Non-coding variants disrupting a tissue-specific regulatory element in HK1 cause congenital hyperinsulinism.

Gene expression is tightly regulated, with many genes exhibiting cell-specific silencing when their protein product would disrupt normal cellular function1. This silencing is largely controlled by non-coding elements, and their disruption might cause human disease2. We performed gene-agnostic screening of the non-coding regions to discover new molecular causes of congenital hyperinsulinism. This identified 14 non-coding de novo variants affecting a 42-bp conserved region encompassed by a regulatory element in intron 2 of the hexokinase 1 gene (HK1). HK1 is widely expressed across all tissues except in the liver and pancreatic beta cells and is thus termed a 'disallowed gene' in these specific tissues. We demonstrated that the variants result in a loss of repression of HK1 in pancreatic beta cells, thereby causing insulin secretion and congenital hyperinsulinism. Using epigenomic data accessed from public repositories, we demonstrated that these variants reside within a regulatory region that we determine to be critical for cell-specific silencing. Importantly, this has revealed a disease mechanism for non-coding variants that cause inappropriate expression of a disallowed gene.

Embryonal sarcoma of the liver in a girl with Cockayne syndrome.

The first reported malignancy associated with Cockayne syndrome.

Management and outcome of paediatric testicular tumours - A 20 year experience.

OBJECTIVE: To report a 20-year experience highlighting management and outcome(s) of paediatric testicular tumours. PATIENTS AND METHODS: All males (< 19 years) with an index diagnosis of testicular tumours during the era(s) 1998-2018 in North West England were identified. Data were collected regarding age at diagnosis, disease stage, surgical operations, tumour biology and outcome(s). RESULTS: A total of 34 male patients were identified. Median age at primary diagnosis was 94 months (range: 0-229 months). Eighteen tumours were benign and 16 malignant. Twenty cases (59%) were recorded in pre pubertal children and 14 (41%) in post pubertal males . In the pre pubertal group (0-11 years) - 15 cases of germ cell tumours (unrelated to germ cell neoplasia in situ - non-GCNIS derived) were recorded, including six yolk sac lesions, eight teratomas and one mixed teratoma/yolk sac tumour (pre-pubertal type). Four males with sex cord-stromal tumours included one juvenile granulosa cell tumour, two Sertoli cell tumours and one Leydig cell tumour. One miscellaneous type tumour notably a papillary cyst adenoma was also identified. In the post pubertal male cohort (>12 years) (n = 14) - four non-GCNIS derived tumours were identified (3 epidermoid cysts and one teratoma), eight cases of germ cell tumour derived from germ cell neoplasia in situ (GCNIS derived) included one teratoma, six with mixed germ cell tumours and one embryonal carcinoma. Two males had sex cord stromal tumours: (Leydig cell and granulosa cell biology). Twenty-eight patients underwent high radical inguinal orchidectomy(s) with one male also requiring retroperitoneal surgery to clear distant locoregional disease and a further single case thoracotomy and metastasectomy. Six patients had lesions suitable for 'testicular sparing' surgery. Six patients had metastatic disease at presentation (18%). Overall study survival was 97%. A single fatality occurred in an adolescent male with a mixed GCT harbouring liver, lung and para-aortic disease who died 48 months after initiating treatment. CONCLUSION: We highlight one of the largest study series of paediatric testicular tumours in the UK and Europe. Non-GCNIS derived tumours accounted for the most common tumour biology (56%). Survival for paediatric testicular tumours is reassuringly generally excellent. Delayed presentation however with a malignant testicular tumour may be associated with poor outcome(s).

Neutrophil dysfunction triggers inflammatory bowel disease in G6PC3 deficiency.

