Recurrent pneumococcal meningitis in a patient with transient IgG subclass deficiency

The genetic basis of pneumococcal and staphylococcal infections: inborn errors of human TLR and IL-1R immunity

Many bacteria can cause pyogenic lesions in humans. Most of these bacteria are harmless in most individuals, but they, nevertheless, cause significant morbidity and mortality worldwide. The inherited and acquired immunodeficiencies underlying these pyogenic infections differ between bacteria. This short review focuses on two emblematic pyogenic bacteria: pneumococcus (Streptococcus pneumoniae) and Staphylococcus, both of which are Gram-positive encapsulated bacteria. We will discuss the contribution of human genetic studies to the identification of germline mutations of the TLR and IL-1R pathways.

Hypermucoviscous Klebsiella syndrome without liver abscess in a patient with immunoglobulin g2 immune deficiency

Background

 Hypermucoviscous Klebsiellapneumoniae (HMVKP) emerged as a cause of invasive infections in South-East (SE) Asia. It has become the most common cause of liver abscess in that region, and it is a significant causative organism in endogenous endophthalmitis and meningitis. During the past decade, cases of this uniquely virulent organism have been reported outside of SE Asia, with a propensity to affect individuals of SE Asian descent. Cases have been reported from North America including Canada.

Methods

 We report a case of a patient of Filipino descent living in Canada who presented with recurrent HMVKP bacteremia in the absence of pyogenic liver abscess or other localized metastatic Klebsiella infection.

Results

 Investigations identified an immunoglobulin (Ig)G2 deficiency and low IgM indicating potential common variable immunodeficiency, and administration of intravenous immunoglobulins was associated with prevention of further recurrences.

Conclusions

 To our knowledge, this is the first report of HMVKP associated with predisposing antibody deficiency.

Epidemiology, etiology, pathogenesis, and diagnosis of recurrent bacterial meningitis

Recurrent bacterial meningitis is a rare phenomenon and generally poses a considerable diagnostic challenge to the clinician. Ultimately, a structured approach and early diagnosis of any underlying pathology are crucial to prevent further episodes and improve the overall outcome for the affected individual. In this article, we are reviewing the existing literature on this topic over the last two decades, encompassing 363 cases of recurrent bacterial meningitis described in 144 publications. Of these cases, 214 (59%) were related to anatomical problems, 132 (36%) were related to immunodeficiencies, and 17 (5%) were related to parameningeal infections. The review includes a detailed discussion of the underlying pathologies and microbiological aspects as well as recommendations for appropriate diagnostic pathways for investigating this unusual entity.

IRAK4 and NEMO mutations in otherwise healthy children with recurrent invasive pneumococcal disease

BACKGROUND

About 2% of childhood episodes of invasive pneumococcal disease (IPD) are recurrent, and most remain unexplained.

OBJECTIVE

To report two cases of otherwise healthy, unrelated children with recurrent IPD as the only clinical infectious manifestation of an inherited disorder in nuclear factor-kappaB(NF-kappaB)-dependent immunity.

RESULTS

One child carried two germline mutations in IRAK4, and had impaired cellular responses to interleukin (IL)1 receptor and toll-like receptor (TLR) stimulation. The other child carried a hemizygous mutation in NEMO, associated with a broader impairment of NF-kappaB activation, with an impaired cellular response to IL-1R, TLR and tumour necrosis factor receptor stimulation. The two patients shared a narrow clinical phenotype, associated with two related but different genotypes.

CONCLUSIONS

Otherwise healthy children with recurrent IPD should be explored for underlying primary immunodeficiencies affecting the IRAK4-dependent and NEMO-dependent signalling pathways.

Candidate genes as potential links between periodontal and cardiovascular diseases

Recent epidemiological associations between periodontal disease and cardiovascular disease have led to a search for biological mechanisms that explain the associations. Genetic factors that influence biological processes involved in both diseases represent one of the potential mechanisms that may link periodontitis and cardiovascular disease. At present, several candidate genes have been investigated in one of the diseases but not the other. Although there are limited data to support a specific candidate gene as the explanation for observed associations between the 2 diseases, a few candidates look promising. One candidate that influences inflammation, interleukin-1 gene polymorphisms, has been associated with periodontal disease and cardiovascular disease. This review will consider biological mechanisms and genes that may be reasonable candidates for an etiological mechanism that influences the clinical characteristics of both periodontal disease and cardiovascular disease.

