Very-early Onset Research Articles

OP17 IBD ulcers are characterized by bioactive interleukin-1 and transcriptomic hallmarks of stromal cell state reprogramming

Abstract Background The programs that perpetuate the inflammation and prevent epithelial repair in Inflammatory Bowel Disease (IBD) remain unclear. Interleukin (IL)-1 plays a role in the maintenance of mucosal homeostasis but also in IBD. Expansion of IL-1 expressing myeloid cells is a hallmark of IBD tissue, including severe and anti-TNF unresponsive disease, and IL-1 expression is highly localized to ulcer beds. However, little is known about the presence of bioactive IL-1 proteins in the cell-free mucosal environment of IBD, nor whether IL-1-driven programs affect epithelial regeneration in IBD ulcers. Methods We established a highly sensitive assay (~500-fold greater than ELISA) to assess bioactive extracellular IL-1 from previously cryopreserved IBD biopsies. We assessed a cohort of Crohn’s Disease (CD, n=23), Ulcerative Colitis (UC, n=18) and non-IBD (n=17) patients, with biopsies from paired inflamed/uninflamed regions (primarily colon but also ileal). We assessed IL-1 bioactivity, including IL-1α vs IL-1β contributions, and performed RNA-seq of samples’ matched cellular compartments. An ulcer-associated gene signature was interrogated in a single-cell (sc)RNA-seq cohort (n=42) of very early onset (VEO)IBD including monogenic disorders, as well as publicly available IBD bulk RNA-seq datasets and scRNA-seq of mouse models of colitis. Results IL-1α and IL-1β bioactivity corresponded with disease and ulcer severity in CD and UC. The most extreme signals were seen in select CD patients with deep ulceration. IL-1α was the predominant contributor to total IL-1 bioactivity in most patients although several with ulcers displayed IL-1β predominance. IL-1 bioactivity correlated with IL-1 transcripts in matched RNA-seq, and weighted gene co-expression network analysis revealed a compelling ulcer-specific module. This module contained transcription factors and genes related to cell state, validated in publicly available datasets (e.g. RISK cohort of ileal CD and scRNA-seq of murine DSS colitis), that when interrogated in a scRNA-seq dataset of VEOIBD (including patients with IL-10RA mutations characterized by deep ulcers), suggests an orchestrated IL-1-driven myeloid/stromal response to epithelial ulceration involving cell state reprogramming and loss of key myofibroblast populations. Conclusion Mucosal ulceration in IBD is associated with bioactive IL-1α and IL-1β proteins, and transcriptomic evaluation of the same correlates with bioactive signal. An ulcer-associated gene module, validated in other datasets, sheds light on IL-1 biology in intestinal epithelial repair. Results strongly suggest the IL-1 signaling pathway being an attractive and precision-based therapeutic target in subsets of IBD patients.

P071 Neonatal levels of inflammatory markers in individuals who later develop early onset Inflammatory Bowel Disease

Abstract Background The early life period is suggested to be important in development of Inflammatory Bowel Disease (IBD). Studies in babies from mothers with IBD observed increased faecal calprotectin and changes in the microbial compartments compared to babies from healthy mothers1,2, which suggests that changes in early life might be associated with later disease development. Prospective studies of IBD risk following early life changes at the molecular level are sparse. We aimed to investigate if individuals with early onset (EO) IBD had changes in systemic inflammatory markers shortly after birth. Methods We measured the concentration of 9 cytokines in a cohort of 464 neonatal dried blood spot samples stored at the Danish National Biobank from individuals who later developed EO IBD (median age of diagnosis 11 years), as well as matched controls. Individuals who developed IBD were identified through the use of the Danish National Patient Registry. Uni- and multivariate logistic regression with adjustment for birth year, sex, and gestational age was conducted to assess the association between 6 of the inflammatory markers with later disease development (INF-γ, TNF-α, IL-1β, IL-4, IL-6 and IL-17a). Further exploratory analyses were performed investigating risk of very early onset (VEO) IBD (onset from 0-5 years) in 88 cases and their matched controls. Results No significant association with EO IBD was observed for any of the cytokines in uni- and multivariate models when adjusting for multiple testing. In the exploratory analysis of VEO IBD, increased IL-4 was associated with significantly reduced risk of IBD (OR=0.992, p-value=0.023) and increased IL-17a was borderline-significantly associated with increased risk of IBD (OR=1.002, p-value=0.063) in a multivariate logistic model including all 6 cytokines. This association did not remain significant when adjusting for multiple testing, which may reflect limited power. Conclusion In our unique study of 464 dried blood spots from later IBD patients and controls, we could not find an association between measured cytokines and EO IBD. In contrast, patients with VEO IBD had decreased levels of IL-4 and increased levels of IL-17a. This sub-cohort was small, and significance disappeared after adjusting for multiple testing. Still, we find it important to report these findings, as they are novel and may inspire future studies into the aetiology of VEO IBD. 1. Kim, E. S. et al. Longitudinal Changes in Fecal Calprotectin Levels Among Pregnant Women With and Without Inflammatory Bowel Disease and Their Babies. Gastroenterology (2021) 2. Torres, J. et al. Infants born to mothers with IBD present with altered gut microbiome that transfers abnormalities of the adaptive immune system to germ-free mice. Gut (2020)