The glucose-6-phosphatase catalytic subunit 3 (G6PC3) encodes a ubiquitously expressed enzyme that regulates cytoplasmic glucose availability. Loss-of-function biallelic G6PC3 mutations cause severe congenital neutropenia and a diverse spectrum of extra-hematological manifestations, among which inflammatory bowel disease (IBD) has been anecdotally reported. Neutrophil function and clinical response to granulocyte colony-stimulating factor (G-CSF) and hematopoietic stem cell transplantation (HSCT) were investigated in 4 children with G6PC3 deficiency-associated IBD. G6PC3 deficiency was associated with early-onset IBD refractory to treatment with steroids and infliximab. The symptoms of IBD progressed despite G-CSF treatment. In vitro studies on the patients' blood showed that neutrophils displayed higher levels of activation markers (CD11b, CD66b, and CD14), excessive IL-8 and reactive oxygen species, and increased apoptosis and secondary necrosis. Secondary necrosis was exaggerated after stimulation with Escherichia coli and could be partially rescued with supplemental exogenous glucose. HSCT led to normalization of neutrophil function and remission of gastrointestinal symptoms. We conclude that neutrophils in G6PC3 deficiency release pro-inflammatory mediators when exposed to gut bacteria, associated with intestinal inflammation, despite treatment with G-CSF. HSCT is an effective therapeutic option in patients with G6PC3 deficiency-associated IBD refractory to immune suppressants.

Refractory very early-onset inflammatory bowel disease associated with cytosolic isoleucyl-tRNA synthetase deficiency: A case report.

BACKGROUND: Aminoacyl tRNA synthetases/ligases (ARSs) are highly conserved enzymes involved in attaching amino acids to tRNA promoting protein synthesis. Although deficiencies of ARSs localized to the mitochondria classically present with neuropathology, the clinical features of cytosolic ARS deficiencies are more variable. They have previously been associated with neonatal hepatitis, but never with early-onset inflammatory bowel disease. CASE SUMMARY: A nine-year-old Bangladeshi boy presented with neonatal liver failure and deranged clotting, transaminitis and cholestasis. His parents were first cousins. Two older brothers and a sister were well. The patient suffered from loose stools from early infancy which became more troublesome and persistent from five years old with ten bloody motions a day. Repeated endoscopies showed persistent pancolitis, which was refractory to mesalazine, corticosteroids, azathioprine, sirolimus and anti-TNF (adalimumab) therapy, but has improved recently with subcutaneous methotrexate.Whole Genome Sequencing revealed a novel pathogenic missense variant (c.290A > G) in the cytosolic isoleucyl-tRNA synthetase gene, leading to an amino acid substitution (p.Asp97Gly). Pathogenic variants in other genes associated with inflammatory bowel disease (IBD) (ADAM17, EGFR, FOXP3, IL10RA, IL10RB, IL21R, NCF4, STAT3) were excluded. Cytokine assays demonstrated markedly elevated IL-2, IL-5, IL-13, IL-9 and IL-10 by the patient's CD4+ T-cells, while IL-17A, IL-17F, IFNß were lower, and TNFα not significantly different when compared to healthy controls. CONCLUSION: This case report provides evidence that recessive mutations in cytosolic isoleucyl-tRNA synthetase are a novel monogenic cause of IBD, which should be considered, particularly in infants and children with a history of neonatal hepatitis and very early-onset IBD poorly responsive to treatment.

Isomorphic diffuse glioma is a morphologically and molecularly distinct tumour entity with recurrent gene fusions of MYBL1 or MYB and a benign disease course.

The "isomorphic subtype of diffuse astrocytoma" was identified histologically in 2004 as a supratentorial, highly differentiated glioma with low cellularity, low proliferation and focal diffuse brain infiltration. Patients typically had seizures since childhood and all were operated on as adults. To define the position of these lesions among brain tumours, we histologically, molecularly and clinically analysed 26 histologically prototypical isomorphic diffuse gliomas. Immunohistochemically, they were GFAP-positive, MAP2-, OLIG2- and CD34-negative, nuclear ATRX-expression was retained and proliferation was low. All 24 cases sequenced were IDH-wildtype. In cluster analyses of DNA methylation data, isomorphic diffuse gliomas formed a group clearly distinct from other glial/glio-neuronal brain tumours and normal hemispheric tissue, most closely related to paediatric MYB/MYBL1-altered diffuse astrocytomas and angiocentric gliomas. Half of the isomorphic diffuse gliomas had copy number alterations of MYBL1 or MYB (13/25, 52%). Gene fusions of MYBL1 or MYB with various gene partners were identified in 11/22 (50%) and were associated with an increased RNA-expression of the respective MYB-family gene. Integrating copy number alterations and available RNA sequencing data, 20/26 (77%) of isomorphic diffuse gliomas demonstrated MYBL1 (54%) or MYB (23%) alterations. Clinically, 89% of patients were seizure-free after surgery and all had a good outcome. In summary, we here define a distinct benign tumour class belonging to the family of MYB/MYBL1-altered gliomas. Isomorphic diffuse glioma occurs both in children and adults, has a concise morphology, frequent MYBL1 and MYB alterations and a specific DNA methylation profile. As an exclusively histological diagnosis may be very challenging and as paediatric MYB/MYBL1-altered diffuse astrocytomas may have the same gene fusions, we consider DNA methylation profiling very helpful for their identification.

