Variants Disrupting CD40L Transmembrane Domain and Atypical X-Linked Hyper-IgM Syndrome: A Case Report With Leishmaniasis and Review of the Literature.

X-linked hyper-IgM (XHIGM) syndrome is caused by mutations of the CD40LG gene, encoding the CD40L protein. The clinical presentation is characterized by early-onset infections, with profound hypogammaglobulinemia and often elevated IgM, susceptibility to opportunistic infections, such as Pneumocystis jirovecii pneumonia, biliary tract disease due to Cryptosporidium parvum, and malignancy. We report a 41-year-old male presenting with recurrent leishmaniasis, hypogammaglobulinemia, and myopathy. Whole-exome sequencing (WES) identified a missense variant in the CD40LG gene (c.107T>A, p.M36K), involving the transmembrane domain of the protein and a missense variant in the carnitine palmitoyl-transferase II (CPT2; c.593C>G; p.S198C) gene, leading to the diagnosis of hypomorphic XHIGM and CPT2 deficiency stress-induced myopathy. A review of all the previously reported cases of XHIGM with variants in the transmembrane domain showcased that these patients could present with atypical clinical features. Variants in the transmembrane domain of CD40LG act as hypomorphic generating a protein with a lower surface expression. Unlike large deletions or extracellular domain variants, they do not abolish the interaction with CD40, therefore preserving some biological activity.

Progressive choreodystonia in X-linked hyper-IgM immunodeficiency: a rare but recurrent presentation.

An association between movement disorders and immune-system dysfunction has been described in the context of rare genetic diseases such as ataxia telangiectasia as well as infectious encephalopathies. We encountered a male patient who presented immunodeficiency of unknown etiology since childhood. A medication-refractory, progressive choreodystonic movement disorder emerged at the age of 42 years and prompted an exome-wide molecular testing approach. This revealed a pathogenic hemizygous variant in CD40LG, the gene implicated in X-linked hyper-IgM syndrome. Only two prior reports have specifically suggested a causal relationship between CD40LG mutations and involuntary hyperkinetic movements. Our findings thus confirm the existence of a particular CD40LG-related condition, combining features of compromised immunity with neurodegenerative movement abnormalities. Establishing the diagnosis is crucial because of potential life-threatening immunological complications.

CD40LG mutations in Vietnamese patients with X-linked hyper-IgM syndrome; catastrophic anti-phospholipid syndrome as a new complication.

BACKGROUND: X-linked hyper-IgM syndrome (XHIGM) is a rare primary immunodeficiency caused by CD40 ligand defects. METHODS: We identified three patients with XHIGM in Ho Chi Minh City, Vietnam. Whole-exome sequencing, immunological analyses and western blot were performed to investigate phenotypic and genotypic features. RESULTS: Despite showing symptoms typical of XHIGM, including recurrent sinopulmonary infections, oral ulcers and otitis media, the diagnosis was significantly delayed. One patient developed anti-phospholipid syndrome, which has been documented for the first time in XHIGM syndrome. Two patients had elevated IgM levels and all of them had low IgG levels. Exome sequencing revealed mutations in the CD40LG gene: one novel splicing mutation c.156+2T>A and two previously characterised mutations (non-frameshift deletion c.436_438delTAC, stop-gain c.654C>A). Due to these mutations, the CD40 ligand was not expressed in any of the three patients, as demonstrated by western blot analysis. CONCLUSION: This is the first report of XHIGM syndrome in Vietnam indicates that an effective diagnostic strategy, such as sequencing analysis, contributes to reliable diagnosis and subsequent therapy.

Mitochondrial DNA insert into CD40 ligand gene-associated X-linked hyper-IgM syndrome.

BACKGROUND: X-linked hyper-IgM (X-HIGM), which results from mutations in the CD40LG gene located on chromosome Xq26.3, is the most common form of HIGM. To date, more than 130 variants of the CD40L gene have been reported. We described a patient with novel de novo nuclear mitochondrial DNA sequences (NUMTs) in the CD40LG gene that have resulted in X-HIGM. METHODS: Whole-exome sequencing (WES) analysis was used to screen for causal variants in the genome, and the candidate breakpoint was confirmed by Sanger sequencing. RESULTS: A new mutation of CD40LG, which deletes A at position 17 followed by a 147-nucleotide from mitochondrial DNA copies insertion in exon 1, was detected in a 20-month-old boy harbouring an X-HIGM combined with immunodeficiency syndrome. CONCLUSION: This is one of the few cases of a human genetic disease caused by nuclear mitochondrial DNA sequences (NUMTs). The presented data serve to demonstrate that de novo NUMT transfer of nucleic acid is a novel mechanism of X-HIGM.