АУТОСОМНО-ДОМИНАНТНАЯ ПОЛИКИСТОЗНАЯ БОЛЕЗНЬ ПОЧЕК С ОЧЕНЬ РАННИМ НАЧАЛОМ

Both autosomal dominant polycystic kidney disease and autosomal recessive polycystic kidney disease may occur at any age starting infancy and up to adulthood. Manifestations of autosomal dominant polycystic kidney disease usually occur in adult patients with a risk of development of end-stage renal failure after the fifth decade of life. However, an increase in the number of pediatric cases of a very-early onset of the disease, in utero or during the first 18 months of life, had been registered recently, that were characterized by severe clinical manifestations which in tis turn had mimic the autosomal recessive polycystic kidney disease. The three infant cases of autosomal dominant polycystic kidney disease are observed in the Article with perinatal period features, clinical manifestations of the disease, tests’ results and its interpretation given. Children with very-early onset of autosomal dominant polycystic kidney disease are in the high-risk group for nephromegaly, severe hypertension and the early end-stage renal failure.

The genetic basis of onset age in schizophrenia: evidence and models.

Schizophrenia is a heritable neurocognitive disorder affecting about 1% of the population, and usually has an onset age at around 21-25 in males and 25-30 in females. Recent advances in genetics have helped to identify many common and rare variants for the liability to schizophrenia. Earlier evidence appeared to suggest that younger onset age is associated with higher genetic liability to schizophrenia. Clinical longitudinal research also found that early and very-early onset schizophrenia are associated with poor clinical, neurocognitive, and functional profiles. A recent study reported a heritability of 0.33 for schizophrenia onset age, but the genetic basis of this trait in schizophrenia remains elusive. In the pre-Genome-Wide Association Study (GWAS) era, genetic loci found to be associated with onset age were seldom replicated. In the post-Genome-Wide Association Study era, new conceptual frameworks are needed to clarify the role of onset age in genetic research in schizophrenia, and to identify its genetic basis. In this review, we first discussed the potential of onset age as a characterizing/subtyping feature for psychosis, and as an important phenotypic dimension of schizophrenia. Second, we reviewed the methods, samples, findings and limitations of previous genetic research on onset age in schizophrenia. Third, we discussed a potential conceptual framework for studying the genetic basis of onset age, as well as the concepts of susceptibility, modifier, and "mixed" genes. Fourth, we discussed the limitations of this review. Lastly, we discussed the potential clinical implications for genetic research of onset age of schizophrenia, and how future research can unveil the potential mechanisms for this trait.

Clinical and genetic characteristics of patients with very early onset frontotemporal dementia (S39.007)

Clinical and genetic characteristics of patients with very early onset frontotemporal dementia (S39.007)

Very-Early Onset Chronic Active Colitis with Heterozygous Variants in LRBA1 and CARD11, a Case of “Immune TOR-Opathies”

Background A small subset of cases of inflammatory bowel disease (IBD) occurs as a result of single gene defects, and typically occurs in young or very young pediatric patients, referred to as “monogenic very-early onset IBD (VEO-IBD)”. The gene variants leading to monogenic VEO-IBD are often associated with primary immunodeficiency syndromes. Case report A six year-old girl presented to our gastroenterology clinic with LRBA deficiency with a heterozygous mutation at c.1399 A > G, p Met467Val, histopathologic chronic active colitis without granulomas and clinical chronic colitis. Her gastrointestinal symptoms began at age 5 with bloody diarrhea, abdominal pain and weight loss. Whole exome sequencing revealed a CARD11 heterozygous de novo mutation (c.220 + 1G > A). She was in clinical remission on only abatacept. Discussion We present a case of monogenic VEO-IBD associated with two heterozygous variants in LRBA1 and CARD11, both considered as key players in the newly proposed “immune TOR-opathies”.

