Mutational analysis of the GYS2 gene in patients diagnosed with ketotic hypoglycaemia.

BACKGROUND: Ketotic hypoglycaemia is a common form of hypoglycaemia in childhood. Biochemically, patients present with fasting hypoglycaemia but with normal hormonal and metabolite profiles (low serum alanine levels in some patients). Glycogen Storage Disease Type 0 (GSD0) is an autosomal recessive disease due to mutations in the GYS2 gene. Patients with GSD0 also present with fasting ketotic hypoglycaemia. The frequency of GSD0 in patients presenting with ketotic hypoglycaemia is not known. OBJECTIVE: To understand the frequency of GSD0 in patients presenting with ketotic hypoglycaemia and to report a novel mutation in the GYS2 gene. SUBJECTS: The GYS2 gene was sequenced in 50 patients diagnosed with ketotic hypoglycaemia. METHODS: All exons (including exon and intron boundaries) of the GYS2 gene were sequenced following amplification of the coding region by polymerase chain reaction (PCR). RESULTS: No mutations in GYS2 were found in 49 patients. One patient had a novel homozygous mutation (c.1802T>G; p. Leu601X) in exon 14 of the GYS2 gene. We believe this is the 18th mutation reported so far. This mutation is predicted to lead to premature truncation of the glycogen synthase protein with no function. This patient presented with fasting ketotic hypoglycaemia associated with postprandial hyperglycaemia and elevated lactate level. CONCLUSIONS: GSD0 is relatively rare in patients presenting with ketotic hypoglycaemia and a normal biochemical profile. Sequencing of the GYS2 gene is more likely to be positive in patients with fasting ketotic hypoglycaemia and concomitant postprandial hyperglycaemia with hyperlactataemia.

Role of 18F-DOPA PET/CT imaging in congenital hyperinsulinism.

Congenital hyperinsulinism is a leading cause of severe hypoglycaemia in the newborn period. There are two (diffuse and focal) histological subtypes of congenital hyperinsulinism. The diffuse form affects the entire pancreas and if medically unresponsive will require a near total (95%-98%) pancreatectomy. The focal form affects only a small region of the pancreas (with the rest of the pancreas being normal in endocrine and exocrine function) and only requires a limited pancreatectomy. This limited section of the focal lesion has the potential for curing the patient. Thus the pre-operative differentiation of these two subgroups is extremely important. Recent advances in Fluorine-18-L-dihydroxyphenylalanine positron emission tomography ((18)F-DOPA PET/CT) have radically changed the clinical approach to patient with congenital hyperinsulinism. In most patients this novel imaging technique is able to offer precise pre-operative localisation of the focal lesion, thus guiding the extent of surgical resection.

Refinement of the critical genomic region for congenital hyperinsulinism in the Chromosome 9p deletion syndrome.

Background: Large contiguous gene deletions at the distal end of the short arm of chromosome 9 result in the complex multi-organ condition chromosome 9p deletion syndrome.  A range of clinical features can result from these deletions with the most common being facial dysmorphisms and neurological impairment. Congenital hyperinsulinism is a rarely reported feature of the syndrome with the genetic mechanism for the dysregulated insulin secretion being unknown.  Methods: We studied the clinical and genetic characteristics of 12 individuals with chromosome 9p deletions who had a history of neonatal hypoglycaemia. Using off-target reads generated from targeted next-generation sequencing of the genes known to cause hyperinsulinaemic hypoglycaemia (n=9), or microarray analysis (n=3), we mapped the minimal shared deleted region on chromosome 9 in this cohort. Targeted sequencing was performed in three patients to search for a recessive mutation unmasked by the deletion. Results: In 10/12 patients with hypoglycaemia, hyperinsulinism was confirmed biochemically. A range of extra-pancreatic features were also reported in these patients consistent with the diagnosis of the Chromosome 9p deletion syndrome. The minimal deleted region was mapped to 7.2 Mb, encompassing 38 protein-coding genes. In silico analysis of these genes highlighted SMARCA2 and RFX3 as potential candidates for the hypoglycaemia. Targeted sequencing performed on three of the patients did not identify a second disease-causing variant within the minimal deleted region. Conclusions: This study identifies 9p deletions as an important cause of hyperinsulinaemic hypoglycaemia and increases the number of cases reported with 9p deletions and hypoglycaemia to 15 making this a more common feature of the syndrome than previously appreciated.  Whilst the precise genetic mechanism of the dysregulated insulin secretion could not be determined in these patients, mapping the deletion breakpoints highlighted potential candidate genes for hypoglycaemia within the deleted region.

Satisfaction of care in a tertiary level diabetes clinic: correlations with diabetes knowledge, clinical outcome and health-related quality of life.

