A patient who has had an episode of bacterial meningitis may or may not have an immunodeficiency or other defect in host defense. The pattern of findings and the pathogenic organism involved can help determine what form of investigation is appropriate. The author is from the University of New Mexico in Albuquerque.
Types of host defense defects predisposing to bacterial meningitis:
(1) deficiency immunoglobulins (B cell function) – Bruton (X-linked) agammaglobulinemia, common variable immunodeficiency, X-linked hypogammaglobulinemia with elevated IgM, acquired hypogammaglobulinemia
(2) combined B and T cell immunodeficiency – severe combined immunodeficiency, Wiskott-Aldrich syndrome, immunodeficiency with ataxia and telangiectasia, immunodeficiency with adenosine deaminase or nucleoside phosphorylase deficiency
(3) complement pathway defects – early complement deficiencies (C1, C2, C3), late complement deficiencies (C4, C5, C6, C7, C8, C9), alternative pathway (properdin)
(4) splenic dysfunction – after splenectomy, autosplenectomy (sickle cell disease), congenital asplenia
Some Rules for Patient Evaluation
No workup is required if all of the following are present:
(1) the patient was previously healthy
(2) no history of recurrent infection
(3) no risk factors for HIV disease
(4) not meningococcal disease
If meningococcal disease or disseminated gonococcal infection, consider:
(1) CH50 as screening test
(2) measurement of late complement pathway proteins (C4 – C9) and properdin if suspect defective host response
If adult < 50 years of age with pneumococcal or Listeria meningitis, then screen for HIV disease.
If there is a history of recurrent invasive bacterial infections, or if a single infection occurs in a child earlier (less than 6 months) or later (age 3-4 years) than usual:
(1) measure levels of IgG, IgM, IgE and IgA
(2) CH50 as screening test for complement pathway
(3) HIV testing if risk factors in parents
Reflex testing:
(1) If the patient shows reduced immunoglobulins, then B cells should be evaluated.
(2) If IgA is reduced look for deficiency in IgG subtypes (IgG2 or IgG4).
(3) If IgE is elevated, consider Wiskott-Aldrich syndrome.
(4) measurement of complement proteins and properdin if suspect defective host response, especially after infection with an encapsulated organism
To investigate splenic function:
(1) examine a blood smear for Howell-Jolly bodies
(2) consider radionuclide scan of the spleen and accessory spleens
The presence of thrombocytopenia and abnormally small platelets may indicate Wiskott-Aldrich syndrome.
Specialty: Immunology/Rheumatology, Infectious Diseases
ICD-10: ,