Twenty-first Century Trends in the Global Epidemiology of Pediatric-Onset Inflammatory Bowel Disease: Systematic Review

The incidence of inflammatory bowel disease (IBD) is increasing internationally, particularly in nations with historically low rates. Previous reports of the epidemiology of pediatric-onset IBD identified a paucity of data. We systematically reviewed the global trends in incidence and prevalence of IBD diagnosed in individuals <21 years old over the first 2 decades of the 21st century. We systematically reviewed studies indexed in MEDLINE, EMBASE, Airiti Library, and SciELO from January 2010 to February 2020 to identify population-based studies reporting the incidence and/or prevalence of IBD, Crohn's disease, ulcerative colitis, and/or IBD-unclassified. Data from studies published before 2000 were derived from a previously published systematic review. We described the geographic distribution and trends in children of all ages and limiting to very early onset (VEO) IBD. A total of 131 studies from 48 countries were included. The incidence and prevalence of pediatric-onset IBD is highest in Northern Europe and North America and lowest in Southern Europe, Asia, and the Middle East. Among studies evaluating trends over time, most (31 of 37, 84%) studies reported significant increases in incidence and all (7 of 7) reported significant increases in prevalence. Data on the incidence and prevalence of VEO-IBD are limited to countries with historically high rates of IBD. Time trends in the incidence of VEO-IBD were visually heterogeneous. Rates of pediatric-onset IBD continue to rise around the world and data are emerging from regions where it was not previously reported; however, there remains a paucity of data on VEO-IBD and on pediatric IBD from developing and recently developed countries.

Biallelic inheritance of hypomorphic PKD1 variants is highly prevalent in very early onset polycystic kidney disease

To investigate the prevalence of biallelic PKD1 and PKD2 variants underlying very early onset (VEO) polycystic kidney disease (PKD) in a large international pediatric cohort referred for clinical indications over a 10-year period (2010-2020). All samples were tested by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA) of PKD1 and PKD2 genes and/or a next-generation sequencing panel of 15 additional cystic genes including PKHD1 and HNF1B. Two patients underwent exome or genome sequencing. Likely causative PKD1 or PKD2 variants were detected in 30 infants with PKD-VEO, 16 of whom presented in utero. Twenty-one of 30 (70%) had two variants with biallelic in trans inheritance confirmed in 16/21, 1 infant had biallelic PKD2 variants, and 2 infants had digenic PKD1/PKD2 variants. There was no known family history of ADPKD in 13 families (43%) and a de novo pathogenic variant was confirmed in 6 families (23%). We report a high prevalence of hypomorphic PKD1 variants and likely biallelic disease in infants presenting with PKD-VEO with major implications for reproductive counseling. The diagnostic interpretation and reporting of these variants however remains challenging using current American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) and Association of Clinical Genetic Science (ACGS) variant classification guidelines in PKD-VEO and other diseases affected by similar variants with incomplete penetrance.

A25 THE RISING GLOBAL INCIDENCE OF PEDIATRIC INFLAMMATORY BOWEL DISEASE: A SYSTEMATIC REVIEW OF POPULATION-BASED STUDIES

Abstract Background The incidence of inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), is increasing internationally, particularly in developing nations where rates were historically low. Previous reports of the incidence and prevalence of pediatric-onset IBD have identified a paucity of population-based studies. Aims We reviewed the global trends in incidence of pediatric IBD using evidence from population-based studies. Methods (PROSPERO CRD42019125193) We systematically reviewed studies indexed in MEDLINE, EMBASE, Airiti Library, and SciELO from 01/2010-02/2020 to identify population-based studies reporting the incidence of pediatric-onset IBD, CD, and UC. Included studies combined childhood and adolescent-onset IBD (onset &amp;lt;21y). Changes in incidence since 2000 were plotted by continent, with data from 2000–09 provided by our previous systematic review1. To depict trends, multiple times points reported in single studies were connected on graphs. When incidence was reported as an aggregated estimate over a range of years, data was plotted using the midpoint of the interval. Results Of 8096 abstracts screened, 74 studies described the incidence of IBD, CD, or UC in 33 countries (Figure panel A). The incidence of pediatric-onset IBD is highest in Northern Europe and North America, and lowest in Southern Europe, Asia, and the Middle East. This geographical distribution is similar in UC, while incidence of pediatric-onset CD is highest in North America and Northern Europe, followed by Australia. Trends in incidence over time, stratified by continent, are reported in Figure, panel B. Significantly increasing incidence of IBD, CD, and/or UC was reported in China, Bahrain, Canada, New Zealand, Australia, Singapore, Saudi Arabia, and most European countries. Very Early Onset (VEO) IBD significantly increased in Canada, however Saudi Arabia reported decreasing incidence of VEO-CD but stable incidence of VEO-UC. Conclusions Conclusion: Incidence of pediatric-onset IBD are highest in Northern Europe and North American and are increasing globally. There remains a paucity of studies from many parts of the world on the incidence pediatric IBD. Further research is needed to understand the pathogenesis of the rising incidence of pediatric IBD, including work to understand the genetic, environmental, immunological and microbiome alterations leading to the increasing rates in children.

