Dominant negative variants in IKZF2 cause ICHAD syndrome, a new disorder characterised by immunodysregulation, craniofacial anomalies, hearing impairment, athelia and developmental delay.

BACKGROUND: Helios (encoded by IKZF2), a member of the Ikaros family of transcription factors, is a zinc finger protein involved in embryogenesis and immune function. Although predominantly recognised for its role in the development and function of T lymphocytes, particularly the CD4+ regulatory T cells (Tregs), the expression and function of Helios extends beyond the immune system. During embryogenesis, Helios is expressed in a wide range of tissues, making genetic variants that disrupt the function of Helios strong candidates for causing widespread immune-related and developmental abnormalities in humans. METHODS: We performed detailed phenotypic, genomic and functional investigations on two unrelated individuals with a phenotype of immune dysregulation combined with syndromic features including craniofacial differences, sensorineural hearing loss and congenital abnormalities. RESULTS: Genome sequencing revealed de novo heterozygous variants that alter the critical DNA-binding zinc fingers (ZFs) of Helios. Proband 1 had a tandem duplication of ZFs 2 and 3 in the DNA-binding domain of Helios (p.Gly136_Ser191dup) and Proband 2 had a missense variant impacting one of the key residues for specific base recognition and DNA interaction in ZF2 of Helios (p.Gly153Arg). Functional studies confirmed that both these variant proteins are expressed and that they interfere with the ability of the wild-type Helios protein to perform its canonical function-repressing IL2 transcription activity-in a dominant negative manner. CONCLUSION: This study is the first to describe dominant negative IKZF2 variants. These variants cause a novel genetic syndrome characterised by immunodysregulation, craniofacial anomalies, hearing impairment, athelia and developmental delay.

Thromboembolism Incidence and Risk Factors in Children with Cancer: A Population-Based Cohort Study.

There is conflicting information about the epidemiology of thromboembolism (TE) in paediatric oncology. Objectives were to describe the incidence and risk factors of TE in children with cancer. We included all children with cancer less than 15 years of age diagnosed from 2001 to 2016, treated at one of the 12 Canadian paediatric centres outside of Ontario and entered into the Cancer in Young People-Canada database. Potential risk factors for TE were evaluated using Cox proportional hazards regression stratified by haematological malignancies versus solid tumours. Factors associated with vascular access- and non-vascular access-related TE were compared using chi-square or Fisher's exact tests. Of the 7,471 children included, 283 experienced TE requiring medical intervention; cumulative incidence of TE at 5 years was 3.8 ± 0.2% and 0.36% ± 0.07% for life-threatening or fatal TE. For haematological malignancies, the following factors were associated with TE in multivariable regression: age < 1 year, 5 to 9.99 years and 10 to 14.99 years (relative to age 1-4.99 years), haematopoietic stem cell transplant (hazard ratio [HR] = 1.49, 95% confidence interval [CI], 1.00-2.32), anthracyclines (HR = 2.21, 95% CI, 1.12-4.37) and asparaginase (HR = 1.68, 95% CI, 1.15-2.44). For solid tumours, obesity (HR = 1.92, 95% CI, 1.01-3.68), surgery (HR = 2.70, 95% CI, 1.44-5.08), radiation (HR = 47.51, 95% CI, 24.01-94.01), anthracyclines (HR = 2.74, 95% CI, 1.29-5.82) and platinum agents (HR = 2.26, 95% CI, 1.19-4.28) were associated with TE. Life-threatening and fatal TEs were more common among non-vascular access TEs (14.5% vs. 3.3% p = 0.001). In a population-based cohort, 4% of children with cancer developed a clinically significant TE. Accurate risk stratification tools are needed specific to malignancy type.

Application of genomics to identify therapeutic targets in recurrent pediatric papillary thyroid carcinoma.

Children with papillary thyroid carcinoma (PTC) may relapse despite response to radioactive iodine (RAI). Two children with multiply relapsed PTC underwent whole-genome and transcriptome sequencing. A TPM3-NTRK1 fusion was identified in one tumor, with outlier NTRK1 expression compared to the TCGA thyroid cancer compendium and to Illumina BodyMap normal thyroid. This patient demonstrated resolution of multiple pulmonary nodules without toxicity on oral TRK inhibitor therapy. A RET fusion was identified in the second tumor, another potentially actionable finding. Identification of oncogenic drivers in recurrent pediatric PTC may facilitate targeted therapy while avoiding repeated RAI.

Congenital abnormalities of the inferior vena cava presenting clinically in adolescent males.

INTRODUCTION: Congenital anatomic abnormality of the inferior vena cava (IVC) is an important risk factor for the development of spontaneous proximal lower extremity deep vein thrombosis (DVT) in young adults. The incidence of DVT associated with congenital IVC anomalies in paediatric populations has not been described, and the implications of IVC anomalies for treatment and outcomes of DVT are unknown. METHODS: This study reports a series of five adolescent males with spontaneous lower extremity DVTs and underlying congenital IVC abnormalities. Cases were identified by searching the institutional database of patients treated with anticoagulation for venous thromboembolism at a tertiary children's hospital. RESULTS: The demographics, clinical presentations, imaging findings, treatment courses, and outcomes are described. All cases occurred in males, and accounted for approximately twenty percent of adolescent males presenting with DVT. CONCLUSIONS: IVC abnormality is likely an under-recognized risk factor for DVT in this age group, and detailed vascular imaging should be pursued in adolescents with spontaneous proximal lower extremity DVT when initial ultrasonography does not delineate the proximal clot extent. Management requires individual risk-benefit assessment in the context of providing developmentally appropriate care. Further research is required to establish long-term outcomes and determine optimal treatment strategies.

Development of attentional networks in childhood.

Recent research in attention has involved three networks of anatomical areas that carry out the functions of orienting, alerting and executive control (including conflict monitoring). There have been extensive cognitive and neuroimaging studies of these networks in adults. We developed an integrated Attention Network Test (ANT) to measure the efficiency of the three networks with adults. We have now adapted this test to study the development of these networks during childhood. The test is a child-friendly version of the flanker task with alerting and orienting cues. We studied the development of the attentional networks in a cross-sectional experiment with four age groups ranging from 6 through 9 (Experiment 1). In a second experiment, we compared children (age 10 years) and adult performance in both child and adults versions of the ANT. Reaction time and accuracy improved at each age interval and positive values were found for the average efficiency of each of the networks. Alertness showed evidence of change up to and beyond age 10, while conflict scores appear stable after age seven and orienting scores do not change in the age range studied. A final experiment with forty 7-year-old children suggested that children like adults showed independence between the three networks under some conditions.