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Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder characterized by intellectual disability, specific facial features, and marked autonomic nervous system dysfunction, especially with disturbances of regulating respiration and intestinal mobility. It is caused by variants in the transcription factor TCF4. Heterogeneity in the clinical and molecular diagnostic criteria and care practices has prompted a group of international experts to establish guidelines for diagnostics and care. For issues, for which there was limited information available in international literature, we collaborated with national support groups and the participants of a syndrome specific international conference to obtain further information. Here, we discuss the resultant consensus, including the clinical definition of PTHS and a molecular diagnostic pathway. Recommendations for managing particular health problems such as dysregulated respiration are provided. We emphasize the need for integration of care for physical and behavioral issues. The recommendations as presented here will need to be evaluated for improvements to allow for continued optimization of diagnostics and care.

With the clinical implementation of genomic microarrays, the detection of cryptic unbalanced rearrangements in patients with syndromic developmental delay has improved considerably. Here we report the molecular karyotyping and phenotypic description of six new unrelated patients with partially overlapping microdeletions at 10p12.31p11.21 ranging from 1.0 to 10.6 Mb. The smallest region of overlap is 306 kb, which includes WAC gene, known to be associated with microtubule function and to have a role in cell division. Another patient has previously been described with a 10Mb deletion, partially overlapping with our six patients. All seven patients have developmental delay and a majority of the patients have abnormal behaviour and dysmorphic features, including bulbous nasal tip, deep set eyes, synophrys/thick eyebrows and full cheeks, whereas other features varied. All patients also displayed various visual impairments and six out of seven patients had cardiac malformations. Taken together with the previously reported patient, our study suggests that the detected deletions may represent a new contiguous gene syndrome caused by dosage-sensitive genes that predispose to developmental delay.

Although the most common mechanism underlying congenital hyperinsulinism is dysfunction of the pancreatic ATP-sensitive potassium channel, the pathogenesis and genetic origins of this disease remains largely unexplained in more than half of all patients. UCP2 knockout mice exhibit an hyperinsulinemic hypoglycemia, suggesting an involment of UCP2 in insulin secretion. However, a possible pathogenic role for UCP2 protein in the development of human congenital hyperinsulinism or of any human disease has not yet been investigated. We studied ten children exhibiting congenital hyperinsulinism, without detectable mutations in the known congenital hyperinsulinism-causing genes. Parental-inherited heterozygous UCP2 variants encoding amino-acid changes were found in two unrelated children with congenital hyperinsulinism. Functional assays in yeast and in insulin-secreting cells revealed an impaired activity of UCP2 mutants. Therefore, we report the finding of UCP2 coding variants in human congenital hyperinsulinism, which reveals a role for this gene in the regulation of insulin secretion and glucose metabolism in humans. Our results show for the first time a direct association between UCP2 amino acid alteration and human disease and highlight a role for mitochondria in hormone secretion

Congenital hyperinsulinism (CHI), characterized by profound hypoglycaemia related to inappropriate insulin secretion, may be associated histologically with either diffuse insulin hypersecretion or focal adenomatous hyperplasia, which share a similar clinical presentation, but result from different molecular mechanisms. Whereas diffuse CHI is of autosomal recessive, or less frequently of autosomal dominant, inheritance, focal CHI is sporadic. The most common mechanism underlying CHI is dysfunction of the pancreatic ATP-sensitive potassium channel (K(+)(ATP)). The two subunits of the K(+)(ATP) channel are encoded by the sulfonylurea receptor gene (SUR1 or ABCC8) and the inward-rectifying potassium channel gene (KIR6.2 or KCNJ11), both located in the 11p15.1 region. Germ-line, paternally inherited, mutations of the SUR1 or KIR6.2 genes, together with somatic maternal haplo-insufficiency for 11p15.5, were shown to result in focal CHI. Diffuse CHI results from germ-line mutations in the SUR1 or KIR6.2 genes, but also from mutations in several other genes, namely glutamate dehydrogenase (with associated hyperammonaemia), glucokinase, short-chain L-3-hydroxyacyl-CoA dehydrogenase, and insulin receptor gene. Hyperinsulinaemic hypoglycaemia may be observed in several overlapping syndromes, such as Beckwith-Wiedemann syndrome (BWS), Perlman syndrome, and, more rarely, Sotos syndrome. Mosaic genome-wide paternal isodisomy has recently been reported in patients with clinical signs of BWS and CHI. The primary causes of CHI are genetically heterogeneous and have not yet been completely unveiled. However, secondary causes of hyperinsulinism have to be considered such as fatty acid oxidation deficiency, congenital disorders of glycosylation and factitious hypoglycaemia secondary to Munchausen by proxy syndrome.