COLORECTAL ADENOCARCINOMA DEVELOPING IN A YOUNG FEMALE WITH OVERLAP SYNDROME AND VERY EARLY ONSET-INFLAMMATORY BOWEL DISEASE: A CASE REPORT

We present a 4-year-old female diagnosed with very-early onset inflammatory bowel disease (VEO-IBD), ulcerative colitis type, and overlap syndrome based on clinical presentation, blood and stool studies, diagnostic endoscopies and liver biopsy. Her clinical course was complicated by pervasive psychological stressors, non-compliance with medical therapy, and frequent provider changes. Initial treatment included Prednisone, 6-mercaptopurine and Ursodiol. Treatment was escalated to include multiple biological agents which were stopped prematurely due to non-adherence.

COLORECTAL ADENOCARCINOMA DEVELOPING IN A YOUNG FEMALE WITH OVERLAP SYNDROME AND VERY EARLY ONSET-INFLAMMATORY BOWEL DISEASE: A CASE REPORT

Abstract We present a 4-year-old female diagnosed with very-early onset inflammatory bowel disease (VEO-IBD), ulcerative colitis type, and overlap syndrome based on clinical presentation, blood and stool studies, diagnostic endoscopies and liver biopsy. Her clinical course was complicated by pervasive psychological stressors, non-compliance with medical therapy, and frequent provider changes. Initial treatment included Prednisone, 6-mercaptopurine and Ursodiol. Treatment was escalated to include multiple biological agents which were stopped prematurely due to non-adherence. She developed weight loss and growth stunting, necessitating exclusive enteral nutrition and then parenteral nutrition. Due to medically refractory disease, she underwent a total colectomy with end ileostomy at the age of 13. Pathology revealed stage III colorectal adenocarcinoma (CRC) with lymph node involvement and transmural inflammation diagnostic of Crohn’s disease (CD). Genetic testing of the resected colon noted a missense mutation of TP53. Our patient completed 6 cycles of extensive and targeted chemotherapy with no evidence of disease reccurrence. She recently underwent ileal pouch-anal anastomosis and creation of a diverting ileostomy. CRC is exceedingly rare in pediatric IBD (PIBD) patients, with less than 30 reported cases in the available literature1. Most cases occurred in males and patients with ulcerative colitis (UC) and primary sclerosing cholangitis (PSC), where the risk of developing CRC is four times greater2. The risk of CRC increases with disease duration, with most PIBD patients developing CRC at 25 years of age1. Interestingly, mutations in TP53, a tumour suppressor gene, have been found to occur more frequently in patients with IBD-CRC compared to those with sporadic-CRC or IBD without dysplasia3. Mutations in TP53 may not only increase a patients general susceptibility to CRC but may also accelerate its development by contributing to excessive inflammation4. Our patient’s treatment refractory clinical course and transition in IBD diagnosis from UC to CD highlights the complexity of VEO-IBD management. While rare in pediatric patients, the development of CRC is a life-threatening risk and it should be considered in patients with prolonged and severely refractory IBD with concomitant autoimmune liver disease. Our patient’s young age at the time of CRC diagnosis emphasizes the need for vigilant yearly endoscopic screening and development of pediatric guidelines for dysplasia monitoring in this high risk population. Further research is needed to evaluate the role of genetic variant screening in CRC risk stratification.

The Efficacy of Risperidone on the Treatment of Very-Early Onset Skin Picking Disorder

Skin picking disorder (SPD) has frequently been reported to start before the age of 10; but “very-early onset” type was not defined before in the literature. Also research on the treatment of SPD in childhood is limited. We presented a “very-early onset” SPD case whose symptoms have started on the age of 4 and escalated with her comorbid oppositional defiant disorder diagnosis. Patient was successfully treated with low dose (0.25 mg/day) risperidone and proper psychoeducational interventions. Identifying SPD in very early childhood is hard cause; criterion of SPD might not capture all the specific features which very young children manifest and clinicians might overlook their complaints. Efficacy of risperidone might reflect a shared psychopathological etiology between impulse control and SPD, and lead future research on treatment of SPD with atypical anti-psychotics.

Colonoids From Patients With Pediatric Inflammatory Bowel Disease Exhibit Decreased Growth Associated With Inflammation Severity and Durable Upregulation of Antigen Presentation Genes.

