Case Report: Complement and infection susceptibility

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Diagnosis of complete deficiency of C2

Lennart Truedsson MD/PhD, Section of Microbiology, Immunology and Glycobiology, Dept of Laboratory Medicine, Lund University, Lund, Sweden

Case Presentation

The patient was a 14-year-old girl who has healthy parents and a healthy 11-year-old sister. At 10 days of age, this patient had suffered from sepsis and meningitis. Staphylococcus aureus and group B streptococci (GBS) was detected in umbilical secretions and in cerebrospinal fluid grew GBS. The girl recovered after adequate antibiotic therapy.

At age 14, the patient was suffering of meningitis again, this time caused by Neisseria meningitidis serogroup W-135. The clinical course was mild, the patient showed no neurological symptoms and recovered without complications after treatment with antibiotics.

Evaluation and Diagnosis

Analysis of complement function with the Complement system screen Wieslab® showed no activity for the classical pathway and the lectin pathway but normal activity for the alternative pathway. Further analysis with measurement of individual components in the classical pathway (C1q, C2 and C4) revealed complete deficiency of C2.

Discussion and Conclusion

Increased susceptibility for bacterial infections is seen in several types of complement deficiency. Complete deficiency of C2 as diagnosed here is rare, found in about 1/20 000 individuals. This deficiency is associated with increased susceptibility for infections with encapsulated bacteria such as pneumococci and also increased risk to develop SLE. However, many C2 deficient individuals are believed not to be diagnosed and some appear not to have increased morbidity. Analysis of complement function is the way to detect this deficiency.


Diagnosis of complete deficiency of C2

Lennart Truedsson MD/PhD, Section of Microbiology, Immunology and Glycobiology, Dept of Laboratory Medicine, Lund University, Lund, Sweden

Case Presentation

A girl of 8 years of age had a sudden onset of febrile illness with headache and was taken to hospital. There she was treated with antibiotics for suspected meningitis or sepsis. Culture of cerebrospinal fluid showed growth of meningococci. Once previously when she was 2 years old, she suffered from pneumonia and sepsis caused by pneumococci. There was no family history of infection susceptibility.

Evaluation and Diagnosis

Analysis of the immune system was performed including immunoglobulins and complement. The IgG concentration including IgG subclasses and IgM were all normal. The IgA concentration was subnormal but not as low as in selective IgA deficiency.

Analysis of complement function with the Complement system screen Wieslab® showed no activity for the classical pathway and for the lectin pathway but normal activity for the alternative pathway. Further analysis with measurement of individual components in the classical pathway (C1q, C2 and C4) revealed complete deficiency of C2.

Discussion and Conclusion

Complete deficiency of C2 is associated with increased susceptibility for infections with encapsulated bacteria such as pneumococci and also increased risk to develop SLE. From the results of the functional analysis it is not possible to know if there also is an MBL deficiency since C2 is common to the classical and the lectin pathway. Measurement of MBL is then needed. There is some evidence for that a combination of a deficiency like C2 deficiency when in combination with deficiency of MBL gives increased infection susceptibility.

 

 complement tests Reasons to analyse

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