Look for the Zebra: Complement Deficiency Discovered After Years of Unexplained Headaches

Introduction Recurrent bacterial meningitis in adults is an uncommon clinical phenomenon that necessitates comprehensive investigation for potential anatomical or immunological abnormalities. We present the case of a 40- 50-year-old man with a 40-year history of recurrent pneumococcal meningitis that began at the age of seven. Despite numerous hospitalizations and empirical treatments throughout his childhood and adulthood, the underlying cause remained unidentified until his latest admission. During the admission, the patient exhibited severe headaches, confusion, and agitation. Analysis of cerebrospinal fluid revealed a significantly elevated white cell count (15,705 cells/µL), critically low glucose levels (< 0.2 mmol/L), and the presence of Streptococcus pneumoniae detected via BioFire PCR. Blood and CSF cultures confirmed the presence of penicillin-resistant S. pneumoniae, which was sensitive to third-generation cephalosporins. Immunological assessment showed normal immunoglobulin levels but a notably low total hemolytic complement activity (CH50) of 22.1%, indicating a significant impairment of the classical complement pathway. This finding strongly suggests a primary complement deficiency as the root cause of his recurrent infections. The patient responded to appropriate antimicrobial therapy but was lost to follow-up before a complete complement component analysis could be conducted. Conclusion This case underscores the critical need to evaluate complement function in patients with recurrent encapsulated bacterial infections, especially when these episodes span several decades. Early identification of complement deficiencies can facilitate timely prophylactic measures, vaccination strategies, and genetic counseling, prevent life-threatening complications and enhance long-term outcomes.