Educational paper: Syndromic forms of primary immunodeficiency

The syndromic primary immunodeficiencies are disorders in which not only the immune system but also other organ systems are affected. Other features most commonly involve the ectodermal, skeletal, nervous, and gastrointestinal systems. Key in identifying syndromic immunodeficiencies is the awareness that increased susceptibility to infections or immune dysregulation in a patient known to have other symptoms or special features may hint at an underlying genetic syndrome. Because the extraimmune clinical features can be highly variable, it is more difficult establishing the correct diagnosis. Nevertheless, correct diagnosis at an early age is important because of the possible treatment options. Therefore, diagnostic work-up is best performed in a center with extensive expertise in this field, having immunologists and clinical geneticists, as well as adequate support from a specialized laboratory at hand. This paper provides the general pediatrician with the main clinical features that are crucial for the recognition of these syndromes

Control of B Cell Development by the Signaling Proteins Btk and Slp-65

All organisms are continuously challenged by a variety of infectious microbial agents such as viruses, bacteria, fungi and parasites. Therefore the simplest up to the most complex organisms have developed defense mechanisms, to block assaults from hostile micro-organisms. In higher vertebrates this resulted in the development of an immune system consisting of an innate and an adaptive arm. After penetration of the epithelia the innate arm is the fi rst defense line that is encountered, consisting of cells equipped with germline encoded receptors such as Toll like receptor’s (TLR’s) that enable pathogen recognition on the basis of ancient molecular patterns or that detect changes in cell surface composition identifying them as virus infected. Examples of such cells are macrophages, granulocytes and natural killer cells. These cells are supported by an intricate system of soluble anti-microbial proteins such as the complement system, lysozyme and lactoferrin that also provide coverage against micro-organisms. The adaptive arm forms the second line of defense and responds in a highly specifi c way by virtue of somatically rearranged receptors to a microbial challenge, simultaneously generating immunological memory allowing swifter more vigorous responses in future challenges with the same pathogen. The adaptive immune response is carried out by two classes of lymphocytes that are generated from a common lymphoid progenitor in the bone marrow (BM). Progenitors for T cells fi rst migrate to the thymus where they differentiate to become mature helper, cytotoxic and regulatory T cells, whereas progenitors for B cells remain in the BM and develop through several stages into mature B cells. Aberrant lymphoid development in humans may result in various diseases such as immunodefi ciency with increased vulnerability to infections, autoimmunity with immune activation to self-antigens or lymphoproliferation and malignancy. This thesis focuses on the function of two signal transduction proteins Btk and Slp-65 in B cell development and their involvement in immunodefi ciency and malignancy

Hypertension with hidden causes:the cognitive and behavioral profile of an adult female with chronic stress and 16p11.2 microdeletion

This case report aims to alert physicians to neuropsychological features and chromosomal variants that may underly resistant hypertension. We present a 35-year-old female patient with hypertensive crisis (BP 260/160 mmHg), initially treated with a combination of calcium antagonists, beta blockers, diuretics and angiotensin-converting enzyme (ACE)-inhibitors, though with little improvement. Cushing's syndrome, Conn's syndrome, and glucocorticoid receptor deficiency were ruled out. Multidisciplinary examination of medical history and (hetero)anamneses including psychosocial factors revealed mild dysmorphic body features, developmental delay, early diagnosis of autism spectrum disorder, a history of being bullied at school, little peer contact, learning disabilities, and special education. Neuropsychological assessment demonstrated below average to low average intelligence quotient, cognitive impairments, and psychopathology. Parallel genetic analyses revealed a rare 16p11.2 microdeletion syndrome. These concurrent examinations explained the patient's life-long high stress levels. After psychological treatment, with additional support at home, her blood pressure lowered to normal levels and antihypertensive drugs were no longer needed.</p

Tumor suppressor function of Bruton tyrosine kinase is independent of its catalytic activity

During B-cell development in the mouse, Bruton tyrosine kinase (Btk) and the adaptor protein SLP-65 (Src homology 2 [SH2] domain-containing leukocyte protein of 65 kDa) limit the expansion and promote the differentiation of pre-B cells. Btk is thought to mainly function by phosphorylating phospholipase Cgamma2, which is brought into close proximity of Btk by SLP-65. However, this model was recently challenged by the identification of a role for Btk as a tumor suppressor in the absence of SLP-65 and by the finding that Btk function is partially independent of its kinase activity. To investigate if enzymatic activity is critical for the tumor suppressor function of Btk, we crossed transgenic mice expressing the kinase-inactive K430R-Btk mutant onto a Btk/SLP-65 double-deficient background. We found that K430R-Btk expression rescued the severe developmental arrest at the pre-B-cell stage in Btk/SLP-65 double-deficient mice. Moreover, K430R-Btk co

Bruton's Tyrosine Kinase Cooperates with the B Cell Linker Protein SLP-65 as a Tumor Suppressor in Pre-B Cells

Expression of the pre-B cell receptor (pre-BCR) leads to activation of the adaptor molecule SLP-65 and the cytoplasmic kinase Btk. Mice deficient for one of these signaling proteins have an incomplete block in B cell development at the stage of large cycling pre-BCR+CD43+ pre-B cells. Our recent findings of defective SLP-65 expression in ∼50% of childhood pre-B acute lymphoblastic leukemias and spontaneous pre-B cell lymphoma development in SLP-65−/− mice demonstrate that SLP-65 acts as a tumor suppressor. To investigate cooperation between Btk and SLP-65, we characterized the pre-B cell compartment in single and double mutant mice, and found that the two proteins have a synergistic role in the developmental progression of large cycling into small resting pre-B cells. We show that Btk/SLP-65 double mutant mice have a dramatically increased pre-B cell tumor incidence (∼75% at 16 wk of age), as compared with SLP-65 single deficient mice (<10%). These findings demonstrate that Btk cooperates with SLP-65 as a tumor suppressor in pre-B cells. Furthermore, transgenic low-level expression of a constitutive active form of Btk, the E41K-Y223F mutant, prevented tumor formation in Btk/SLP-65 double mutant mice, indicating that constitutive active Btk can substitute for SLP-65 as a tumor suppressor