Antibody deficiency syndromes

Antibodies have a crucial role in protecting against infections, and antibody deficiencies are the commonest primary and secondary immunodeficiencies. Antibody deficiencies may be the only abnormality present in a patient, or they may be present and aggravate the symptoms of various other conditions. Because the presence of an antibody deficiency is difficult to predict from clinical presentation, physicians should perform an evaluation of antibody-mediated immunity, even knowing that, in many cases, the results are normal. When immunizations are included as a part of the evaluation, many patients experience a benefit from enhanced immunity against common pathogens. Some alternative practical approaches to the evaluation of patients with recurrent infections are outlined in Figure 8. Referral to a clinical immunologist can be based on the presence of recurrent infections, a positive family history without prior evaluation by a pediatrician, or abnormal immunologic findings that require an advanced evaluation. In any case, a close collaboration between pediatrician and immunologist likely will result in an accurate diagnosis and better treatment of patients with antibody-deficiency syndromes and their families.

IgG2 immunodeficiency: association to pediatric patients with bacterial meningoencephalitis

An IgG subclass deficiency is often associated with bacterial infections. We studied four pediatric patients suffering from meningoencephalitis, two of them due to Streptococcus pneumoniae and two due to Haemophilus influenzae type b. Simultaneous diagnostic serum and cerebrospinal fluid samples were taken during income. The four subclasses of IgG and albumin were quantified in both biologic fluids by radial immunodiffusion. Very low levels of seric IgG2 with non detectable cerebrospinal fluid IgG2 were found in the patients. No intrathecal IgG subclass synthesis was found in two patients. One patient with S. pneumoniae had IgG3 intrathecal synthesis. Intrathecal IgG1, IgG3 and IgG4 synthesis was found in one patient suffering from H. influenzae according with reibergrams. Substitutive therapy with intravenous gammaglobulin was given to the patients as part of the treatment.

Analysis of IgG subclasses in chronic active Epstein-Barr virus infection

BACKGROUND

Although elevated serum levels of immunoglobulins are frequently observed in patients with chronic active Epstein-Barr virus (EBV) infection, there have been no reports concerning levels of IgG subclasses.

METHODS

Serum levels of IgG subclasses were measured by the enzyme-linked immunosorbent assay (ELISA) in 30 children with severe chronic active EBV infection.

RESULTS

Serum levels of IgG1 were elevated in most patients, except for one who showed an abnormally low level of IgG1 and progressive hypogammaglobulinemia. Serum levels of IgG2, IgG3 and IgG4 in the patients were comparable to those in control children, while abnormally low levels of IgG2, IgG3 and IgG4 were observed in six, three and four cases, respectively.

CONCLUSION

Although not always susceptible to bacterial infections, low levels of IgG2 were frequently observed in patients with chronic active EBV infection and elevated IgG1 is responsible for the increase of serum IgG in these patients.

Immunodeficiency due to a unique protracted developmental delay in the B-cell lineage

A unique immune deficiency in a 24-month-old male characterized by a transient but protracted developmental delay in the B-cell lineage is reported. Significant deficiencies in the number of B cells in the blood, the concentrations of immunoglobulins in the serum, and the titers of antibodies to T-dependent and T-independent antigens resolved spontaneously by the age of 39 months in a sequence that duplicated the normal development of the B-cell lineage: blood B cells followed by immunoglobulin M (IgM), IgG, IgA, and specific IgG antibodies to T-independent antigens (pneumococcal polysaccharides). Because of the sequence of recovery, the disorder could have been confused with other defects in humoral immunity, depending on when in the course of disease immunologic studies were conducted. Investigations of X-chromosome polymorphisms suggested that the disorder was not X linked in that the mother appeared to have identical X chromosomes. An autosomal recessive disorder involving a gene that controls B-cell development and maturation seems more likely. In summary, this case appears to be a novel protracted delay in the development of the B-cell lineage, possibly due to an autosomal recessive genetic defect.