Complex preimplantation genetic tests for Robertsonian translocation, HLA, and X-linked hyper IgM syndrome caused by a novel mutation of CD40LG gene.

PURPOSE: To perform complex preimplantation genetic tests (PGT) for aneuploidy screening, Robertsonian translocation, HLA-matching, and X-linked hyper IgM syndrome (XHIGM) caused by a novel mutation c.156 G>T of CD40LG gene. METHODS: Reverse transcription PCR (RT-PCR) and Sanger sequencing were carried out to confirm the causative variant of CD40LG gene in the proband and parents. Day 5 and D6 blastocysts, obtained by in vitro fertilization (IVF) with intracytoplasmic sperm injection, underwent trophectoderm (TE) biopsy and whole genomic amplification (WGA) and next generation sequencing (NGS)-based PGT to detect the presence of a maternal CD40LG mutation, aneuploidy, Robertsonian translocation carrier, and human leukocyte antigen (HLA) haplotype. RESULTS: Sanger sequencing data of the genomic DNA showed that the proband has a hemizygous variant of c. 156 G>T in the CD40LG gene, while his mother has a heterozygous variant at the same position. Complementary DNA (cDNA) of CD40LG amplification and sequencing displayed that no cDNA of CD40LG was found in proband, while only wild-type cDNA of CD40LG was amplified in the mother. PGT results showed that only one of the six tested embryos is free of the variant c.156 G>T and aneuploidy and having the consistent HLA type as the proband. Meanwhile, the embryo is a Robertsonian translocation carrier. The embryo was transplanted into the mother's uterus. Amniotic fluid testing results are consistent with that of PGT. A healthy baby girl was delivered, and the peripheral blood testing data was also consistent with the testing results of transplanted embryo. CONCLUSIONS: The novel mutation of c. 156 G>T in CD40LG gene probably leads to XHIGM by nonsense-meditated mRNA decay (NMD), and complex PGT of preimplantation genetic testing for monogenic disease (PGT-M), aneuploidy (PGT-A), structural rearrangement (PGT-SR), and HLA-matching (PGT-HLA) can be performed in pedigree with both X-linked hyper IgM syndrome and Robertsonian translocation.

A Novel CD40L Mutation Associated with X-Linked Hyper IgM Syndrome in a Chinese Family.

Background: Mutations in CD40 ligand gene (CD40L) affecting immunoglobulin class-switch recombination and somatic hypermutation can result in X-Linked Hyper IgM Syndrome (HIGM1, XHIGM), a kind of rare serious primary immunodeficiency disease (PID) characterized by the deficiency of IgG, IgA and IgE and normal or increased serum concentrations of IgM. The objective of this study is to explain genotype-phenotype correlation and highlight the mutation responsible for a Chinese male patient with XHIGM.Methods: Whole exome sequencing (WES) and Sanger sequencing validation were performed to identify and validate the likely pathogenic mutation in the XHIGM family.Results: The results of the sequencing revealed that a new causative mutation in CD40L (c.714delT in exon 5, p.F238Lfs*4) which leads to the change in amino acids (translation terminates at the third position after the frameshift mutation) appeared in the proband. As his mother in the family was carrier with this heterozygous mutation, the hemizygous mutation in this patient came from his mother indicating that genetic mode of XHIGM is X-linked recessive inheritance.Conclusion: This study broadens our knowledge of the mutation in CD40L and lays a solid foundation for prenatal diagnosis and genetic counseling for the XHIGM family.

CD40 Ligand Deficient C57BL/6 Mouse Is a Potential Surrogate Model of Human X-Linked Hyper IgM (X-HIGM) Syndrome for Characterizing Immune Responses against Pathogens.