Hemophilia B in a female with intellectual disability caused by a deletion of Xq26.3q28 encompassing the F9

Background: Hemophilia B is an X-linked recessive disorder caused by mutations in the F9 on Xq27.1. Mainly males are affected but about 20% of female carriers have clotting factor IX activity below 0.40 IU/ml and bleeding problems. Fragile-X syndrome (FMR1) and FRAXE syndrome (AFF2) are well-known causes of X-linked recessive intellectual disability. Simultaneous deletion of both FMR1 and AFF2 in males results in severe intellectual disability. In females the phenotype is more variable. We report a 19-year-old female with severe intellectual disability and a long-standing bleeding history. Methods: A SNP array analysis (Illumina Human Cyto 12-SNP genotyping array) and sequencing of F9 were performed. Laboratory tests were performed to evaluate the bleeding diathesis. Results: Our patient was diagnosed with mild hemophilia B after finding an 11 Mb deletion of Xq26.3q28 that included the following genes among others IDS, SOX3, FMR1, AFF2, and F9. Conclusion: The case history demonstrates that a severe bleeding tendency suggestive of a hemostasis defect in patients with intellectual disability warrants careful hematological and genetic work-up even in the absence of a positive family history

Supplementary data for: Missed Diagnoses and Health Problems in Adults With Prader-Willi Syndrome: Recommendations for Screening and Treatment

Context: Prader-Willi syndrome (PWS) is a complex hypothalamic disorder, combining hyperphagia, hypotonia, intellectual disability, and pituitary hormone deficiencies. Annual mortality of patients with PWS is high (3%). In half of the patients, the cause of death is obesity related and/or of cardiopulmonary origin. Health problems leading to this increased mortality often remain undetected due to the complexity and rareness of the syndrome. Objective: To assess the prevalence of health problems in adults with PWS retrospectively. Patients, Design, and Setting: We systematically screened 115 PWS adults for undiagnosed health problems. All patients visited the multidisciplinary outpatient clinic for rare endocrine syndromes at the Erasmus University Medical Center, Rotterdam, Netherlands. We collected the results of medical questionnaires, interviews, physical xaminations, biochemical measurements, polygraphy, polysomnography, and radiology. Main outcome measures: Presence or absence of endocrine and nonendocrine comorbidities in relation to living situation, body mass index, genotype, and demographic factors. Results: Seventy patients (61%) had undiagnosed health problems, while 1 in every 4 patients had multiple undiagnosed health problems simultaneously. All males and 93% of females had hypogonadism, 74% had scoliosis, 18% had hypertension, 19% had hypercholesterolemia, 17% had type 2 diabetes mellitus, and 17% had hypothyroidism. Unfavorable lifestyles were common: 22% exercised too little (according to PWS criteria) and 37% did not see a dietitian. Conclusions: Systematic screening revealed many undiagnosed health problems in PWS adults. Based on patient characteristics, we provide an algorithm for diagnostics and treatment, with the aim to prevent early complications and reduce mortality in this vulnerable patient group

Development and Function of Immune Cells in an Adolescent Patient with a Deficiency in the Interleukin-10 Receptor

OBJECTIVE:: Monogenic defects in the interleukin-10 (IL-10) pathway are extremely rare and cause infantile-onset inflammatory bowel disease (IBD)-like pathology. Understanding how immune responses are dysregulated in monogenic IBD-like diseases can provide valuable insight in “classical” IBD pathogenesis. Here, we studied long-term immune cell development and function in an adolescent IL-10 receptor (IL10RA)-deficient patient who presented in infancy with severe colitis and fistulizing perianal disease and is currently treated with immune suppressants. METHODS:: Biomaterial was collected from the IL10RA-deficient patient, pediatric IBD patients and healthy controls. The frequency and phenotype of immune cells were determined in peripheral blood and intestinal biopsies by flow cytometry and immunohistochemistry. Functional changes in monocyte-derived dendritic cells and T cells were assessed by in vitro activation assays. RESULTS:: The IL10RA-deficient immune system developed normally with respect to numbers and phenotype of circulating immune cells. Despite normal co-stimulatory molecule expression, bacterial lipopolysaccharide-stimulated monocyte-derived dendritic cells from the IL10RA-deficient patient released increased amounts of TNFα compared to healthy controls. Upon T-cell receptor ligation, IL10RA-deficient peripheral blood mononuclear cells released increased amounts of T cell cytokines IFNγ and IL-17 agreeing with high numbers of T-bet and IL-17 cells in intestinal biopsies taken at disease onset. In vitro, the immunosuppressive drug thalidomide used to treat the patient decreased peripheral blood mononuclear cell-derived TNFα production. CONCLUSIONS:: With time and during immunosuppressive treatment the IL10RA- deficient immune system develops relatively normally. Upon activation, IL-10 is crucial for controlling excessive inflammatory cytokine release by dendritic cells and preventing IFNγ and IL-17-mediated T-cell responses