Defining epithelial cell contributions to inflammatory bowel disease (IBD) is essential for the development of much needed therapies for barrier repair. Children with very early onset (VEO)-IBD have more extensive, severe, and refractory disease than older children and adults with IBD and, in some cases, have defective barrier function. We therefore evaluated functional and transcriptomic differences between pediatric IBD (VEO and older onset) and non-IBD epithelium using 3-dimensional, biopsy-derived organoids. We measured growth efficiency relative to histopathological and clinical parameters in patient enteroid (ileum) and colonoid (colon) lines. We performed RNA-sequencing on patient colonoids and subsequent flow cytometry after multiple passages to evaluate changes that persisted in culture. Enteroids and colonoids from pediatric patients with IBD exhibited decreased growth associated with histological inflammation compared with non-IBD controls. We observed increased LYZ expression in colonoids from pediatric IBD patients, which has been reported previously in adult patients with IBD. We also observed upregulation of antigen presentation genes HLA-DRB1 and HLA-DRA, which persisted after prolonged passaging in patients with pediatric IBD. We present the first functional evaluation of enteroids and colonoids from patients with VEO-IBD and older onset pediatric IBD, a subset of which exhibits poor growth. Enhanced, persistent epithelial antigen presentation gene expression in patient colonoids supports the notion that epithelial cell-intrinsic differences may contribute to IBD pathogenesis.

P0057ADPKD: COMPLEX GENOTYPES MAY EXPLAIN SEVERE PHENOTYPE AND INTRAFAMILIAL PHENOTYPIC VARIABILITY

Abstract Background and Aims Discordant affected relative-pairs are seen in ∼10% of families with Autosomal Dominant Polycystic Kidney Disease (ADPKD); &amp;lt;1% of patients exhibit very early onset (VEO) disease. Complex genotypes may result in renal disease variability beyond that predicted by the sole effect of a single PKD mutant allele, leading to the discovery of biallelic or digenic disease. Here we illustrate such complexity in 6 ADPKD pedigrees. Method Among our single-center ADPKD cohort (186 index patients), we selected pedigrees (P) in which marked familial phenotypic variability or severe and early onset disease was investigated by NGS and MLPA analysis of PKD1 and PKD2 genes and NGS analysis of other cystogenes. Segregation analysis by Sanger sequencing of PKD variants was performed in available affected and unaffected family members. Results In P1 and P2, the index cases (IC), presented with very early onset (VEO) disease characterized by prenatal/neonatal enlarged and hyperechogenic kidneys mimicking autosomal recessive polycystic kidney disease (ARPKD). In P1, with neonatal onset, the ADPKD affected father transmitted a PKD1 PT variant p.Gln4231*, whereas the mother, without renal cystic phenotype, transmitted a PKD1 hypomorphic variant p.Asp1332Asn. In P2, the ADPKD-PKD2 mother’s pregnancy was complicated by Potter sequence. Parent’s PKHD1 gene analysis was negative. Two missense NT variants in PKD1/PKD2 genes were detected in the healthy father, respectively p.Gly1944Arg and p.Thr203Ile. Therefore, a complex PKD inheritance was supposed in the fetus. Fetus DNA was not available. In P3 early onset (EO) ADPKD in two monozygous twins was underpinned by a PKD1 NT variant (p.Arg1951Gln) inherited by the ADPKD mild affected father and worsened by a de novo PKD1 truncating variant p.Arg2402*. In P4 and P5 a digenic ADPKD (PKD1 +PKD2 and PKD1 +PKHD1) was diagnosed in severe ADPKD IC. In P4 the two most severely affected siblings carried a PKD2 T variant (p.Ala365fs) and a PKD1 NT variant p-Cys259Tyr. In P5 the IC presented with EO ADPKD, a de novo splicing variant c.2097 + 5_+6insT in PKD1 gene was discovered but the phenotype was probably worsened by the presence of biallelic variant in a second cystogene PKHD1: one paternally inherited: p.Gly1712Arg and one maternally inherited: p.Asp3088Asn . Elderly parents in P6 had mild ADPKD with bilateral few kidney cysts and preserved eGFR, whereas IC showed moderate/severe CKD due to ADPKD biallelic variants. The IC carried a homozygous PKD1 NT variant (p.Arg4154Cys): each mutant allele inherited from the mild ADPKD affected parents. Conclusion Our study illustrates the genetic complexity in an otherwise “simple” Mendelian disorder, providing insights into the genetic basis of severity of ADPKD cases and into ADPKD intrafamilial disease variability. In our pedigree all cases with more severe clinical picture in the family presented at least two PKD variants. In P5 we found for the first time an EO ADPKD due to both PKD1 and PKHD1 variants. PKD1 and PKD2 sequence analysis together with cystic kidney disease gene panel analysis is recommended in those patients with discordant phenotype compared to family members. Molecular study of PKD patients is expected to be a good prognostic tool together with clinical and renal imaging data to better manage disease therapy, follow-up and reproductive issues.