Unravelling the genetic causes of mosaic islet morphology in congenital hyperinsulinism.

Congenital hyperinsulinism (CHI) causes dysregulated insulin secretion which can lead to life-threatening hypoglycaemia if not effectively managed. CHI can be sub-classified into three distinct groups: diffuse, focal and mosaic pancreatic disease. Whilst the underlying causes of diffuse and focal disease have been widely characterised, the genetic basis of mosaic pancreatic disease is not known. To gain new insights into the underlying disease processes of mosaic-CHI we studied the islet tissue histopathology derived from limited surgical resection from the tail of the pancreas in a patient with CHI. The underlying genetic aetiology was investigated using a combination of high depth next-generation sequencing, microsatellite analysis and p57kip2 immunostaining. Histopathology of the pancreatic tissue confirmed the presence of a defined area associated with marked islet hypertrophy and a cytoarchitecture distinct from focal CHI but compatible with mosaic CHI localised to a discrete region within the pancreas. Analysis of DNA extracted from the lesion identified a de novo mosaic ABCC8 mutation and mosaic paternal uniparental disomy which were not present in leukocyte DNA or the surrounding unaffected pancreatic tissue. This study provides the first description of two independent disease-causing somatic genetic events occurring within the pancreas of an individual with localised mosaic CHI. Our findings increase knowledge of the genetic causes of islet disease and provide further insights into the underlying developmental changes associated with ß-cell expansion in CHI.

Severe type I interferonopathy and unrestrained interferon signaling due to a homozygous germline mutation in STAT2.

Excessive type I interferon (IFNα/ß) activity is implicated in a spectrum of human disease, yet its direct role remains to be conclusively proven. We investigated two siblings with severe early-onset autoinflammatory disease and an elevated IFN signature. Whole-exome sequencing revealed a shared homozygous missense Arg148Trp variant in STAT2, a transcription factor that functions exclusively downstream of innate IFNs. Cells bearing STAT2R148W in homozygosity (but not heterozygosity) were hypersensitive to IFNα/ß, which manifest as prolonged Janus kinase-signal transducers and activators of transcription (STAT) signaling and transcriptional activation. We show that this gain of IFN activity results from the failure of mutant STAT2R148W to interact with ubiquitin-specific protease 18, a key STAT2-dependent negative regulator of IFNα/ß signaling. These observations reveal an essential in vivo function of STAT2 in the regulation of human IFNα/ß signaling, providing concrete evidence of the serious pathological consequences of unrestrained IFNα/ß activity and supporting efforts to target this pathway therapeutically in IFN-associated disease.

Utility of open surgical lung biopsy in children.

INTRODUCTION: Open lung biopsy (OLB) is commonly used to obtain a definitive histological diagnosis in children with respiratory disorders. This allows correct treatment pathways to be followed and guides discussions surrounding prognosis. Our aim was to determine if OLB is useful in obtaining a conclusive diagnosis in a child with complex respiratory disease. MATERIALS AND METHODS: In total, 179 OLB episodes were identified in children under 18 years from 2006 to 2016. Biopsies confirming congenital thoracic malformations or pulmonary metastatic disease were excluded. RESULTS: 42 patients had 44 episodes of OLB in the period studied. A definitive histological diagnosis was reached in 35 (79%) cases. There were no deaths directly attributable to OLB surgery. CONCLUSION: OLB contributed substantially in obtaining a definitive diagnosis for our patient population, no increase in mortality. It allowed targeted treatment and provided valuable prognostic information on the likely progression of the disease so families could plan for palliation where appropriate.

