Three novel mutations reflect the variety of defects causing phenotypically diverse X-linked hyper-IgM syndrome

Diagnosis of Hyper IgM syndrome in a Previously Healthy Adolescent Boy Presented with Cutaneous and Cerebral Cryptococcosis

X-linked hyper IgM (X-HIGM) syndrome is a combined immunodeficiency disease caused by mutations in the CD40LG gene, leading to a defect in immunoglobulin (Ig) class switching recombination and effector T-cell responses. X-HIGM patients usually present in early life with pyogenic bacterial and opportunistic infections. Herein, we report a previously healthy 13-year-old Thai boy who first presented with cutaneous and meningoencephalitis cryptococcosis. Whole-exome sequencing revealed that he was hemizygous for a missense c.514T>C (p.Tyr172His) in CD40LG, confirming a diagnosis of X-HIGM. This report demonstrates that X-HIGM could have an age of onset in teens and systemic cryptococcosis could be its presenting symptoms.

Genomic characterization of Mycobacterium tuberculosis lineage 7 and a proposed name: 'Aethiops vetus'

Lineage 7 of the Mycobacterium tuberculosis complex has recently been identified among strains originating from Ethiopia. Using different DNA typing techniques, this study provides additional information on the genetic heterogeneity of five lineage 7 strains collected in the Amhara Region of Ethiopia. It also confirms the phylogenetic positioning of these strains between the ancient lineage 1 and TbD1-deleted, modern lineages 2, 3 and 4 of Mycobacterium tuberculosis. Four newly identified large sequence polymorphisms characteristic of the Amhara Region lineage 7 strains are described. While lineage 7 strains have been previously identified in the Woldiya area, we show that lineage 7 strains circulate in other parts of the Amhara Region and also among foreign-born individuals from Eritrea and Somalia in The Netherlands. For ease of documenting future identification of these strains in other geographical locations and recognizing the place of origin, we propose to assign lineage 7 strains the lineage name 'Aethiops vetus'.

Immunoglobulin class switch recombination deficiency type 1 or CD40 ligand deficiency: from bedside to bench and back again

The immunoglobulin class switch recombination deficiency or hyper-IgM syndrome is characterized by normal or elevated serum IgM and low serum levels of other immunoglobulins. Since the first reported patient with hyper-IgM, more than 200 patients with this phenotype resulted from CD40 ligand deficiency have been reported. However, in addition to this common finding, they presented with different manifestations like opportunistic infections, autoimmunity and malignancies each of them are worth a detailed look. In this review, we will focus on different underlying mechanisms of these presentations to review what we have learned from our patients. In the end, we will discuss different treatment options available for these patients using this knowledge.

Successful haploidentical PBSCT with subsequent T-cell addbacks in a boy with HyperIgM syndrome presenting as severe congenital neutropenia

HIGM syndrome is a group of primary immunodeficiency disorders characterized by recurrent bacterial and opportunistic infections; it is also associated with normal to elevated serum IgM levels and a concomitant deficiency of IgG, IgA, and IgE. In this report, we give account of a boy with X-linked HIGM and a novel Y172C mutation within his CD40LG gene. He presented with severe neutropenia as the dominating symptom. His bone marrow showed maturation arrest at the promyelocyte/myelocyte stage, typical of congenital neutropenia. This boy suffered from life-threatening infections and required high doses of rhG-CSF, and a haploidentical PBSCT was also successfully performed, thus leading to reconstitution of CD40L expression on activated CD4+ T cells (as assessed with flow cytometry six months after the procedure). Two low-dose T-cell addbacks were required to re-establish full donor chimerism and clear CMV reactivation. The report demonstrates that in select cases, alternative donor allogeneic HSCT supported by DLI may be effective in correcting the defect in X-linked HIGM, and HSCT in HIGM children is not necessarily limited to matched sibling donor transplantation.

Reduced transmissibility of East African Indian strains of Mycobacterium tuberculosis

Background

Mycobacterium tuberculosis (MTB) has been classified into 4 main lineages. Some reports have associated certain lineages with particular clinical phenotypes, but there is still insufficient information regarding the clinical and epidemiologic implications of MTB lineage variation.

Methods

Using large sequence polymorphisms we classified MTB isolates from a population-based study in Montreal, Canada into the 4 major lineages, and identified the associated clinical and epidemiologic features. In addition, IS6110-RFLP and spoligotyping were used as indicators of recent TB transmission. The study population was divided into a derivation cohort, diagnosed between 2001 and 2007, and a separate validation cohort, diagnosed between 1996 and 2000.

