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Absence of the sixth component of complement in a patient with repeated episodes of meningococcal meningitis
Abstract:
A previously healthy 6-year-old boy who presented with meningococcal meningitis responded favorably to ampicillin, but suffered two and possibly three repeat attacks in the ensuing month. No abnormality of the otolarynx, skin, or neuroskeleton was found. The infecting strain, Neisseria meningitidis, Group Y, Type IV, was sensitive to the therapeutic agents used, and antibiotic levels were adequate. Serum bactericidal antibody titers against autologous meningococci were high. Serum complement hemolytic bactericidal activities, however, were entirely lacking, and this was attributable to a complete deficiency of C6. Measurements of the remaining complement components, C-dependent chemotaxis and opsonization, neutrophil function, specific immunity, and the coagulation system, were normal. The parents had half-normal C6 levels. Recurrence of meningitis in this patient supports the concept that complement plays a role in resistance to certain microorganisms and emphasizes the need for complete evaluation of the complement system in individuals with unexplained repeated infections.
Insights
A child with recurrent meningococcal meningitis had a complete deficiency of complement component 6 (C6). This highlights complement
Area of Science:
- Immunology
- Infectious Diseases
- Genetics
Background:
- Recurrent bacterial meningitis can indicate underlying immune deficiencies.
- Neisseria meningitidis infections require robust complement-mediated bacterial killing.
Observation:
- A 6-year-old boy experienced multiple meningococcal meningitis episodes despite appropriate antibiotic treatment and high antibody titers.
- No other immune defects were identified, but serum complement hemolytic activity was absent.
- The patient had a complete deficiency of complement component 6 (C6).
Findings:
- Complete C6 deficiency was identified as the cause of absent serum complement hemolytic activity.
- Normal neutrophil function, specific immunity, and coagulation systems ruled out other contributing factors.
- Parental C6 levels were reduced, suggesting an autosomal recessive inheritance pattern.
Implications:
- This case underscores the critical role of the complement system, specifically C6, in host defense against Neisseria infections.
- Complete complement evaluation is essential for diagnosing unexplained recurrent infections.
- Understanding complement deficiencies aids in managing and preventing severe infectious diseases.