Intracranial Angiomatoid Fibrous Histiocytoma with EWSR1-CREB Family Fusions: A Report of 2 Pediatric Cases.

BACKGROUND: Intracranial angiomatoid fibrous histiocytomas (AFHs) are very rare tumors. Histologically, classical cases have been reported exclusively in adults, with myxoid variants identified only in children. Here, we report the clinical presentation, treatment, biopsy, and molecular test results for 2 children with classical intracranial AFH and combine this with a literature review of published intracranial AFH and AFH-like cases. CASE DESCRIPTION: Two young girls presenting with abnormal neurologic signs, received diagnoses of intracranial AFHs from histopathologic analysis. No myxoid features were identified. Fluorescence in situ hybridization and reverse transcriptase polymerase chain reaction testing demonstrated EWS1-ATF1 and EWS1-CREM gene fusions, respectively, verified by Sanger sequencing. Both patients underwent surgery only. The first child experienced local recurrence 5 years from initial surgery. Following a further complete resection, this patient has remained recurrence free over a subsequent 6-year follow-up period. The second patient has recently experienced local multinodular recurrence 28 months after initial surgery and is awaiting surgical re-excision. No additional chemotherapy/radiotherapy has been administered to either patient. CONCLUSIONS: This report describes the first 2 cases of nonmyxoid intracranial AFH in children; confirmed by molecular analysis. Our results suggest that a tumor spectrum incorporating classical and myxoid intracranial AFHs can occur in children and that gross total resection represents the treatment strategy of choice at diagnosis or following recurrence.

Clinical Diversity in Focal Congenital Hyperinsulinism in Infancy Correlates With Histological Heterogeneity of Islet Cell Lesions.

Background: Congenital Hyperinsulinism (CHI) is an important cause of severe and persistent hypoglycaemia in infancy and childhood. The focal form (CHI-F) of CHI can be potentially cured by pancreatic lesionectomy. While diagnostic characteristics of CHI-F pancreatic histopathology are well-recognized, correlation with clinical phenotype has not been established. Aims: We aimed to correlate the diversity in clinical profiles of patients with islet cell organization in CHI-F pancreatic tissue. Methods: Clinical datasets were obtained from 25 patients with CHI-F due to ABCC8/KCNJ11 mutations. 18F-DOPA PET-CT was used to localize focal lesions prior to surgery. Immunohistochemistry was used to support protein expression studies. Results: In 28% (n = 7) of patient tissues focal lesions were amorphous and projected into adjoining normal pancreatic tissue without clear delineation from normal tissue. In these cases, severe hypoglycaemia was detected within, on average, 2.8 ± 0.8 (range 1-7) days following birth. By contrast, in 72% (n = 18) of tissues focal lesions were encapsulated within a defined matrix capsule. In this group, the onset of severe hypoglycaemia was generally delayed; on average 46.6 ± 14.3 (range 1-180) days following birth. For patients with encapsulated lesions and later-onset hypoglycaemia, we found that surgical procedures were curative and less complex. Conclusion: CHI-F is associated with heterogeneity in the organization of focal lesions, which correlates well with clinical presentation and surgical outcomes.

Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.

