Agammaglobulinemia: Epidemiology, Pathogenesis, Clinical Phenotype, Diagnosis, Prognosis and Management.

Agammaglobulinemia is a type of primary antibody deficiencies, characterized by severe reduction in serum level of all types of immunoglobulins level and absence of B cells in the peripheral blood. X-linked and various autosomal recessive/dominant mutations have been identified underlying the pathogenesis of this disorder. Affected patients present a broad range of clinical manifestations, including respiratory infections, gastrointestinal complications, Enterovirus infections, autoimmunity, and malignancies. This disease can be controlled by different therapeutic strategies. In this review, we describe different aspects of agammaglobulinemia such as epidemiology, pathogenesis, clinical phenotype, diagnosis, management, and prognosis of congenital agammaglobulinemia.

A decision tree for the genetic diagnosis of deficiency of adenosine deaminase 2 (DADA2): a French reference centres experience.

Deficiency of adenosine deaminase 2 (DADA2) is a recently described autoinflammatory disorder. Genetic analysis is required to confirm the diagnosis. We aimed to describe the identifying symptoms and genotypes of patients referred to our reference centres and to improve the indications for genetic testing. DNA from 66 patients with clinically suspected DADA2 were sequenced by Sanger or next-generation sequencing. Detailed epidemiological, clinical and biological features were collected by use of a questionnaire and were compared between patients with and without genetic confirmation of DADA2. We identified 13 patients (19.6%) carrying recessively inherited mutations in ADA2 that were predicted to be deleterious. Eight patients were compound heterozygous for mutations. Seven mutations were novel (4 missense variants, 2 predicted to affect mRNA splicing and 1 frameshift). The mean age of the 13 patients with genetic confirmation was 12.7 years at disease onset and 20.8 years at diagnosis. Phenotypic manifestations included fever (85%), vasculitis (85%) and neurological disorders (54%). Features best associated with a confirmatory genotype included fever with neurologic or cutaneous attacks (odds ratio [OR] 10.71, p = 0.003 and OR 10.9, p < 0.001), fever alone (OR 8.1, p = 0.01), and elevated C-reactive protein (CRP) level with neurologic involvement (OR 6.63, p = 0.017). Our proposed decision tree may help improve obtaining genetic confirmation of DADA2 in the context of autoinflammatory symptoms. Prerequisites for quick and low-cost Sanger analysis include one typical cutaneous or neurological sign, one marker of inflammation (fever or elevated CRP level), and recurrent or chronic attacks in adults.

Investor Outlook: Rising from the Ashes; GSK's European Approval of Strimvelis for ADA-SCID.

GlaxoSmithKline's (GSK) and partner San Raffaele Telethon Institute for Gene Therapy's recent positive European approval for Strimvelis for treatment of severe combined immunodeficiency due to adenosine deaminase deficiency (ADA-SCID) represents the second EU-approved gene therapy and the first γ-retrovirus and first ex vivo gene therapy. In this article we discuss the significance and implications of this historic approval for the broader gene therapy field.

The health status and quality of life of adults with X-linked agammaglobulinemia.

Forty-one adults (mean age 33) with a definitive diagnosis of X-linked agammaglobulinemia (XLA) completed a questionnaire concerning current and past medical problems and quality of life. Thirty-six of the 41 were working full time or were full time students; 18 had not missed any work or school due to infection in the previous year. Their quality of life was equivalent to that of the general US male population. Thirteen of the 41 reported that they had chronic lung disease, and 33 indicated that they had one or more episodes of sinusitis in the preceding year. Arthritis, diarrhea and skin infections were common but not debilitating. The 41 study subjects were more likely to have a prior family history of XLA, and they were more likely to have milder mutations in Btk, the gene responsible for XLA. These results indicate that most adults with XLA are moderately healthy and lead productive lives.

Clinical and mutational characteristics of X-linked agammaglobulinemia and its carrier identified by flow cytometric assessment combined with genetic analysis.

BACKGROUND: X-linked agammaglobulinemia (XLA), caused by mutations in Bruton's tyrosine kinase (BTK ), is the most common form of inherited antibody deficiency. We previously reported that a flow cytometric evaluation of BTK expression in monocytes could easily detect XLA as well as its carrier. OBJECTIVE: Our purpose was to perform further flow cytometric analysis in additional XLA families in Japan. METHODS: In all, 106 hypogammaglobulinemic males (from 91 families) of various ages with a lack of mature B cells (<1%) were investigated. RESULTS: Flow cytometric assessment revealed the deficient BTK expression status in 78 families (93 patients), and mutations in BTK were identified in 76 of 78 families with presumed XLA. Of the patients with normal BTK expression, 2 showed missense mutations in which the normal amount of altered BTK transcript would cause the XLA phenotype. As many as 30% of these patients with XLA were clinically or genetically recognized beyond 5 years of age. Higher concentrations (>300 mg/dL) of serum IgG were evident in the cases diagnosed among adults, seemingly preventing severe infections. Fifty-seven of 70 mothers of patients with BTK deficiency were diagnosed as obligate carriers on the basis of a bimodal BTK expression pattern. Nine of the remaining 13 mothers showing nonmosaic BTK expression had no mutations in 2 alleles; surprisingly, the other 4 mothers had the mutated alleles. CONCLUSIONS: A diagnostic approach based on flow cytometric assessment for XLA should be initially considered in genetic investigation of antibody deficiencies, regardless of the patient's age.

