Nina Kathrin Serwas

Atypical manifestation of LRBA deficiency with predominant IBD-like phenotype.

Background:Inflammatory bowel diseases (IBDs) denote a heterogeneous group of disorders associated with an imbalance of gut microbiome and the immune system. Importance of the immune system in the gut is endorsed by the presence of IBD-like symptoms in several primary immunodeficiencies. A fraction of early-onset IBDs presenting with more severe disease course and incomplete response to conventional treatment is assumed to be inherited in a Mendelian fashion, as exemplified by the recent discovery of interleukin (IL)-10 (receptor) deficiency. Methods:We analyzed a patient born to consanguineous parents suffering from severe intestinal manifestations since 6 months of age and later diagnosed as IBD. Eventually, she developed autoimmune manifestations including thyroiditis and type I diabetes at the age of 6 and 9 years, respectively. Combined single-nucleotide polymorphism array-based homozygosity mapping and exome sequencing was performed to identify the underlying genetic defect. Protein structural predictions were calculated using I-TASSER. Immunoblot was performed to assess protein expression. Flow cytometric analysis was applied to investigate B-cell subpopulations. Results:We identified a homozygous missense mutation (p.Ile2824Pro) in lipopolysaccharide-responsive and beige-like anchor (LRBA) affecting the C-terminal WD40 domain of the protein. In contrast to previously published LRBA-deficient patients, the mutant protein was expressed at similar levels to healthy controls. Immunophenotyping of the index patient revealed normal B-cell subpopulations except increased CD21low B cells. Conclusions:We describe a patient with a novel missense mutation in LRBA who presented with IBD-like symptoms at early age, illustrating that LRBA deficiency should be considered in the differential diagnosis for IBD(-like) disease even in the absence of overt immunodeficiency.

Identification of ITK deficiency as a novel genetic cause of idiopathic CD4+ T-cell lymphopenia.

To the editor: Idiopathic CD4 lymphopenia represents a heterogeneous group of combined primary immunodeficiencies with markedly reduced CD4+ T-cell counts. Although several genetic etiologies including MHC class II deficiency[1][1] or mutations in RAG1 ,[2][2] MST1 ,[3][3] or LCK [4][4] have been

Clinical features of interleukin 10 receptor gene mutations in children with very early-onset inflammatory bowel disease.

Objectives: In the present study, we studied a cohort of patients with very early onset inflammatory bowel disease (IBD) to determine the frequency of mutations in the interleukin 10 (IL10) receptor genes as a cause of early-onset IBD. Methods: Sanger sequencing was performed to determine the presence of IL10 and/or IL10 receptor mutations in 17 patients with a diagnosis of very early onset IBD (disease onset <2 years of age in 15 patients, between 3 and 4 years in the other 2). Mutation screening was performed including all of the coding regions of the IL10, IL10RA, and IL10RB genes. We then compared the follow-up findings of the patients with IL10 receptor mutations in terms of demographic, clinical, laboratory, and treatment response properties with those of patients diagnosed as having very early onset IBD with no mutation. Results: We identified 3 patients bearing mutations in the IL10 or IL10 receptor genes, including 1 mutation in IL10RB that has been described recently (c.G477A, p.Trp159*) and 2 novel mutations affecting the IL10RA gene (c.T192G, p.Tyr64* and c.T133G, p.Trp45Gly). Collectively, these mutations thus provided genetic etiology for 17.6% of the cohort under investigation. The presence of a family history of IBD and the clinical course of Crohn disease differed between patients with mutations in the IL-10 pathway and those without such mutations. Although perianal fistulas were found in all of the patients with IL10 receptor mutations, they were found in only 14.3% of those without such mutations. The lower values of weight-for-age and height-for-age z scores, necessity for more intensive therapy, achievement of longer periods until remission, and frequent relapses in the patients bearing mutations in the IL10 receptor genes all underlined the severity of the disease and its relatively poor response to treatment. Conclusions: In spite of the small number of patients with mutations affecting the IL-10 signaling pathway in our study, in all of the patients with IL10 receptor mutations, the disease onset occurs at an early age, the prognosis is poor, and the response to treatment is insufficient.