Background: Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) is a negative immune regulator on the surface of T cells. In humans, heterozygous germline mutations in CTLA4 can cause an immune dysregulation syndrome. The phenotype comprises a broad spectrum of autoinflammatory, autoimmune, and immunodeficient features. An increased frequency of malignancies in primary immunodeficiencies is known, but their incidence in CTLA-4 insufficiency is unknown. Methods: Clinical manifestations and details of the clinical history were assessed in a worldwide cohort of 184 CTLA4 mutation carriers. Whenever a malignancy was reported, a malignancy-specific questionnaire was filled. Results: Among the 184 CTLA4 mutation carriers, 131 were considered affected, indicating a penetrance of 71.2%. We documented 17 malignancies, which amounts to a cancer prevalence of 12.9% in affected CTLA4 mutation carriers. There were ten lymphomas, five gastric cancers, one multiple myeloma, and one metastatic melanoma. Seven lymphomas and three gastric cancers were EBV-associated. Conclusion: Our findings demonstrate an elevated cancer risk for patients with CTLA-4 insufficiency. As more than half of the cancers were EBV-associated, the failure to control oncogenic viruses seems to be part of the CTLA-4-insufficient phenotype. Hence, lymphoproliferation and EBV viral load in blood should be carefully monitored, especially when immunosuppressing affected CTLA4 mutation carriers.

Atypical Forms of Congenital Hyperinsulinism in Infancy Are Associated With Mosaic Patterns of Immature Islet Cells.

Objectives: We aimed to characterize mosaic populations of pancreatic islet cells from patients with atypical congenital hyperinsulinism in infancy (CHI-A) and the expression profile of NKX2.2, a key transcription factor expressed in ß-cells but suppressed in δ-cells in the mature pancreas. Patients/Methods: Tissue was isolated from three patients with CHI-A following subtotal pancreatectomy. CHI-A was diagnosed on the basis of islet mosaicism and the absence of histopathological hallmarks of focal and diffuse CHI (CHI-D). Immunohistochemistry was used to identify and quantify the proportions of insulin-secreting ß-cells and somatostatin-secreting δ-cells in atypical islets, and results were compared with CHI-D (n = 3) and age-matched control tissues (n = 3). Results: In CHI-A tissue, islets had a heterogeneous profile. In resting/quiescent islets, identified by a condensed cytoplasm and nuclear crowding, ß-cells were reduced to <50% of the total cell numbers in n = 65/70 islets, whereas δ-cell numbers were increased with 85% of islets (n = 49/57) containing >20% δ-cells. In comparison, all islets in control tissue (n = 72) and 99% of CHI-D islets (n = 72) were composed of >50% ß-cells, and >20% δ-cells were found only in 12% of CHI-D (n = 8/66) and 5% of control islets (n = 3/60). Active islets in CHI-A tissue contained proportions of ß-cells and δ-cells similar to those of control and CHI-D islets. Finally, when compared with active islets, quiescent islets had a twofold higher prevalence of somatostatin/NKX2.2+ coexpressed cells. Conclusions: Marked increases in NKX2.2 expression combined with increased numbers of δ-cells strongly imply that an immature δ-cell profile contributed to the pathobiology of CHI-A.

Enhanced Islet Cell Nucleomegaly Defines Diffuse Congenital Hyperinsulinism in Infancy but Not Other Forms of the Disease.

OBJECTIVES: To quantify islet cell nucleomegaly in controls and tissues obtained from patients with congenital hyperinsulinism in infancy (CHI) and to examine the association of nucleomegaly with proliferation. METHODS: High-content analysis of histologic sections and serial block-face scanning electron microscopy were used to quantify nucleomegaly. RESULTS: Enlarged islet cell nuclear areas were 4.3-fold larger than unaffected nuclei, and the mean nuclear volume increased to approximately threefold. Nucleomegaly was a normal feature of pediatric islets and detected in the normal regions of the pancreas from patients with focal CHI. The incidence of nucleomegaly was highest in diffuse CHI (CHI-D), with more than 45% of islets containing two or more affected cells. While in CHI-D nucleomegaly was negatively correlated with cell proliferation, in all other cases, there was a positive correlation. CONCLUSIONS: Increased incidence of nucleomegaly is pathognomonic for CHI-D, but these cells are nonproliferative, suggesting a novel role in the pathobiology of this condition.

Successful Curative Therapy With Rituximab and Allogeneic Haematopoietic Stem Cell Transplantation for MALT Lymphoma Associated With STK4-Mutated CD4+ Lymphocytopenia.

Idiopathic CD4+ lymphocytopenia and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) are rare diseases in children. We report the first case of a child with STK4-mutated CD4+ lymphocytopenia who developed Epstein-Barr virus associated MALT lymphoma arising in the salivary gland. The child achieved complete remission with rituximab, and her immunodeficiency was cured by haematopoietic stem cell transplantation. The child remained well 24 months post transplantation.