Results

In the derivation cohort, when compared to the other MTB lineages, the East African-Indian (EAI) lineage was associated with lower rates of TB transmission, as measured by: positive TST among close contacts of pulmonary TB cases (adjusted odds ratio 0.6: [95% confidence interval 0.4–0.9]), and clustered TB cases (0.3: [<0.001–0.6]). Severe forms of TB were also less likely among the EAI group (0.4: [<0.001–0.8]). There were no significant differences when comparing patients with the other MTB lineages. In the validation cohort, the EAI lineage was associated with lower rates of positive TST among contacts (0.5: [0.3–0.9]) and a trend towards less clustered TB cases (0.5: [0.1–1.8]) when compared to the other lineages. Disease severity among the different groups was not significantly different in the validation cohort.

Conclusions

We conclude that in Montreal, EAI strains were associated with reduced transmission compared to other MTB lineages.

Phylogenetic analysis of the promoter region of the CD40L gene in primates and other mammals

CD40L is a type II membrane protein comprised of 261 amino acids. CD40L plays a crucial role in the immune system where it is primarily expressed on activated T cells and triggers immunoglobulin class switching. The genetic disease X-linked hypergammaglobulinemia (HIGM1, XHIGM or XHIM) is caused by mutations in the CD40L gene. Individuals with HIGM1 are susceptible to recurrent infections to pathogens and a relationship has been shown to exist with malaria [Sabeti, P., Usen, S., Farhadian, S., Jallow, M., Doherty, T., Newport, M., Pinder, M., Ward, R., Kwiatkowski, D., 2002a. CD40L association with protection from severe malaria. Genes Immun. 3, 286-291]. In this paper, we phylogenetically examine the promoter region of CD40L in primates and other mammals via phylogenetic shadowing. This analysis revealed several regions of the CD40L promoter that were highly constrained and thereby inferred to be functional. These constrained regions confirmed many known regulatory sites. In addition, a novel, highly constrained upstream region was also identified which had an NF-AT recognition motif. These analyses also showed that the different mammal groups do not share an exactly similar set of promoter binding sites and taxon-specific promoters have evolved.

X-Linked Hyper-Immunoglobulin M Syndrome: Molecular Genetic Study and Long-Time Follow-Up of Three Generations of a Chinese Family

BACKGROUND

X-linked hyper-immunoglobulin M (IgM) syndrome (XHIGM) is a rare immunodeficiency disease caused by mutations of the CD40 ligand gene. Patients are subject to recurrent infections and have normal or elevated levels of IgM but markedly decreased serum IgG.

OBJECTIVE

We describe molecular genetic studies and clinical manifestations in three generations of one family, as well as results of long-term treatment of 2 young men with the disorder.

METHODS

Of 37 living family members, mutational analysis of the CD40 ligand gene was performed in 36 members. Laboratory data for patients and carriers were reviewed.

RESULTS

Four male family members had died of unexplained causes. The 3 patients with XHIGM syndrome and the 5 carriers all had a novel mutation located at Tyr 169 Asn (T526A) in exon 5, the tumor necrosis factor domain of the CD40 ligand gene. In the 3 patients, CD40 ligand expression in activated CD4+ T cells was below 1%. In the carriers, about half of activated CD4+ cells expressed CD40 ligand. One carrier had malignant lymphoma. Long-term (>20 years) intravenous immunoglobulin therapy in 2 patients improved IgG levels but did not fully suppress the high levels of IgM, nor did it prevent late complications (bronchiectasis and sclerosing cholangitis).

CONCLUSIONS

Diagnosis of a genetic immunodeficiency, especially an X-linked disease such as XHIGM syndrome, should prompt a survey of the entire family.

Cryptococcal meningitis in a patient with X-linked hyper-IgM1 syndrome

A case is reported of cryptococcal meningitis in a 27-y-old male suffering from X-linked hyper-IgM1 syndrome. This congenital disorder is characterized by multiple infections of the respiratory and gastrointestinal tracts, but also opportunistic infections commonly seen in patients with cell-mediated immunity. His clinical recovery was good but the need for life-long secondary chemoprophylaxis to prevent relapses is unknown.

Common variable immunodeficiency: test indications and interpretations

Common variable immunodeficiency (CVID) is a primary immunodeficiency disorder that can present with multiple phenotypes, all of which are characterized by hypogammaglobulinemia, in a person at any age. A specific genetic defect that accounts for all CVID phenotypes has not been identified, and it is likely that several distinct genetic disorders with similar clinical presentations are responsible for the observed variation. In this review, we summarize the known genetic mutations that give rise to hypogammaglobulinemia and how these gene products affect normal or abnormal B-cell development and function, with particular emphasis on CVID. Additionally, we describe specific phenotypic and genetic laboratory tests that can be used to diagnose CVID and provide guidelines for test interpretation and subsequent therapeutic intervention.