CD55 Deficiency, Early-Onset Protein-Losing Enteropathy, and Thrombosis

Background Studies of monogenic gastrointestinal diseases have revealed molecular pathways critical to gut homeostasis and enabled the development of targeted therapies. Methods We studied 11 patients with abdominal pain and diarrhea caused by early‐onset protein‐losing enteropathy with primary intestinal lymphangiectasia, edema due to hypoproteinemia, malabsorption, and less frequently, bowel inflammation, recurrent infections, and angiopathic thromboembolic disease; the disorder followed an autosomal recessive pattern of inheritance. Whole‐exome sequencing was performed to identify gene variants. We evaluated the function of CD55 in patients’ cells, which we confirmed by means of exogenous induction of expression of CD55. Results We identified homozygous loss‐of‐function mutations in the gene encoding CD55 (decay‐accelerating factor), which lead to loss of protein expression. Patients’ T lymphocytes showed increased complement activation causing surface deposition of complement and the generation of soluble C5a. Costimulatory function and cytokine modulation by CD55 were defective. Genetic reconstitution of CD55 or treatment with a complement‐inhibitory therapeutic antibody reversed abnormal complement activation. Conclusions CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein‐losing enteropathy (the CHAPLE syndrome) is caused by abnormal complement activation due to biallelic loss‐of‐function mutations in CD55. (Funded by the National Institute of Allergy and Infectious Diseases and others.)

ITK Deficiency: How can EBV be Treated Before Lymphoma?

To the Editor: IL-2 inducible T-cell kinase (ITK) deficiency has been identified as an autosomal recessive form of lymphoproliferative disease.[1] Until now, four different mutations have been identified in the ITK gene including missense (c.C1085T);[1] nonsense (c.C1764G;[2] c.C49T (as in our patients);[3]) and frameshift (c.468delT[4,5]) mutations. Here, we present two affected siblings with a homozygous nonsense mutation in the ITK gene.

Human NF-κB1 Haploinsufficiency and Epstein–Barr Virus-Induced Disease—Molecular Mechanisms and Consequences

Nuclear factor kappa-light-chain-enhancer of activated B cells 1 (NF-κB1)-related human primary immune deficiencies have initially been characterized as defining a subgroup of common variable immunodeficiencies (CVIDs), representing intrinsic B-cell disorders with antibody deficiency and recurrent infections of various kind. Recent evidence indicates that NF-κB1 haploinsufficiency underlies a variable type of combined immunodeficiency (CID) affecting both B and T lymphocyte compartments, with a broadened spectrum of disease manifestations, including Epstein–Barr virus (EBV)-induced lymphoproliferative disease and immediate life-threatening consequences. As part of this review series focused on EBV-related primary immunodeficiencies, we discuss the current clinical and molecular understanding of monoallelic NFKB1 germline mutations with special focus on the emerging context of EBV-associated disease. We outline mechanistic implications of dysfunctional NF-κB1 in B and T cells and discuss the fatal relation of impaired T-cell function with the inability to clear EBV infections. Finally, we compare common and suggested treatment angles in the context of this complex disease.

Novel Mutation in CECR1 Leads to Deficiency of ADA2 with Associated Neutropenia

PurposeAdenosine deaminase 2 (ADA2) have been reported to cause vasculitic diseases and immunodeficiency recently. Patients present with stroke episodes and rashes mimicking polyarteritis nodosa (PAN). We report a patient who has been followed up with severe neutropenia and found an unexpectedly revealed novel mutation in CECR1 affecting ADA2.MethodsWe reviewed medical records and clinical history of the patient. No mutations in other known neutropenia genes such as ELA, G6PC3, HAX1, AP3B1, LAMTOR2, VPS13B, VPS45, GFI1, JAGN1, or WAS could be detected. Sanger sequencing was used to confirm the genetic variants in the patient and relatives.ResultsGenetic analysis by exome sequencing revealed a novel mutation in the gene CECR1 (c.G962A; p.G321E) which segregated perfectly in the relatives.ConclusionThis is the first DADA2 patient presenting with severe neutropenia. We suggest that in patients with unexplained cytopenias combined with immunodeficiency, fevers of unknown origin and high inflammation markers, DADA2 should be considered.