P1799GENOTYPE-PHENOTYPE CORRELATION IN A PEDIATRIC ADPKD COHORT

Abstract Background and Aims The correlation between genotype and phenotype is well described in ADPKD adults. PKD2 is milder than PKD1 disease, with end stage kidney disease (ESKD) occurring on average 20 years later, and patients with PKD1 truncating mutations having a more severe outcome than PKD1 non-truncating mutations. Still, large differences in outcome occur even within families carrying the same gene variation. Only a few cases series reported the genetic profile of severely affected ADPKD children and suggest an additional effect of hypomorphic genes. We therefore aim to analyse the geno-phenotype profile in a well characterized pediatric ADPKD cohort. Method Clinical, familial, biological and imaging data were collected longitudinally in children diagnosed with ADPKD. Genotypic analysis was done using a custom Agilent SureSelect gene panel containing 136 ciliopathy-associated genes, including PKD1 and PKD2. Mutations and/or variants identified were individually evaluated for pathogenicity. Results 57 ADPKD children from 44 families were diagnosed at a mean (± SD) age of 4.1 (±4.8) years. ADPKD diagnosis was made in 32 children (56%) because of asymptomatic screening as requested by the family; 7 (12%) due to presenting symptoms (6 due to urinary tract infection and 1 due to post-traumatic macroscopic hematuria); 9 (16%) due to a coincidental finding of renal cysts on US performed for another reason and in 9 cases (16%) a prenatal diagnosis was performed. Twenty-nine children (51%) met the definition of very-early onset (VEO) disease. We identified pathogenic mutations in 100% of our patients, in which the prevalence of PKD1 truncating, PKD1 non-truncating, PKD2 and GANAB mutations was 75%, 19%, 4%, and 2%, respectively. Four cases (7%) were due to a de novo mutation. Interestingly, in 29 patients (51%) the germline mutation was the only identified mutation. However, in the rest of the subjects additional variants were identified in other ciliopathy-associated genes. In 12 cases (21%) the additional identified variants found in either the PKD, PMM2, HNF1B, DNAJC1, CEP290, NEK1, MKKS, NPHP4 or PKHD1 genes were scored to have a potential phenotypic effect, which will be evaluated by continued follow-up of this cohort. Conclusion We report the first large cohort of genotyped ADPKD children, including an extensive panel of ciliopathy genes next to the PKD genes. Interestingly, we found a high prevalence of additional and potentially modifying variants in this young population.

Clinical and genetic features of glomerulocystic kidney in childhood

The review provides historical information on the study of renal cystosis that occurs with glomerular cysts, discusses terminology issues and classification of diseases that occur with glomerulocystic kidney. The course features, diagnostic methods, treatment, and prognosis of renal glomerulocystosis in children, renal and extrarenal manifestations of two subtypes of hereditary glomerulocystic kidney disease: autosomal dominant glomerulocystic kidney disease associated with mutations of uromodulin (OMIM 609886) and familial hypoplastic glomerulocystic kidney disease associated with mutations of the HNF-1β (TCF2) gene (OMIM 137920). Diagnostic tetrad of familial hypoplastic glomerulocystic kidney disease, features of course and prognosis of HNF-1β-associated kidney disease with very early onset (VEO), MODY5 diabetes caused by HNF-1β mutation and 17q12 microdeletion syndrome in children were detected. According to the results of ultrasound examination (US), the fetus and newborn reveal hyperechogenicity of the kidney parenchyma, the volume of which is increased or corresponds to normal values. Renal cysts in glomerulocystic kidney are small, located in the cortical layer or subcapsularly, single or multiple, rarely diagnosed in the neonatal period. In young children, US shows a picture of increasing hyperechogenicity of the parenchyma with visualization of renal cysts in the cortical layer or subcapsularly, a decrease in the volume or asymmetry in the size of the kidneys. Urinary syndrome in glomerulocystic kidney in childhood is characterized by hematuria, microproteinuria, magniuria and uraturia in combination with hypostenuria and polyuria. Molecular genetic research reveals the mutation of genes responsible for the development of inherited diseases that occur with glomerulocystic kidney, and largely determines the prognosis and management tactics of the patient. A systematic approach is needed in the diagnosis and treatment of glomerulocystic kidney in children in order to slow the progression of chronic kidney disease and extrarenal manifestations, and to maintain continuity of observation of patients in pediatric and adult nephrological structures.

