Unbalanced expression of 11p15 imprinted genes in focal forms of congenital hyperinsulinism: association with a reduction to homozygosity of a mutation in ABCC8 or KCNJ11.

Congenital hyperinsulinism (CHI), previously named persistent hyperinsulinemic hypoglycemia of infancy, is characterized by profound hypoglycemia because of excessive insulin secretion. CHI presents as two different morphological forms: a diffuse form with functional abnormality of islets throughout the pancreas and a focal form with focal islet cell adenomatous hyperplasia, which can be cured by partial pancreatectomy. Recently, we have shown that focal adenomatous hyperplasia involves the specific loss of the maternal 11p15 region and a constitutional mutation of a paternally inherited allele of the gene encoding the regulating subunit of the K(+)(ATP) channel, the sulfonylurea receptor (ABCC8 or SUR1). In the present study on a large series of 31 patients, describing both morphological features and molecular data, we report that 61% of cases (19 out of 31) carried a paternally inherited mutation not only in the ABCC8 gene as previously described but also in the second gene encoding the K(+)(ATP) channel, the inward rectifying potassium channel (KCNJ11 or KIR6.2), in 15 cases and 4 cases, respectively. Moreover our results are consistent with the presence of a duplicated paternal 11p15 allele probably because of mitotic recombination or reduplication of the paternal chromosome after somatic loss of the maternal chromosome. In agreement with the loss of the maternal chromosome, the level of expression of a maternally expressed tumor suppressor gene, H19, was greatly reduced compared to the level of expression of the paternally expressed growth promoter gene, IGF2. The expression of IGF2 was on average only moderately increased. Thus, focal forms of CHI can be considered to be a recessive somatic disease, associating an imbalance in the expression of imprinted genes in the 11p15.5 region to a somatic reduction to homozygosity of an ABCC8- or KCNJ11-recessive mutation. The former is responsible for the abnormal growth rate, as in embryonic tumors, whereas the latter leads to unregulated secretion of insulin.

Brief clinical report: a 46,XY phenotypic female with Smith-Lemli-Opitz syndrome.

A phenotypic female infant with Smith-Lemli-Opitz (SLO) syndrome was found to have a 46,XY karyotype. Autopsy showed normal tests for age and normal Wolffian duct structures. The serum testosterone level was unusually high, suggesting that the failure of virilization of the external genitalia in the child might be due to a defect in testosterone conversion to dihydrotestosterone or a lack of end-organ receptors for the same. An additional feature not previously described in association with SLO syndrome was present, which was clinical hypoglycemia with nesidioblastosis.

The surgical management of hyperinsulinism in infancy due to nesidioblastosis.

Severe neonatal hypoglycemia due to nesidioblastosis demands prompt diagnosis and treatment to prevent mental retardation. Early central venous catheter placement is essential for a constant glucose infusion. At surgery, near-total (95%) pancreatectomy is done, starting at the tail and preserving the spleen. Bipolar electrocoagulation is very useful for the tiny vessels. The uncinate process is removed leaving a small amount of pancreas adjacent to the preserved common bile duct. Three patients, diagnosed shortly after birth, had surgery at 34 days, 2 years, and 17 days of life. Two patients developed staphylococcal infections, one of whom exhibited the "scalded baby" syndrome and required reoperation for evisceration. Insulin was required for one to seven days in two and for three months in one. Diazoxide was needed for 18 months in the initial patient, who did not have uncinate resection. All patients are healthy and off medication with a postoperative follow-up period of 11, 12, and 65 months.

Neonatal islet cell adenoma: a distinct type of islet cell tumor?

An encapsulated, compact-type islet cell adenoma of the pancreas, found in a newborn infant with hyperinsulinemic hypoglycemia, was investigated by conventional histology and immunofluorescence. Although the histologic structure of the tumor was indistinguishable from that of most islet cell tumors of adults, immunofluorescence revealed that the four islet cell hormones (insulin, glucagon, somatostatin, and pancreatic polypeptide) were all present in the tumor. They were stored in different cells that showed the same spatial distribution usually seen in normal islets. We conclude that neonatal islet cell adenoma can be distinguished from those of adults on the basis of the content and topographic distribution of their constituent endocrine cells.

Elevated serum proinsulin in beta cell nesidioblastosis. Report of a case in a newborn.

A newborn infant with severe hypoglycaemia and nesidioblastosis was subjected to subtotal pancreatectomy without any sign of improvement. In spite of very low plasma levels of glucose (i.e. less than 1 mmol/l) plasma insulin concentrations were high (i.e. greater than 700 pmol/l). Plasma proinsulin was considerably enhanced comprising 43% of the total insulin immunoreactivity. Plasma glucagon concentrations were normal. Postoperatively normal to subnormal plasma glucose levels could only be maintained by treatment with frequent meals, diazoxide and intramuscular injections of a long-acting glucagon preparation. With time, signs of mental retardation became obvious.

[Islet cell adenoma with neonatal onset. Clinical, hormonological and ultrastructural study of a case]. / Adénome langérhansien à révélation néo-natale. Etude clinique, hormonologique et ultrastructurale d'une observation

A case of hyperinsulinism occuring in a newborn, with a birthweight of 4,050 g, is reported. The hypoglycaemia was refractory to the usual therapy (increase of glucose administration per os, and I.V., corticosteroids, glucagon, diazoxide). At surgery, undertaken at 9 days of age, an adenomatous nodule was removed along with the left part of the pancreas. Death occurred at 18 days, after the child had developed a transitory acidoketosic diabetes and an encephalopathy. Measurement of insulin by radio-immunoassay revealed a strong increase in the ratio insulin/glycaemia, characteristic of nesidioblastoma, as well as a high concentration of insulin in the tumor as compared to normal tissue. On the ultrastructural level, the observed features differed from those seen in children and adults and showed an abnormal overload of dense deposits in the cytoplasm of some histiocytes.

Congenital insulinoma (nesidioblastoma): ultrastructural evidence for histogenesis from pancreatic ductal epithelium.

An insulinoma removed from a neonate with proved hyperinsulinemia was examined with the electron microscope. The tumor was composed of pancreatic ductal epithelium and beta cells in direct contact and in lobular units. The pattern of the tumor, the morphologic evidence of beta cell-type activity in ductal cells, and the similarity of the arrangement of tumor cells to that observed in islet regeneration after subtotal pancreatectomy in the rat indicate that this tumor originated from ductal epithelium.