Clinical and Molecular Heterogeneity of RTEL1 Deficiency

Typical features of dyskeratosis congenita (DC) resulting from excessive telomere shortening include bone marrow failure (BMF), mucosal fragility, and pulmonary or liver fibrosis. In more severe cases, immune deficiency and recurring infections can add to disease severity. RTEL1 deficiency has recently been described as a major genetic etiology, but the molecular basis and clinical consequences of RTEL1-associated DC are incompletely characterized. We report our observations in a cohort of six patients: five with novel biallelic RTEL1 mutations p.Trp456Cys, p.Ile425Thr, p.Cys1244ProfsX17, p.Pro884_Gln885ins53X13, and one with novel heterozygous mutation p.Val796AlafsX4. The most unifying features were hypocellular BMF in 6/6 and B-/NK-cell lymphopenia in 5/6 patients. In addition, three patients with homozygous mutations p.Trp456Cys or p.Ile425Thr also suffered from immunodeficiency, cerebellar hypoplasia, and enteropathy, consistent with Hoyeraal-Hreidarsson syndrome. Chromosomal breakage resembling a homologous recombination defect was detected in patient-derived fibroblasts but not in hematopoietic compartment. Notably, in both cellular compartments, differential expression of 1243aa and 1219/1300aa RTEL1 isoforms was observed. In fibroblasts, response to ionizing irradiation and non-homologous end joining were not impaired. Telomeric circles did not accumulate in patient-derived primary cells and lymphoblastoid cell lines, implying alternative pathomechanisms for telomeric loss. Overall, RTEL1-deficient cells exhibited a phenotype of replicative exhaustion, spontaneous apoptosis and senescence. Specifically, CD34+ cells failed to expand in vitro, B-cell development was compromised, and T-cells did not proliferate in long-term culture. Finally, we report on the natural history and outcome of our patients. While two patients died from infections, hematopoietic stem cell transplantation (HSCT) resulted in sustained engraftment in two patients. Whether chemotherapy negatively impacts on the course and onset of other DC-related symptoms remains open at present. Early-onset lung disease occurred in one of our patients after HSCT. In conclusion, RTEL deficiency can show a heterogeneous clinical picture ranging from mild hypocellular BMF with B/NK cell lymphopenia to early-onset, very severe, and rapidly progressing cellular deficiency.

CEBPE-Mutant Specific Granule Deficiency Correlates With Aberrant Granule Organization and Substantial Proteome Alterations in Neutrophils

Specific granule deficiency (SGD) is a rare disorder characterized by abnormal neutrophils evidenced by reduced granules, absence of granule proteins, and atypical bilobed nuclei. Mutations in CCAAT/enhancer-binding protein-ε (CEBPE) are one molecular etiology of the disease. Although C/EBPε has been studied extensively, the impact of CEBPE mutations on neutrophil biology remains elusive. Here, we identified two SGD patients bearing a previously described heterozygous mutation (p.Val218Ala) in CEBPE. We took this rare opportunity to characterize SGD neutrophils in terms of granule distribution and protein content. Granules of patient neutrophils were clustered and polarized, suggesting that not only absence of specific granules but also defects affecting other granules contribute to the phenotype. Our analysis showed that remaining granules displayed mixed protein content and lacked several glycoepitopes. To further elucidate the impact of mutant CEBPE, we performed detailed proteomic analysis of SGD neutrophils. Beside an absence of several granule proteins in patient cells, we observed increased expression of members of the linker of nucleoskeleton and cytoskeleton complex (nesprin-2, vimentin, and lamin-B2), which control nuclear shape. This suggests that absence of these proteins in healthy individuals might be responsible for segmented shapes of neutrophilic nuclei. We further show that the heterozygous mutation p.Val218Ala in CEBPE causes SGD through prevention of nuclear localization of the protein product. In conclusion, we uncover that absence of nuclear C/EBPε impacts on spatiotemporal expression and subsequent distribution of several granule proteins and further on expression of proteins controlling nuclear shape.

Corrigendum: Clinical and Molecular Heterogeneity of RTEL1 Deficiency

[This corrects the article on p. 449 in vol. 8, PMID: 28507545.].