CONTEXT: Congenital hyperinsulinism (HI) is characterized by hypoglycemia related to inappropriate insulin secretion. Focal and diffuse forms of hyperinsulinism share a similar clinical presentation, but their treatment is dramatically different. Preoperative differential diagnosis was based on pancreatic venous sampling, a technically demanding technique. OBJECTIVE: Positron emission tomography (PET) after injection of [18F]fluoro-L-DOPA (L-dihydroxyphenylalanine) has been evaluated for the preoperative differentiation between focal and diffuse HI, by imaging uptake of radiotracer and the conversion of [18F]fluoro-L-dopa into dopamine by DOPA decarboxylase. We propose to validate this test by immunohistochemical approach. PATIENTS AND METHODS: Pancreatic surgical specimens of four focal and three diffuse HI were studied, using anti-DOPA decarboxylase and proinsulin antibodies. The effect of an inhibitor of DOPA decarboxylase (carbidopa) on insulin secretion was evaluated in vivo and in cultured INS-1 cells. RESULTS: Immunohistochemical detection of DOPA decarboxylase showed diffuse staining of Langerhans islets in the whole pancreas in all diffuse cases, in contrast with dense focal staining in all focal cases. Staining of Langerhans islets outside the focal lesion was diffusely but weakly positive. We correlated the localization of DOPA decarboxylase and proinsulin in normal pancreas and in both diffuse and focal HI tissues. The diffuse PET uptake found before treatment in one child with diffuse HI disappeared completely after carbidopa administration, suggesting in vivo that pancreatic cells can take up amine precursors and contain DOPA decarboxylase. The insulin secretion measured in the supernatant was the same whether INS-1 cells were treated by dopamine or Lodosyn or untreated. CONCLUSION: We validate PET with as a consistent test to differentiate diffuse and focal HI.

BACKGROUND: Congenital hyperinsulinism (CHI) is associated with focal hyperplasia of endocrine tissue in 40-65% of patients. Focal CHI is sporadic and is caused by a germline, paternally inherited, mutation of the SUR1 (ABCC8) or KIR6.2 (KCNJ11) genes (encoding subunits of the pancreatic ATP-dependent potassium channel) together with somatic maternal haploinsufficiency for 11p15.5. Plurifocal or large forms of focal CHI are a cause of apparent failure of surgery, and their underlying mechanism has not been thoroughly investigated. PATIENTS: We here report two patients with bifocal CHI as evidenced by relapsing hypoglycemia after removal of the first focal lesion and the detection of a second, distinct, focal adenomatous hyperplasia during later surgery (patients 1 and 2) and a patient with a giant focal lesion involving the major part of the pancreas (patient 3). RESULTS: In the three patients, a germline, paternally inherited, mutation of SUR1 was found. In patients 1 and 2, haploinsufficiency for the maternal 11p15.5 region resulted from a somatic deletion specific for each of the focal lesions, as shown by the diversity of deletion break points. In patient 3, an identical somatic maternal 11p15 deletion demonstrated by similar break points was shown in two independent lesion samples, suggesting a very early event during pancreas embryogenesis. CONCLUSION: Individual patients with focal hyperinsulinism may have more than one focal pancreatic lesion due to separate somatic maternal deletion of the 11p15 region. These patients and those with solitary focal lesions may follow the two-hit model described by Knudson. The stage of embryogenesis at which the somatic event occurs may account for the observed histological diversity (early event giant lesion, later event small lesion).