Glucocorticoid-Induced Hyperinsulinism in a Preterm Neonate with Inherited ABCC8 Variant.

Glucose homeostasis is a real challenge for extremely preterm infants (EPIs) who have both limited substrate availability and immature glucose metabolism regulation. In the first days of life, EPIs frequently develop transient glucose intolerance, which has a complex pathophysiology that associates unregulated gluconeogenesis, immature insulin secretion, and peripheral insulin resistance. In this population, glucocorticoid therapy is frequently administrated to prevent severe bronchopulmonary dysplasia. During this treatment, glucose intolerance classically increases and may lead to hyperglycemia. We report a case of neonatal hypoglycemia that was concomitant to a glucocorticoids administration, and that led to a congenital hyperinsulinism diagnosis in an EPI with a heterozygous ABCC8 variant. The variant was inherited from his mother, who had developed monogenic onset diabetes of the youth (MODY) at the age of 23. ABCC8 encodes a beta-cell potassium channel unit and causes congenital hyperinsulinism or MODY depending on the mutation location. Moreover, some mutations have been observed in the same patient to cause both hyperinsulinism in infancy and MODY in adulthood. In our case, the baby showed repeated and severe hypoglycemias, which were undoubtedly time-associated with the betamethasone intravenous administration. This hyperinsulinism was transient, and the infant has not yet developed diabetes at three years of age. We take the opportunity presented by this unusual clinical presentation to provide a review of the literature, suggesting new insights regarding the pathophysiology of the beta-pancreatic cells' insulin secretion: glucocorticoids may potentiate basal insulin secretion in patients with ABCC8 mutation.

Myoclonic absence epilepsy with photosensitivity and a gain of function mutation in glutamate dehydrogenase.

Activating mutations in glutamate dehydrogenase (GDH), de novo or dominantly inherited, are responsible for the hyperinsulinism/hyperammonemia (HI/HA) syndrome. Epilepsy has been frequently reported in association with mutations in GDH, but the epilepsy phenotype has not been clearly determined. Here, we describe a family with a dominantly inherited mutation in GDH. The mother, brother and both sisters had myoclonic absence seizures, but only the mother and one sister had the complete HI/HA pattern. For the two sisters with myoclonic absences, epilepsy started during the second year of life while the brother, it started at 6 years. All 3 children showed the same EEG pattern characterized by photosensitive generalized and irregular spike-wave discharges and runs of multiple spikes. The mother's EEG recordings were normal without photosensitivity. Magnetic resonance imaging (MRI) and spectroscopy (MRS) were normal. A direct effect of the GDH mutation, perhaps in combination with recurrent hypoglycemia and chronic hyperammonemia could provide a pathophysiological explanation for the epilepsy observed in this syndrome and these are discussed.

The spectrum of systemic involvement in adults presenting with renal lesion and mitochondrial tRNA(Leu) gene mutation.

The A3243G mutation of the mitochondrial tRNA(Leu) gene has been recently reported in rare patients with focal and segmental glomerulosclerosis (FSGS). However, the full spectrum of systemic and kidney manifestations in adults presenting with this mutation remains poorly defined. Assessment of renal and nonrenal manifestations was performed in nine patients with A3243G mutation and prominent kidney disease diagnosed in adulthood. At first renal evaluation, median age was 35 years. Renal lesions consisted of FSGS (n = 2), tubulointerstitial nephropathy (n = 3), or bilateral enlarged cystic kidneys (n = 1). All but one patient exhibited extrarenal manifestations: deafness (8 of 9) requiring hearing aid in half the cases, diabetes mellitus (3 of 9), neuromuscular involvement (2 of 9), hypertrophic cardiomyopathy (1 of 9), and macular dystrophy (1 of 9). After a median follow-up of 5 yr, five patients progressed to end-stage renal disease between the ages of 15 and 51 years, four being successfully transplanted. Similarly, extrarenal manifestations progressed since all patients had deafness and diabetes (including three posttransplants), while half had neuromuscular, cardiac, or retinal involvement. In the adult patients with A3243G mutation and renal involvement, preexisting deafness is almost consistently found. While FSGS remains the most typical lesion, tubulointerstitial nephropathy or bilateral, enlarged cystic kidneys may also be encountered. In most cases, diabetes mellitus, macular dystrophy, hypertrophic cardiomyopathy, or neuromuscular features occur later in the course of the disease. The severity of the clinical course is heterogeneous, with end-stage renal failure being reached between the second and sixth decades. Renal transplantation may be offered to these patients, despite a high incidence of steroid-induced diabetes mellitus.

Heterogeneity of persistent hyperinsulinaemic hypoglycaemia. A series of 175 cases.

UNLABELLED: Hyperinsulinism is a heterogeneous disorder characterised by severe hypoglycaemia due to an inappropriate oversecretion of insulin. In a personal series of 175 patients investigated for hyperinsulinaemic hypoglycaemia over the last 20 years, we review clinical presentations, molecular studies and therapeutic management of hyperinsulinism. There were 98 neonatal-onset patients, including 86 permanent hyperinsulinism and 12 transient forms, 68 with infancy-onset and nine with childhood-onset. Hyperammonaemia was found in 12 out of 69 patients tested, 4 neonates and 8 infants. Neonates were clinically more severely affected than infants. Diagnosis of infancy-onset hyperinsulinism was often delayed because of less profound hypoglycaemia and better tolerance to hypoglycaemia. Neonates required higher rates of i.v. glucose than infants to maintain normal plasma glucose levels (16 mg/kg per min versus 12 mg/kg per min). Only 16% of neonates were diazoxide-sensitive compared to 66% of the infants. Neonates with hyperammonaemia or transient hyperinsulinism were diazoxide-sensitive. Most neonates were pancreatectomised whereas 65% of the infants were treated medically. Among surgically-treated patients, 47% had a focal adenomatous hyperplasia (31 neonates and 13 infants) and 53% a diffuse form of hyperinsulinism (39 neonates and 11 infants). Diazoxide-responsiveness in the focal and diffuse forms did not differ in both neonates and infants; it depended only upon the age of onset of hypoglycaemia. One or two mutations, SUR1 or KIR6.2, were found in 41 of 73 neonates who were investigated and in 13/38 infants using polymerase chain reaction-single strand conformational polymorphism analysis of both genes. Almost all patients with SUR1 (38/41) or KIR6.2 (5/7) mutations were resistant to diazoxide. Ten patients with hyperinsulinism-hyperammonaemia syndrome had a mutation in the glutamate dehydrogenase gene (three neonates and seven infants) after reverse transcriptase-polymerase chain reaction and sequence analysis of cDNA. No mutation was found by polymerase chain reaction-single strand conformational polymorphism in the glucokinase gene. Eight of nine patients with childhood onset hyperinsulinism were treated surgically and histological examination confirmed an adenoma in each case. CONCLUSION: the clinical severity of hyperinsulinism varies mainly with age at onset of hypoglycaemia. The heterogeneity of hyperinsulinism has major consequences in terms of therapeutic outcome and genetic counselling.