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IntroductionLynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are hereditary cancer syndromes associated with mismatch repair (MMR) deficiency. Tumours show microsatellite instability (MSI), also reported at low levels in non-neoplastic tissues. Our aim was to evaluate the performance of high-sensitivity MSI (hs-MSI) assessment for the identification of LS and CMMRD in non-neoplastic tissues.Materials and methodsBlood DNA samples from 131 individuals were grouped into three cohorts: baseline (22 controls), training (11 CMMRD, 48 LS and 15 controls) and validation (18 CMMRD and 18 controls). Custom next generation sequencing panel and bioinformatics pipeline were used to detect insertions and deletions in microsatellite markers. An hs-MSI score was calculated representing the percentage of unstable markers.ResultsThe hs-MSI score was significantly higher in CMMRD blood samples when compared with controls in the training cohort (pMSH2 carriers (n=5) compared with MSH6 carriers (n=15). The hs-MSI analysis did not detect a difference between LS and control blood samples (p=0.564).ConclusionsThe hs-MSI approach is a valuable tool for CMMRD diagnosis, especially in suspected patients harbouring MMR variants of unknown significance or non-detected biallelic germline mutations.

DOCK2 is a guanine-nucleotide-exchange factor for Rac proteins. Activated Rac serves various cellular functions including the reorganization of the actin cytoskeleton in lymphocytes and neutrophils and production of reactive oxygen species in neutrophils. Since 2015, six unrelated patients with combined immunodeficiency and early-onset severe viral infections caused by bi-allelic loss-of-function mutations in DOCK2 have been described. Until now, the function of phagocytes, specifically neutrophils, has not been assessed in human DOCK2 deficiency. Here, we describe a new kindred with four affected siblings harboring a homozygous splice-site mutation (c.2704-2 A > C) in DOCK2. The mutation results in alternative splicing and a complete loss of DOCK2 protein expression. The patients presented with leaky severe combined immunodeficiency or Omenn syndrome. The novel mutation affects EBV-B cell migration and results in NK cell dysfunction similar to previous observations. Moreover, both cytoskeletal rearrangement and reactive oxygen species production are partially impaired in DOCK2-deficient neutrophils. ispartof: JOURNAL OF CLINICAL IMMUNOLOGY vol:39 issue:3 pages:298-308 ispartof: location:Netherlands status: published

Cernunnos is a DNA repair factor of the nonhomologous end-joining machinery. Its deficiency in humans causes radiosensitive severe combined immune deficiency (SCID) with microcephaly, characterized in part by a profound lymphopenia. In contrast to the human condition, the immune system of Cernunnos knockout (KO) mice is not overwhelmingly affected. In particular, Cernunnos is dispensable during V(D)J recombination in lymphoid cells. Nevertheless, the viability of thymocytes is reduced in Cernunnos KO mice, owing to the chronic activation of a P53-dependent DNA damage response. This translates into a qualitative alteration of the T cell repertoire to one in which the most distal Vα and Jα segments are missing. This results in the contraction of discrete T cell populations, such as invariant natural killer T (iNKT) and mucosa-associated invariant T (MAIT) cells, in both humans and mice.

Activation-induced cell death (AICD) is involved in peripheral tolerance by controlling the expansion of repeatedly stimulated T cells via an apoptotic Fas (CD95; APO-1)–dependent pathway. The TNFRSF-6 gene encoding Fas is mutated in children suffering from autoimmune lymphoproliferative syndrome (ALPS), which is characterized by lymphoproliferation and autoimmunity. We examined AICD in Fas-deficient T cells from ALPS patients. We showed that primary activated Fas-deficient T cells die by apoptosis after repeated T cell antigen receptor (TCR) stimulation despite resistance to Fas-mediated cell death. This Fas-independent AICD was found to be mediated through a cytotoxic granules-dependent pathway. Cytotoxic granules-mediated AICD was also detected in normal T lymphocytes though to a lesser extent. As expected, the cytotoxic granules-dependent AICD was abolished in T cells from Rab27a- or perforin-deficient patients who exhibited defective granules-dependent cytotoxicity. Supporting an in vivo relevance of the cytotoxic granules-dependent AICD in ALPS patients, we detected an increased number of circulating T lymphocytes expressing granzymes A and B. Altogether, these data indicated that the cytotoxic granules-dependent cell death in ALPS may compensate for Fas deficiency in T lymphocytes. Furthermore, they identified a novel AICD pathway as a unique alternative to Fas apoptosis in human peripheral T lymphocytes.