2518 Transitory Hemophagocytic Lymphohistiocytosis (HLH)/Macrophage Activation Syndrome (MAS) in a Child With Very Early Onset (VEO) of Ulcerative Colitis (UC) Complicated With Primary Sclerosing Cholangitis (PSC)

INTRODUCTION: VEO - Inflammatory bowel disease (IBD), in children younger than 6 years of age, is frequently associated with a more severe course and distinct genetic profile compared with later onset IBD. We report the case of a child with VEO - UC complicated with PSC and HLH/MAS. CASE DESCRIPTION/METHODS: A 10-year-old male, presented with bloody diarrhea, hepatomegaly and elevated transaminases when he was 30 months old. He had moderate pancolitis associated with C difficile (Cdiff) infection. He improved after metronidazole and sulfasalazine (SFZ) treatment. Two months later, he had hematochezia and endoscopic worsening of his colitis, which improved after discontinuing SFZ and receiving steroids and 6-MP. MRCP was consistent with PSC (Figure 1) and he was started on ursodiol. At ∼ 7 years of age, while receiving treatment with 6MP and Infliximab, he was hospitalized due to fever, hepatomegaly, diarrhea and pancytopenia. Blood and stool cultures, and tests for Cdiff, EBV, CMV, rota and parvovirus were negative. Triglyceride and ferritin levels were normal. He improved clinically and his pancytopenia resolved after 5 days of empirical antibiotic treatment (AbTx). Bone marrow biopsy (BMBx) was deferred. Metabolites of 6MP were normal but 6MP was held temporarily. Six months later, he had fever and diarrhea associated with pancytopenia and high levels of ESR, CRP, ferritin, triglyceride and interleukin 2 receptor. Number and function of NK cells were decreased. Stools and blood cultures, and tests for EBV, HSV and CMV were negative. Cdiff stool antigen was positive but PCR was negative. BMBx showed histiocytosis and erythophagocytosis (Figure 2). Lymphocyte flow cytometry was negative for lymphoproliferative disorder. After AbTx he improved and pancytopenia and ferritin level corrected within one week. Routine immunodeficiency tests were normal. Gene mutations associated with familial HLH: PRF1, Rab27A, SH2D1A, STX11, STXBP2, UNC 13D and XIAP were negative. 6MP was held. Infliximab initially, and subsequently Adalimubab, were discontinued because of high antibodies and allergic reactions. Five months later 6MP was restarted. He has been in remission of UC for 16 months. DISCUSSION: HLH/MAS is a very rare, potentially fatal complication in IBD patients. Our patient has a history of VEO - UC, PSC and two episodes of pancytopenia not associated with EBV or CMV - one of which fulfilled criteria for HLH/MAS. Remarkably, he recovered within one week after empirical AbTx without steroids or other treatment for HLH/MAS.

312 Patients With Very Early Onset Colorectal Cancer Have Increased Microsatellite Instability

INTRODUCTION: The incidence of colorectal cancer (CRC) in young patients has been increasing. This has led to increase interest in the molecular patterns and epigenetics of CRC in this age group. Microsatellite instability has been noted to be a positive prognostic factor in CRC. We aimed to evaluate the disease and molecular characteristics of patients with early-onset CRC (40-49 years of age) and compare them with those of very early-onset CRC (&lt;40 years of age). METHODS: A retrospective cross-sectional study was performed using our electronic pathology database. All patients diagnosed with CRC between January 2012 and September 2018 were included. Data regarding patient demographics, comorbid conditions and patient presentation was noted. We also noted information regarding the location, staging and molecular features of CRC. RESULTS: A total of 627 patients with CRC were identified. Out of these, 117 (18.6%) were younger than 50 years of age (early-onset CRC). From patients &lt; 50 years of age, 74 (63.2%) had early-onset CRC (40-49 years of age) and 36.8% of patients had very early-onset (&lt;40 years of age). The mean age was 45.4 in those between 40-49 years of age and 33.5 in those &lt; 40 years of age. The most common complaint in early-onset CRC was rectal bleeding (44.6%), while abdominal pain was the most common (39.5%) complaint in the very-early onset CRC group. There were no differences in stage of CRC among both groups. Microsatellite instability (MSI) was more common in patients with very early-onset CRC (40.7 vs 13.6%, P-value = 0.009) as compared to those with early onset CRC. Other clinical and molecular features of patients with very-early onset CRC are summarized in Table 1. CONCLUSION: There are unique clinical characteristics and molecular features in patients with very-early onset CRC. Our study shows that patients very early-onset CRC have increased MSI. Although our study limitations include a small sample size and an experience from a single center, our findings suggest that further understanding of molecular features in patients with very early-onset CRC is needed to improve diagnosis and management of CRC in this age group.

