Germline bi-allelic SH2B3/LNK alteration predisposes to a neonatal juvenile myelomonocytic leukemia-like disorder.

Juvenile myelomonocytic leukemia (JMML) is a rare, generally aggressive myeloproliferative neoplasm affecting young children. It is characterized by granulomonocytic expansion, with monocytosis infiltrating peripheral tissues. JMML is initiated by mutations upregulating RAS signaling. Approximately 10% of cases remain without an identified driver event. Exome sequencing of 2 unrelated cases of familial JMML of unknown genetics and analysis of the French JMML cohort identified 11 patients with variants in SH2B3, encoding LNK, a negative regulator of the JAK-STAT pathway. All variants were absent from healthy population databases, and mutation spectrum was consistent with a loss of function of the LNK protein. A stoploss variant was shown to affect both protein synthesis and stability. The other variants were either truncating or missense, the latter affecting the SH2 domain that interacts with activated JAK. Of the 11 patients, 8 from 5 families inherited pathogenic bi-allelic SH2B3 germline variants from their unaffected heterozygous parents. These children represent half of the cases with no identified causal mutation in the French cohort. They displayed typical clinical and hematological JMML features with neonatal onset and marked thrombocytopenia. They were characterized by absence of additional genetic alterations and a hypomethylated DNA profile with fetal characteristics. All patients showed partial or complete spontaneous clinical resolution. However, progression to thrombocythemia and immunity-related pathologies may be of concern later in life. Bi-allelic SH2B3 germline mutations thus define a new condition predisposing to a JMML-like disorder, suggesting that the JAK pathway deregulation is capable of initiating JMML, and opening new therapeutic options.

Predictors of autoimmune hemolytic anemia in beta-thalassemia patients with underlying red blood cells autoantibodies.

In beta-thalassemia patients, erythrocyte autoantibodies can remain silent or lead to Autoimmune Hemolytic Anemia (AIHA).The aim of this study was to identify predictors of AIHA in beta-thalassemia patients with positive Direct Antiglobulin Test (DAT), in Tunisia. This longitudinal prognosis study was carried out on beta-thalassemia patients with a positive confirmed DAT. Predictors of AIHA were identified the Kaplan-Meier method. A Cox model analysis was used to identify independent predictors. Among 385 beta thalassemia patients, 87 developed positive DAT (22.6%). Autoimmune hemolytic anemia was occurred in 25 patients. Multivariate analysis showed that AIHA was independently associated with beta-thalassemia intermedia and similar family history of AIHA. Splenectomy in patients with positive DAT was independently associated with an increased risk of AIHA (HR = 6.175, CI: 2.049-18.612, p < 0.001). The risk of developing AIHA was higher during the first 72 transfusions. Autoimmune hemolytic anemia was significantly associated with polyspecific DAT (anti-complement and anti-IgG), blood group AB and prior alloimmunization. Whereas transfusion by phenotypic and leukoreduced blood was a protective factor. In summary, splenectomy after autoimmunization, prior alloimmunization, DAT specificity (IgG with complement), thalassemia intermedia, AB blood group and family history of AIHA were strongly associated with AIHA. Leukoreduced blood transfusion had a proven preventive role.

Consanguineous unions and endogamy in families of beta-thalassaemia patients from two Mediterranean populations: Tunisia and Italy.

Background: Consanguinity increases the incidence of recessive diseases such as beta-thalassaemia major (ßTM), one of the most prevalent lethal inherited diseases in the world.Aim: This study aims to identify the frequency of endogamy and consanguinity in two Mediterranean ßTM populations and to study the implication of socio-economic factors.Subjects and methods: A trans-sectional study was conducted in 203 Tunisian families and 75 Italian families. Data were collected using a questionnaire completed by patients and parents.Results: Complete endogamy and consanguinity were observed in 82.75% and 62.56% of Tunisian families, respectively. Complete endogamy was found in 90.67% of Italian families, no consanguinity was noted. The low occupation status of Tunisian mothers was associated with an increasing frequency of consanguinity (p = .01) and endogamy (p = .0003). Consanguinity was associated with low education level (p = .012) and low occupation status (p=.047) of fathers. No significant association was found between endogamy and socio-economic factors in the Italian sample.Conclusions: High consanguinity and endogamy rates in Tunisian families may explain the frequency of ßTM in Tunisia. The high endogamy rate in Italian families could also increase the frequency of ßTM. Identification of geographical distribution and socio-economic factors leading to endogamy and consanguinity in these populations might help to improve ßTM prevention.

Report of the Tunisian Registry of Primary Immunodeficiencies: 25-Years of Experience (1988-2012).

PURPOSE: Primary immunodeficiencies (PIDs) are a large group of diseases characterized by susceptibility to not only recurrent infections but also autoimmune diseases and malignancies. The aim of this study was to describe and analyze the distribution, clinical features and eventual outcome of PID among Tunisian patients. METHODS: We reviewed the record of 710 patients diagnosed with Primary Immunodeficiency Diseases (PIDs) from the registry of the Tunisian Referral Centre for PIDs over a 25-year period. RESULTS: The male-to-female ratio was 1.4. The median age at the onset of symptoms was 6 months and at the time of diagnosis 2 years. The estimated prevalence was 4.3 per 100,000 populations. The consanguinity rate was found in 58.2 % of families. According to the International Union of Immunological Societies classification, spectrums of PIDs were as follows: combined T-cell and B-cell immunodeficiency disorders account for the most common category (28.6 %), followed by congenital defects of phagocyte (25.4 %), other well-defined immunodeficiency syndromes (22.7 %), predominant antibody deficiency diseases (17.7 %), diseases of immune dysregulation (4.8 %), defect of innate immunity (0.4 %) and complement deficiencies (0.4 %). Recurrent infections, particularly lower airway infections (62.3 %), presented the most common manifestation of PID patients. The overall mortality rate was 34.5 %, mainly observed with combined immunodeficiencies. CONCLUSION: The distribution of PIDs was different from that reported in Western countries, with a particularly high proportion of Combined Immunodeficiencies and phagocyte defects in number and/or function. More is needed to improve PID diagnosis and treatment in our country.