Individuals with X-HIGM syndrome fail to express functional CD40 ligand; consequently they cannot mount effective protective antibody responses against pathogenic bacteria. We evaluated, compared, and characterized the humoral immune response of wild type (WT) and C57-CD40L deficient (C57-CD40L(-/-)) mice infected with Citrobacter rodentium. Basal serum isotype levels were similar for IgM and IgG3 among mice, while total IgG and IgG2b concentrations were significantly lower in C57-CD40L(-/-) mice compared with WT. Essentially IgG1 and IgG2c levels were detectable only in WT mice. C57-CD40L(-/-) animals, orally inoculated with 2 × 10(9) CFU, presented several clinical manifestations since the second week of infection and eventually died. In contrast at this time point no clinical manifestations were observed among C57-CD40L(-/-) mice infected with 1 × 10(7) CFU. Infection was subclinical in WT mice inoculated with either bacterial dose. The serum samples from infected mice (1 × 10(7) CFU), collected at day 14 after infection, had similar C. rodentium-specific IgM titres. Although C57-CD40L(-/-) animals had lower IgG and IgG2b titres than WT mice, C57-CD40L(-/-) mice sera displayed complement-mediated bactericidal activity against C. rodentium. C. rodentium-infected C57-CD40L(-/-) mice are capable of producing antibodies that are protective. C57-CD40L(-/-) mouse is a useful surrogate model of X-HIGM syndrome for studying immune responses elicited against pathogens.

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.

Molecular Diagnostic Challenges and Complex Management of Consecutive Twin Pregnancies in a Family with CD40 Ligand Deficiency.

X-linked hyper-IgM syndrome (XHIGM) is a primary immunodeficiency disorder (PID) caused by mutation in the gene encoding the CD40 ligand (CD40L) expressed on activated T cells. Prenatal genotyping in carriers with twin pregnancies is more challenging than in women with singleton pregnancies. In addition, women with twin pregnancies may decide on selective termination for which the risk of loss of the healthy foetus may exceed 7%. We report here on a family affected by XHIGM. Diagnosis of the disease was made in a male patient as late as 33 years of age. After family screening, the sister of the proband conceived male twins in two consecutive pregnancies. In the first pregnancy, one of the male foetuses was hemizygous for the c.521A>G (Q174R) mutation in the CD40L gene. In the second pregnancy, ultrasound scan showed one foetus to have exencephaly and karyotyping revealed this foetus to have trisomy 18. Several options were discussed, but the parents decided on selective termination in both pregnancies. The interventions were successful in both cases, and the mother now has two healthy sons. This report demonstrates the way in which advanced technologies in molecular medicine and obstetric interventions may assist families with decisions about possible selective termination in case of life-threatening molecular or chromosomal disorders. Diagnosis of CD40L deficiency at the age of 33 years in the proband was striking and indicated that PIDs are still neglected as disease entities in the evaluation of patients with recurrent severe infectious diseases.

The role of CD40/CD40 ligand interactions in bone marrow granulopoiesis.

The CD40 ligand (CD40L) and CD40 are two molecules belonging to the TNF/TNF receptor superfamily, and their role in adaptive immune system has widely been explored. However, the wide range of expression of these molecules on hematopoietic as well as nonhematopoietic cells has revealed multiple functions of the CD40/CD40L interactions on different cell types and processes such as granulopoiesis. CD40 triggering on stromal cells has been documented to enhance the expression of granulopoiesis growth factors such as granulocyte-colony-stimulating factor (G-CSF) and granulocyte/monocyte-colony-stimulating factor (GM-CSF), and upon disruption of the CD40/CD40L-signaling pathway, as in the case of X-linked hyperimmunoglobulin M (IgM) syndrome (XHIGM), it can lead to neutropenia. In chronic idiopathic neutropenia (CIN) of adults, however, under the influence of an inflammatory microenvironment, CD40L plays a role in granulocytic progenitor cell depletion, providing thus a pathogenetic cause of CIN.

CD40 ligand deficiency with grade III liver fibrosis, transplanted by a treosulphan-based conditioning regimen.

