(650) Measurement of IL-6 in Severe Invasive Meningococcal Infection

Introduction: We discuss a case of invasive meningococcal disease (IMD) caused by Neisseria meningitidis and the results of sequential measurements of IL-6. IMD is defined as a disease presenting with bacteremia or meningitis symptoms, where meningococci are identified in blood or cerebrospinal fluid (CSF), or meningococcal genes are detected. IMD is extremely rare in Japan, with an incidence of about 0.03 per 100,000 people and a 15% mortality rate across all age groups. N. meningitidis produces lipooligosaccharides and can cause a severe cytokine storm in the host.

Description: A woman in her 50s who presented at the hospital with impaired consciousness and shock. we diagnosed with septic shock, and treatment included intubation, antimicrobials, catecholamines, continuous hemodiafiltration. IL-6 was abnormally high at 150,000 pg/mL at the time of admission, and it dropped rapidly to below 100 pg/mL the next day. It then did not rise again. Blood cultures confirmed meningococcal meningitis, but CSF examination showed no increase in cell count and negative culture. Despite stabilization of her condition and weaning from catecholamines, the patient experienced prolonged disturbance of consciousness. A diffusion-weighted MRI on day 7 revealed hyperintense signals in both thalami. She gradually regained consciousness and was extubated on day 20, but developed severe quadriplegia. Follow-up MRI showed resolution of the thalamic lesion, but the quadriplegia persisted. A nerve conduction study diagnosed Intensive Care Unit-Acquired Weakness (ICU-AW). The patient was transferred for rehabilitation on day 94.

Discussion: In previous reports, the temporal changes of IL-6 levels were different between survivors and non-survivors: non-survivors maintained high levels, while survivors showed rapid decreases after treatment. On the other hand, IL-6 levels are associated with sepsis-related encephalopathy and ICU-AW occurrence. In this case, the abnormally high initial IL-6 level and its subsequent rapid decrease align with previous reports on sepsis-related encephalopathy and ICU-AW development. We suggest that IL-6 may serve as an indicator of systemic inflammatory disease, with its value potentially predicting severe complications. The trend in IL-6 levels over time may also predict eventual life expectancy.