AIM: Patient satisfaction is regarded as an integral component of the quality of medical care. Therefore, as part of an ongoing process of outcome assessment, we analysed levels of satisfaction of care among patients and parents in our diabetes clinic and its relationship to short-term metabolic control outcome, diabetes knowledge and health-related quality of life (HRQOL). METHODS: In 2004, parents and their children aged 5-18 years attending the Royal Children's Hospital (RCH) diabetes clinic completed questionnaires reporting their satisfaction with care provided, HRQOL and diabetes knowledge. Concurrent HbA(1c) levels were also recorded. The reporting profile was 83 patients, 24 fathers and 110 mothers. RESULTS: Generally, both patients and parents were satisfied with diabetes care provided at our tertiary centre. Satisfaction of care was not associated with the clinical outcome of metabolic control (measured by HbA(1c) levels), diabetes knowledge or HRQOL measures. CONCLUSION: Most patients and their parents in the RCH diabetes clinic appear generally satisfied with their diabetes care. The degree of satisfaction of care cannot be presumed according to clinical outcome, diabetes knowledge or HRQOL measures.

Persistent hyperinsulinaemic hypoglycaemia of infancy: 15 years' experience at the Royal Children's Hospital (RCH), Melbourne.

OBJECTIVE: To review the clinical outcome and report our experience of patients with persistent hyperinsulinemic hypoglycaemia of infancy (PHHI). METHODS: Retrospective case series of 14 patients diagnosed with PHHI at the Royal Children's Hospital in Melbourne in the period between 1988 and 2004. Diagnoses of insulinoma, Beckwith syndrome and transient hyperinsulinism were excluded. RESULTS: Six patients (43%) presented on day 1, with a median presenting age of 2.75 months; ten (71.4%) presented with seizures. All were initially treated with diazoxide, of whom six (43%) recovered and are off medication, while four patients (28.5%) required surgery (twice in one patient). One developed permanent diabetes mellitus. Developmental delay occurred in nine (64%), and was severe in two (14.5%) patients, possibly associated with delayed treatment. CONCLUSIONS: PHHI is a rare but severe condition. The aim of management of PHHI should be on the one hand to prevent mental retardation and developmental delay due to severe and persistent hypoglycaemia, and on the other hand to avoid the induction of diabetes mellitus following surgery. Satisfactory outcome depends on early effective medical treatment and judicious use of surgery by an experienced operator.

The heterogeneity of hyperinsulinaemic hypoglycaemia in 19 patients with Beckwith-Wiedemann syndrome due to KvDMR1 hypomethylation.

Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome caused by multiple epigenetic and genetic changes affecting imprinted genes on chromosome 11p15.5. Hypomethylation of KvDMR1 on the maternal allele is the most common genetic cause, and hyperinsulinaemic hypoglycaemia (HH) is the most common biochemical abnormality. We evaluated the correlation between severity of HH and degree of hypomethylation in BWS. Out of the 19 patients with BWS due to KvDMR1 hypomethylation, 10 patients had no HH, 5 had mild transient HH that resolved spontaneously, and 4 required diazoxide therapy for up to 6 months. There was no correlation between the degree of KvDMR1 hypomethylation and severity of HH in the 6 patients studied. All patients also showed marked clinical heterogeneity with respect to the features of BWS. In patients with BWS due to hypomethylation of KvDMR1, the clinical presentation of HH is quite heterogeneous with no correlation with the degree of KvDMR1 hypomethylation.

Galactokinase deficiency in a patient with congenital hyperinsulinism.

BACKGROUND: Galactokinase catalyses the first committed step in galactose metabolism, the conversion of galactose to galactose-1-phosphate. Galactokinase deficiency is an extremely rare form of galactosaemia, and the most frequent complication reported is cataracts. Congenital hyperinsulinism (CHI) is a cause of severe hypoglycaemia in the newborn period. Galactosaemia has not previously been reported in a neonate with concomitant CHI. AIMS: To report the first case of a patient with CHI and galactokinase deficiency, and to describe the diagnostic pitfalls with bedside blood glucose testing in a neonate with combined galactokinase deficiency and CHI. PATIENTS/METHODS: A 3-day-old baby girl from consanguineous parents presented with poor feeding, irritability and seizures. Capillary blood glucose testing using bedside test strips and glucometer showed a glucose level of 18 mmol/L, but the actual laboratory blood glucose level was only 1.8 mmol/L. After discontinuation of oral feeding (stopping provision of dietary galactose), the bedside capillary blood glucose correlated with laboratory glucose concentrations. RESULTS: Biochemically the patient had CHI (blood glucose level 2.3 mmol/L with simultaneous serum insulin level of 30 mU/L) and galactokinase deficiency (elevated serum galactose level 0.62 µmol/L). Homozygous loss of function mutations in ABCC8 and GALK1 were found, which explained the patient's CHI and galactokinase deficiency, respectively. CONCLUSION: This is the first reported case of CHI and galactokinase deficiency occurring in the same patient. Severe hypoglycaemia in neonates with CHI may go undetected with bedside blood glucose meters in patients with galactokinase deficiency.

