused by serogroup W135, including atypical presentations like arthritis, highlighting the importance of epidemiological monitoring.