X-linked Hyper IgM is characterized by an absence of the CD40 ligand on activated T lymphocytes resulting in defects of both cellular and humoral immunity. Patients usually present with recurrent bacterial and opportunistic infections. Chronic liver disease is seen in about 75% of patients as a complication. Here, we report a 3.5-year-old boy with X-linked Hyper IgM referred to our clinic for bone marrow transplant. He was transplanted from an HLA-identical sibling donor using a new conditioning agent, treosulphan, together with cyclophosphamide. Since 6 months of age, he has had recurrent respiratory infections, and his XHIGM was diagnosed when he was 1.5 years old. The diagnosis was confirmed by sequence analysis of the CD40L gene. On physical examination, growth failure, bilateral fine crackles in both lungs, and hepatosplenomegaly were detected. The results of his liver function tests were abnormal, and a liver biopsy showed grade III fibrosis and compensated cirrhosis. After conditioning with treosulphan (12 g/m(2)/d x 3 d) and cyclophosphamide (50 mg/kg/d x 4 d), bone marrow from his HLA-identical sister was infused. CD40L expression on activated lymphocytes of the patient was 84% on day +21. His posttransplant period was uneventful. He is now at posttransplant 2 years, with full donor chimerism, and mild, chronic, graft-versus-host disease on his tongue. In conclusion, treosulphan is a new agent for conditioning regimen with less toxicity in patients with severe liver disease.

Partial immune reconstitution of X-linked hyper IgM syndrome with recombinant CD40 ligand.

X-linked hyper IgM syndrome (XHM) is a combined immune deficiency disorder caused by genetic alterations in CD40 ligand. The purpose of this study was to investigate the safety and efficacy of recombinant CD40 ligand (rCD40L) in the treatment of the disease. Three children were administered rCD40L subcutaneously 3 times per week at 0.03 mg/kg for 22 weeks, and after a 12-week drug-free interval, the dose was increased to 0.05 mg/kg for an additional 22 weeks of treatment. Although specific antibody responses to T cell-dependent antigens was lacking, administration of rCD40 resulted in acquisition of the capacity to mount cutaneous delayed type hypersensitivity reactions that disappeared during the drug-free interval as well as the postbiologic follow-up period. With rCD40L treatment, patient T cells developed a new capacity to respond to T-cell mitogens with synthesis of IFN-γ and TNF-α. Intracellular cytokine staining studies showed that both CD4(+) and CD8(+) T cells participated in this response. Finally, CD40L therapy was associated with changes in lymph node size and architecture based on comparison of biopsies taken before and after therapy. This clinical study showed that rCD40L is capable of improving T cell-immune function in patients with XHM.

CD40 ligand deficiency: neurologic sequelae with radiographic correlation.

Patients with CD40 ligand deficiency are susceptible to central nervous system infections, but to date the neurologic progression or long-term outcome of central nervous system complications have not been reported in detail. Characterizing the central nervous system complications of immune deficiencies can lead to the identification of new pathogens. For this study, clinical data were reviewed on patients with both CD40 ligand deficiency and neurodegeneration, identified from a larger cohort of 31 patients. Five patients had progressive neurologic and cognitive decline in the absence of clinical signs of acute fulminant encephalitis, with anatomic brain abnormalities and high mortality (60%). Despite multiple evaluations, no pathogens were identified in four patients, all of whom were on standard intravenous immunoglobulin therapy at illness presentation. This clinical phenotype of progressive decline without acute fulminant encephalitis is similar to chronic enteroviral encephalitis in X-linked agammaglobulinemia, another condition with severe humoral immune defects. Whether infection secondary to subtherapeutic levels of central nervous system immunoglobulin G (IgG), inadequately protective levels of serum IgG, or impaired CD40 ligand-dependent IgG-independent antiviral responses contributed remains undetermined. Emerging gene-chip techniques applied in patients with primary immune deficiencies may identify heretofore unknown viruses. Prospective neurocognitive and evaluation of patients with CD40 ligand deficiency may identify affected patients before overt clinical signs appear.

Impaired maintenance of naturally acquired T-cell memory to the meningococcus in patients with B-cell immunodeficiency.