Maternal Haplotypes in DHFR Promoter and MTHFR Gene in Tuning Childhood Acute Lymphoblastic Leukemia Onset-Latency: Genetic/Epigenetic Mother/Child Dyad Study (GEMCDS)

Childhood acute lymphoblastic leukemia (ALL) peaks around age 2–4, and in utero genetic epigenetic mother-fetus crosstalk might tune ALL onset during childhood life. Folate genes variably interact with vitamin status on ALL risk and prognosis. We investigated DHFR and MTHFR gene variants in 235 ALL children and their mothers to disclose their role in determining ALL onset age and survival. Pyrosequence of DHFR 19bp ins/del (rs70991108; W/D), MTHFR C677T (rs1801133; C>T), and MTHFR A1298C (rs1801131; A>C) was assessed in children and in 72% of mothers for dyad-analysis comparison. DHFR DD-children had delayed ALL onset compared to WW-children (7.5 ± 4.8 vs. 5.2 ± 3.7 years; P = 0.002) as well as MTHFR 1298 CC-children compared to AA-children (8.03 ± 4.8 vs. 5.78 ± 4.1 years; P = 0.006), and according to the strong linkage disequilibrium between MTHFR 677 T-allele and 1298C-allele, MTHFR TT-children showed early mean age of onset though not significant. Offspring of MTHFR 677 TT-mothers had earlier ALL onset compared to offspring of 677 CC-mothers (5.4 ± 3.3 vs. 7 ± 5.3 years; P = 0.017). DHFR/MTHFR 677 polymorphism combination influenced onset age by comparing DD/CC vs. WW/TT children (8.1 ± 5.7 vs. 4.7 ± 2.1 years; P = 0.017). Moreover, mother-child genotype combination gave 5.5-years delayed onset age in favor of DD-offspring of 677 CC-mothers vs. WW-offspring of 677 TT-mothers, and it was further confirmed including any D-carrier children and any 677 T-carrier mothers (P = 0.00052). Correction for multiple comparisons maintained statistical significance for DHFR ins/del and MTHFR A1298C polymorphisms. Unexpectedly, among the very-early onset group (<2.89 years; 25th), DD-genotype inversely clustered in children and mothers (4.8% vs. 23.8% respectively), and accordingly ALL offspring of homozygous DD-mothers had increased risk to have early-onset (adjusted OR (odds ratio) = 3.08; 1.1–8.6; P = 0.03). The opposite effect DHFR promoter variant has in tuning ALL onset-time depending on who is the carrier (i.e., mother or child) might suggest a parent-origin-effect of the D-allele or a two-faced epigenetic role driven by unbalanced folate isoform availability during the in-utero leukemogenesis responsible for the wide postnatal childhood ALL latency.

SAT-334 GENETIC TESTING OF FAMILIES WITH VERY EARLY ONSET POLYCYSTIC KIDNEY DISEASE REVEALS THE FUNCTIONAL SIGNIFICANCE OF HYPOMORPHIC VARIANTS

Autosomal dominant polycystic kidney disease (ADPKD) is generally an adult onset disorder; however rare very early onset (VEO) cases under the age of 2 years are reported and have a high recurrence risk in subsequent pregnancies. Elucidation of the underlying mechanism causing the early onset phenotype has significant benefits for genetic and reproductive counselling. We performed an audit of all ADPKD diagnostic referrals with age of onset less than 2 years referred for diagnostic genetic testing of PKD1 and PKD2 from 2010-2018. Testing was performed by long-range PCR with Sanger sequencing of all coding exons and/or next-generation sequencing (from 2016 onwards) and MLPA. A total of 28 cases with reported age of disease onset under 2 years were identified. 5 patients with a clinical history not suggestive of ADPKD and no mutation detected in PKD1 and PKD2 were subsequently excluded. Of the remaining 23 patients, 15 (65%) had at least 2 variants detected, including one likely hypomorphic variant; 4 (22%) had one pathogenic PKD1 mutation and 3 (13%) had no mutation detected in PKD1 or PKD2. Parental analysis from 12 families confirmed biallelic inheritance in 9 (75%) cases and 4 (33%) cases with a de novo mutation. Bilineal inheritance of PKD1 and PKD2 variants was found in 2 cases and biallelic PKD2 mutations in 1 case. Of the 15 patients with multiple variants, 13 had a likely or definitely pathogenic mutation as well as a likely hypomorphic variant; whilst 2 patients had 2 likely hypomorphic variants confirmed in trans. 10 (43%) cases had no previous family history of ADPKD. This study highlights a high incidence of hypomorphic variants inherited in trans with a pathogenic mutation or another hypomorphic variant in children with a VEO phenotype. The previously reported and experimentally validated p.(Arg3277Cys) hypomorphic PKD1 variant was detected in 3 families. The minor allele frequency of the hypomorphic variants detected ranged from 0-0.2% which is higher than expected for a disease-causing variant. These variants require careful consideration in the context of early onset disease and parental segregation analysis to determine phase. Our study also demonstrates a high incidence of de novo mutations and high incidence of cases with no previous family history. A model of reduced gene dosage during embryonic kidney maturation is the simplest molecular mechanism underlying the VEO phenotype.