Assessment of male CVID patients for mutations in the Btk gene: how many have been misdiagnosed?

The presentation of hypogammaglobulinaemia in young males without a family history of immunodeficiency can pose a diagnostic problem. In the past, the presence of B-cells has suggested a diagnosis of common variable immunodeficiency (CVID), although genotypic analysis has now clarified that individuals with B cells may have mutations in their Btk gene. In order to address the issue of how many male individuals with a clinical diagnosis of CVID do in fact have mutations in the Btk gene, we analysed a group of 24 male patients. Single-strand conformation polymorphism (SSCP) analysis was used to screen the patient cohort for mutations in the Btk gene. Given the size of the Btk gene, the number of patients in the cohort and the amount of available DNA, multiplex PCR reactions were utilized to span the 19 exons and promoter region of the gene. Where abnormal migration patterns were observed with multiplex PCR reactions, in nine of the 24 patients, the individual Btk gene fragments were re-amplified and analysed again by SSCP. Following this analysis, four patients continued to demonstrate abnormal SSCP migration patterns. However, direct sequencing of the relevant Btk gene fragments for these four CVID patients revealed a mutation in only one patient. The mutation was the previously described polymorphism at position 2031 of Btk gene within exon 18. These results indicate that caution should be taken with the application of SSCP analysis to mutation detection. While it has a role to play in screening large patient cohorts, direct sequencing is a necessary adjunct to such analysis. Finally, the clinical diagnosis of CVID in this cohort successfully excluded males with Btk mutations.

Identification of deletions in the btk gene allows unambiguous assessment of carrier status in families with X-linked agammaglobulinaemia.

Mutations within the btk gene have recently been shown to cause X-linked agammaglobulinaemia (XLA). Altered patterns of DNA restriction fragments are seen by Southern blot analysis of DNA from affected patients with deletions in the btk gene. We have identified seven affected families in which altered restriction fragments can be used to diagnose and confirm the carrier status of female relatives of affected boys and in prenatal diagnosis.

Bronchiectasis in hypogammaglobulinaemia--a computed tomography assessment.

To determine the pattern of bronchiectasis in hypogammaglobulinaemia we reviewed the CT scans of 38 hypogammaglobulinaemic patients. Twenty-two had bronchiectasis, seven had bronchial wall thickening without bronchiectasis and the remaining nine were normal. The middle lobe was the most common site of bronchiectatic involvement, followed by the lower lobes and the lingula. There were no cases of isolated upper lobe involvement. In patients who had bronchial wall thickening without bronchiectasis the middle lobe and lower lobes were again most commonly affected. It is postulated that in these hypogammaglobulinaemic patients bronchial wall thickening represents a stage of bronchial inflammation prior to the development of bronchiectasis. Patients with X-linked agammaglobulinaemia (XLA) develop bronchiectasis at a significantly earlier age than those with 'common variable' hypogammaglobulinaemia (CVH) (P = 0.02). No correlation was found between the serum levels of immunoglobulin classes at diagnosis and the subsequent development of bronchiectasis.

Quantitative assessment of thymus-dependent (t)-cell function in human peripheral blood.

A new micromethod for evaluating lymphocyte responses to phytohemagglutinin (PHA) has been developed and used for the survey of T-cell function in human peripheral blood. The results of lymphocyte responses to PHA stimulation in whole blood culture were expressed in terms of unit volume of blood (50 mul). This new method has eliminated the major uncontrollable factors of conventional methods, and appears to be more correlated with the cell-mediated immunity in vivo.

Assessment of the B-lymphocyte population in agammaglobulinemia.

The population of B lymphocytes was assessed in the blood of 16 patients with agammaglobulinemia using immunofluorescence and EAC1423 reactivity as B-cell markers. Lymphocytes were fractionated on gradients of bovine serum albumin which are capable of separating lymphocytes into B-cell-rich and T-cell-rich populations. There was complete absence of B lymphocytes in the majority of patients with X-linked agammaglobulinemia. Normal or increased numbers of B lymphocytes were found in all patients with common variable agammaglobulinemia.