Background Data on anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis are scarce in children. The current study is aimed at describing the clinical features and outcomes of childhood-onset ANCA-associated vasculitis (AAV). Methods We conducted a retrospective French multicentre study involving patients in whom AAV was diagnosed before the age of 18 years. Inclusion criteria were (i) granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) according to classification criteria of the European League Against Rheumatism/Paediatric Rheumatology European Society, and (ii) ANCA positivity. Patient and renal survival were analysed. Results Among 66 children included, 80% were female, 42% had GPA and 58% MPA including renal-limited vasculitis, 67% were pANCA+ and 33% cANCA+. The mean incidence of reported cases increased to 0.45 per million children/year in the period 2006-10. Median age at diagnosis was 11.5 years, and median time to diagnosis was 1 month. Initial symptoms included fever and fatigue (79%), skin lesions (41%), arthritis (42%), pulmonary (45%) and renal involvement (88%). Clinical features were similar between GPA and MPA with the exception of upper airway impairment (28%) specific of GPA. Ninety percent of the patients achieved remission after induction treatment. After a median follow-up of 5.2 years, 4 patients (6%) died, corresponding to a mortality rate of 1.2 per 100 person-years, and 22 patients (34%) developed end-stage renal disease (ESRD). Renal survival was 74, 70 and 59% at 1, 5 and 10 years, respectively. In a multivariable Cox regression model, baseline glomerular filtration rate, ethnic origin, histopathological classification and era of treatment were associated with the occurrence of ESRD. Relapse-free survival was 57% at 5 years and 34% at 10 years of follow-up. Patient and renal outcome did not significantly differ between GPA and MPA. Conclusion Childhood-onset AAV is a rare disease characterized by female predominance, delayed diagnosis, frequent renal impairment and a high remission rate. Baseline GFR and new histopathological classification system are strong predictors of ESRD. Renal survival in childhood AAV has improved over time.

A 5-month-old boy developed splenomegaly, anemia, thrombocytopenia with elevated white cells, monocytosis and immature granulocytes in the peripheral blood. Bone marrow showed dysplasia without blastosis. Increased colony-forming unit-granulocyte-macrophage was found in the peripheral blood, mimicking granulocyte-macrophage colony-stimulating factor hypersensitivity. These findings fulfilled the diagnosis criteria for juvenile myelomonocytic leukemia (JMML), but no mutations in the CBL, NRAS, KRAS, or PTPN11 genes were detected. In addition to these findings severe hypogammaglobulinemia and elevated alkaline phosphatase were present. Bone X-ray showed dense and radiopaque bones with a bone-in-bone appearance characteristic of infantile malignant osteopetrosis (IMO). Genetic mutation in T-cell, immune regulator 1 (TCIRG1) was identified, confirming the diagnosis of IMO. Careful differential diagnosis including osteopetrosis, is therefore recommended in patients with clinical features and hematologic findings consistent with JMML.

Autoimmune lymphoproliferative syndrome (ALPS) is a genetic disorder characterized by early-onset, chronic, nonmalignant lymphoproliferation, autoimmune manifestations, and susceptibility to lymphoma. The majority of ALPS patients carry heterozygous germline (ALPS-FAS) or somatic mutations (ALPS-sFAS) of the TNFRSF6 gene coding for FAS. Although the clinical features of ALPS have been described previously, long-term follow-up data on morbidity and mortality are scarce. We performed a retrospective analysis of clinical and genetic features of 90 ALPS-FAS and ALPS-sFAS patients monitored over a median period of 20.5 years. Heterozygous germline mutations of TNFRSF6 were identified in 83% of probands. Somatic TNFRSF6 mutations were found in 17% of index cases (all located within the intracellular domain of FAS). Sixty percent of the ALPS-FAS patients with mutations in the extracellular domain had a somatic mutation affecting the second allele of TNFRSF6; age at onset was later in these patients. No other genotype-phenotype correlations could be found. Long-term analysis confirmed a trend toward spontaneous remission of lymphoproliferation in adulthood but mixed outcomes for autoimmune manifestations. We observed significant and potentially life-threatening disease and treatment-related morbidity, including a high risk of sepsis after splenectomy that calls for careful long-term monitoring of ALPS patients. We also noted a significantly greater occurrence of disease-related symptoms in male than in female patients.

MKD causes hyper-IgD syndrome and mevalonic aciduria. Disease severity and clinical phenotype has not yet been linked to specific mutations. In this study, we intended to review clinical presentation and outcome of pediatric and adult patients. 40 patients were identified through MVK mutation database in one central reference laboratory and physicians' networking. Medical charts were reviewed (21/40) or questionnaires were filled in by treating physician (19/40). Follow-up ranged from 2 years to 60 years. First symptoms occurred before age 2 in 90% of patients. Main clinical features were fever (100%), abdominal pain (92%), diarrhea (88%), enlarged lymph nodes (88%), skin rash (86%), arthralgias (85%), arthritis (43%), growth delay (33%), CNS white matter involvement (7,5%) and macrophage activation syndrome (5%). We recorded 3 disease-related deaths. IgD level ranged from normal (

Varicella-Zoster (VZV) virus, Cytomegalovirus (CMV) and Epstein Barr virus (EBV) infections may have a severe course in patients on immunosuppressive treatments. Data in Juvenile Idiopathic Arthritis (JIA) patients on biologics are still limited.