The importance of T cells in the generation of antigen-specific B-cell immunity has been extensively described, but the role B cells play in shaping T-cell memory is uncertain. In healthy controls, exposure to Neisseria meningitidis in the upper respiratory tract is associated with the generation of memory T cells in the mucosal and systemic compartments. However, we demonstrate that in B cell-deficient subjects with X-linked agammaglobulinemia (XLA), naturally acquired T-cell memory responses to meningococcal antigens are reduced compared with healthy control patients. This difference is not found in T-cell memory to an obligate respiratory pathogen, influenza virus. Accordingly, we show that meningococcal antigens up-regulate major histocompatibility complex (MHC) class II, CD40, CD86/80 expression on mucosal and systemic associated B cells and that antigen presentation stimulates T-cell proliferation. A similar reduction in N meningitidis but not influenza antigen-specific T-cell memory was observed in subjects with X-linked hyper IgM syndrome (X-HIM), implicating the interaction of CD40-CD40L in this process. Together, these data implicate B cells in the induction and maintenance of T-cell memory to mucosal colonizing bacteria such as N meningitidis and highlight the importance of B cells beyond antibody production but as a target for immune reconstitution.

Poorly differentiated gastroenteropancreatic neuroendocrine carcinoma associated with X-linked hyperimmunoglobulin M syndrome.

Gastroenteropancreatic neuroendocrine tumors are uncommon tumors representing 2% of all gastrointestinal tumors. We report a case of a 21-year-old man with X-linked hyperimmunoglobulin M (hyper-IgM) syndrome who presented with diarrhea and jaundice. An ultrasound and magnetic resonance imaging showed multiple variable-sized lesions in the liver and peripancreatic lymphadenopathy. The morphologic and immunohistochemical features of the biopsies from the liver and lymph node were consistent with poorly differentiated neuroendocrine carcinoma. Hyper-IgM syndrome is a rare primary immunodeficiency disease characterized by low serum IgG, IgA, and IgE levels with normal or elevated IgM levels. These patients are at a higher risk for developing malignancies, particularly adenocarcinoma of the gastrointestinal tract and lymphoma. A review of the literature of gastroenteropancreatic neuroendocrine tumors is presented with the discussion of a possible relationship of these tumors with immunodeficiency.

X-linked hyper-IgM syndrome associated with a rapid course of multifocal leukoencephalopathy.

OBJECTIVE: To report an exceptional association between X-linked hyper-IgM syndrome and progressive multifocal leukoencephalopathy. DESIGN: Clinical, immunological, and histological analysis. Patient A 19-year-old male patient with X-linked hyper-IgM syndrome developed typical signs and symptoms of progressive multifocal leukoencephalopathy. RESULTS: The serum level of IgA was decreased; the serum level of IgM was slightly increased; and the serum level of IgG was normal as a result of monthly infusions of immunoglobulin. The expression of CD40 ligand on T cells was markedly reduced in the patient. Magnetic resonance imaging indicated confluent lesions involving the majority of the right hemisphere with a mass effect. The patient died after 6 weeks despite combined antiviral treatment. CONCLUSION: Progressive multifocal leukoencephalopathy may follow a rapid course in patients with X-linked hyper-IgM syndrome because of global defects of cellular and B cell responses.

c-Rel plays a key role in deficient activation of B cells from a non-X-linked hyper-IgM patient.

Our previous results demonstrated that B cells from a patient (pt1) with non-X-linked hyper-IgM syndrome (HIGM) possess an atypical CD23(lo) phenotype that is unaffected by CD40-mediated activation. To investigate the molecular mechanism underlying defective CD23 expression in pt1 B cells, we used lymphoblastoid cell lines that express LMP1 under the control of a tetracycline-inducible promoter (LCL(tet)). Our analysis revealed that the CD23(lo) phenotype in the pt1-LCL(tet) cells is a direct consequence of diminished CD23 transcription. We demonstrate a marked decrease in c-Rel-containing complexes that bind to the proximal CD23a/b promoters in pt1-LCL(tet) extracts, resulting from an overall lower expression of c-Rel in pt1-LCL(tet) cells. Analysis of c-Rel mRNA revealed relatively equal amounts in pt1-LCL(tet) and control LCL(tet) cells, indicating that diminished c-Rel protein expression is unrelated to decreased transcription. Finally, a critical role for c-Rel in CD23 regulation was demonstrated by effectively altering c-Rel expression that resulted in the direct modulation of CD23 surface expression. Collectively, these findings demonstrate that low levels of c-Rel are the underlying cause of aberrant CD23 expression in pt1 B cells and are likely to play a critical role in the pathophysiology of this form of HIGM.