The heterogeneity of focal forms of congenital hyperinsulinism.

BACKGROUND: Congenital hyperinsulinism (CHI) is a cause of persistent hypoglycemia due to unregulated insulin secretion from pancreatic ß-cells. Histologically, there are two major subgroups, focal and diffuse. Focal CHI is typically unresponsive to diazoxide and can be cured with surgical removal of the focal lesion. AIMS: We report on three patients with focal CHI to illustrate the marked clinical, genetic, radiological, and histological heterogeneity. METHODS AND RESULTS: The first two patients had focal CHI due to a paternal (c.3992-9G→A) ABCC8 mutation. One of these patients was fully responsive to a small dose (5 mg/kg · d) of diazoxide, whereas the other patient was medically unresponsive. In both patients, the focal lesions were accurately localized preoperatively by [(18)F]dihydroxyphenylalanine (DOPA) positron emission tomography (PET) and surgically resected. The third patient had a paternally inherited ABCC8 (A1493T) mutation, and the initial [(18)F]DOPA PET scan indicated extensive uptake of DOPA in the body and tail of the pancreas. However, despite surgical resection of the body and tail, this patient continued to have severe CHI. A subsequent [(18)F]DOPA PET scan now showed markedly increased DOPA uptake in the remaining body and head of the pancreas. This focal lesion occupied virtually the whole of the pancreas. conclusions: These three cases illustrate that focal lesions even with the same genotype (c.3992-9G→A) may have a different clinical presentation and that [(18)F]DOPA PET scans in very large focal lesions may be difficult to interpret.

Familial focal congenital hyperinsulinism.

BACKGROUND: Congenital hyperinsulinism (CHI) is a cause of persistent hypoglycemia. Histologically, there are two subgroups, diffuse and focal. Focal CHI is a consequence of two independent events, inheritance of a paternal mutation in ABCC8/KCNJ11 and paternal uniparental isodisomy of chromosome 11p15 within the embryonic pancreas, leading to an imbalance in the expression of imprinted genes. The probability of both events occurring within siblings is rare. AIM: We describe the first familial form of focal CHI in two siblings. PATIENTS AND METHODS: The proband presented with medically unresponsive CHI. He underwent pancreatic venous sampling and Fluorine-18-L-dihydroxyphenylalanine positron emission tomography scan, which localized a 5-mm focal lesion in the isthmus of the pancreas. The sibling presented 8 yr later also with medically unresponsive CHI. An Fluorine-18-L-dihydroxyphenylalanine positron emission-computerised tomography scan showed a 7-mm focal lesion in the posterior section of the head of the pancreas. Both siblings were found to be heterozygous for two paternally inherited ABCC8 mutations, A355T and R1494W. Surgical removal of the focal lesions in both siblings cured the Hyperinsulinaemic hypoglycaemia. CONCLUSION: This is the first report of focal CHI occurring in siblings. Genetic counseling for families of patients with focal CHI should be recommended, despite the rare risk of recurrence of this disease.

The predictive value of preoperative fluorine-18-L-3,4-dihydroxyphenylalanine positron emission tomography-computed tomography scans in children with congenital hyperinsulinism of infancy.

BACKGROUND/PURPOSE: In congenital hyperinsulinism (CHI) of infancy, the use of preoperative fluorine-18-L-3,4-dihydroxyphenylalanine-positron emission tomography-computed tomography ((18)F-DOPA-PET-CT) scan has recently been reported. The aim of this study was to evaluate the accuracy of this technique in discriminating between diffuse and focal CHI and the anatomical localization of focal lesions. METHODS: Between 2006 and 2010, (18)F-DOPA-PET scan was performed in 19 children with CHI (median age, 2 months; range, 1-12 months) who were not responding to medical therapy and underwent laparoscopic or open surgery. The findings of (18)F-DOPA-PET scan were correlated with histology. RESULTS: In 5 children, (18)F-DOPA-PET scan showed diffuse pancreatic uptake, confirmed at histology and supporting the genetic suspicion of diffuse disease. In 14 children, (18)F-DOPA-PET scan indicated focal pancreatic uptake, which corresponded to histology. However, in 5 patients (36%), (18)F-DOPA-PET scan was inaccurate in defining the location of the lesion (n = 3), size of the lesion (n = 1), or both location and size (n = 1), leading to an inaccurate pancreatic resection. CONCLUSIONS: Fluorine-18-L-3,4-dihydroxyphenylalanine-positron emission tomography-computed tomography scan discriminates between diffuse and focal forms of CHI. In focal forms, (18)F-DOPA-PET scan is useful in 2/3 of patients in defining the site and dimension of the focal lesion. Intraoperative histologic confirmation of complete focal lesion resection is needed.