Primary pleural precursor B-Cell lymphoblastic lymphoma.

Intrathoracic lymphoblastic lymphoma (LBL) is classically of T-cell lineage, but these cases of pleural B-cell LBL suggest that this is not always the case. Despite the clinical challenges involved every attempt should be made to secure a biopsy and histological diagnosis, as we move into an era of lineage-directed therapies.

Frequent Derepression of the Mesenchymal Transcription Factor Gene FOXC1 in Acute Myeloid Leukemia.

Through in silico and other analyses, we identified FOXC1 as expressed in at least 20% of human AML cases, but not in normal hematopoietic populations. FOXC1 expression in AML was almost exclusively associated with expression of the HOXA/B locus. Functional experiments demonstrated that FOXC1 contributes to a block in monocyte/macrophage differentiation and enhances clonogenic potential. In in vivo analyses, FOXC1 collaborates with HOXA9 to accelerate significantly the onset of symptomatic leukemia. A FOXC1-repressed gene set identified in murine leukemia exhibited quantitative repression in human AML in accordance with FOXC1 expression, and FOXC1(high) human AML cases exhibited reduced morphologic monocytic differentiation and inferior survival. Thus, FOXC1 is frequently derepressed to functional effect in human AML.

Germline mutations in SUFU cause Gorlin syndrome-associated childhood medulloblastoma and redefine the risk associated with PTCH1 mutations.

PURPOSE: Heterozygous germline PTCH1 mutations are causative of Gorlin syndrome (naevoid basal cell carcinoma), but detection rates > 70% have rarely been reported. We aimed to define the causative mutations in individuals with Gorlin syndrome without PTCH1 mutations. METHODS: We undertook exome sequencing on lymphocyte DNA from four unrelated individuals from families with Gorlin syndrome with no PTCH1 mutations found by Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), or RNA analysis. RESULTS: A germline heterozygous nonsense mutation in SUFU was identified in one of four exomes. Sanger sequencing of SUFU in 23 additional PTCH1-negative Gorlin syndrome families identified a SUFU mutation in a second family. Copy-number analysis of SUFU by MLPA revealed a large heterozygous deletion in a third family. All three SUFU-positive families fulfilled diagnostic criteria for Gorlin syndrome, although none had odontogenic jaw keratocysts. Each SUFU-positive family included a single case of medulloblastoma, whereas only two (1.7%) of 115 individuals with Gorlin syndrome and a PTCH1 mutation developed medulloblastoma. CONCLUSION: We demonstrate convincing evidence that SUFU mutations can cause classical Gorlin syndrome. Our study redefines the risk of medulloblastoma in Gorlin syndrome, dependent on the underlying causative gene. Previous reports have found a 5% risk of medulloblastoma in Gorlin syndrome. We found a < 2% risk in PTCH1 mutation-positive individuals, with a risk up to 20× higher in SUFU mutation-positive individuals. Our data suggest childhood brain magnetic resonance imaging surveillance is justified in SUFU-related, but not PTCH1-related, Gorlin syndrome.

SIADH and partial hypopituitarism in a patient with intravascular large B-cell lymphoma: a rare cause of a common presentation.

Hyponatraemia is a very common electrolyte abnormality with varied presenting features depending on the underlying cause. The authors report the case of a 75-year-old, previously fit, gentleman who presented with weight loss, lethargy and blackouts. He required four admissions to the hospital over an 8-month period. Investigations revealed persistent hyponatraemia consistent with a diagnosis of syndrome of inappropriate antidiuretic hormone secretion, macrocytic anaemia and partial hypopituitarism. Unfortunately, all other investigations that were performed failed to identify the underlying cause and a diagnosis of intravascular large B-cell lymphoma was only confirmed following postmortem studies. The authors recommend that endocrinologists should be involved at the outset in the management of patients with persistent hyponatraemia and that intravascular large B-cell lymphoma should be considered in the differential diagnosis of hyponatraemia.