ABCC8 and KCNJ11 molecular spectrum of 109 patients with diazoxide-unresponsive congenital hyperinsulinism

BACKGROUND

Congenital hyperinsulinism (CHI) is characterised by an over secretion of insulin by the pancreatic β-cells. This condition is mostly caused by mutations in ABCC8 or KCNJ11 genes encoding the SUR1 and KIR6.2 subunits of the ATP-sensitive potassium (K(ATP)) channel. CHI patients are classified according to their responsiveness to diazoxide and to their histopathological diagnosis (either focal, diffuse or atypical forms). Here, we raise the benefits/limits of the genetic diagnosis in the clinical management of CHI patients.

METHODS

ABCC8/KCNJ11 mutational spectrum was established in 109 diazoxide-unresponsive CHI patients for whom an appropriate clinical management is essential to prevent brain damage. Relationships between genotype and radiopathological diagnosis were analysed.

RESULTS

ABCC8 or KCNJ11 defects were found in 82% of the CHI cases. All patients with a focal form were associated with a single K(ATP) channel molecular event. In contrast, patients with diffuse forms were genetically more heterogeneous: 47% were associated with recessively inherited mutations, 34% carried a single heterozygous mutation and 19% had no mutation. There appeared to be a predominance of paternally inherited mutations in patients diagnosed with a diffuse form and carrying a sole K(ATP) channel mutation.

CONCLUSIONS

The identification of recessively inherited mutations related to severe and diffuse forms of CHI provides an informative genetic diagnosis and allows prenatal diagnosis. In contrast, in patients carrying a single K(ATP) channel mutation, genetic analysis should be confronted with the PET imaging to categorise patients as focal or diffuse forms in order to get the appropriate therapeutic management.

Management of Wilms tumors in Drash and Frasier syndromes

BACKGROUND

Children with WT1 gene-related disorders such as Denys-Drash syndrome (DDS) and Frasier syndrome (FS) are at increased risk of Wilms tumor and end-stage renal disease. We investigated whether Wilms tumors in these patients displayed a specific phenotype or behavior and whether nephron-sparing surgery was beneficial.

PROCEDURE

We retrospectively studied all patients with DDS, FS, or other WT1 mutations treated at our institutions between 1980 and 2007.

RESULTS

We identified 20 patients, of whom 18 had benign or malignant tumors. Wilms tumors occurred in 15 patients, being unilateral in 10 and bilateral in 5 (20 tumors). Median age at Wilms tumor diagnosis was 9 months. No patients had metastases. According to the International Society of Pediatric Oncology Working Classification, there were 19 intermediate-risk tumors and one high-risk tumor; no tumor was anaplastic. In patients with nephropathy who underwent unilateral nephrectomy for Wilms tumor or nephron-sparing surgery for bilateral Wilms tumor, mean time to dialysis was 11 or 9 months, respectively. Other tumors included three gonadoblastomas (in two patients), one retroperitoneal soft-tissue tumor, and one transitional cell papilloma of the bladder. Two patients, both with stage I Wilms tumor, died from end-stage renal disease-related complications. The median follow-up time for the 18 survivors was 136 months (range, 17-224 months).

CONCLUSION

Most Wilms tumors in children with WT1-related disorders were early-stage and intermediate-risk tumors, with a young age at diagnosis. In patients without end-stage renal disease, nephron-sparing surgery should be considered for delaying the onset of renal failure.

Chromosome 11p15 paternal isodisomy in focal forms of neonatal hyperinsulinism

CONTEXT

Focal forms of congenital hyperinsulinism are due to a constitutional heterozygous mutation of paternal origin in the ABCC8 gene, more often than the KCNJ11 gene, located in the 11p15.1 region. This mutation is associated with the loss of the maternally inherited 11p15.1 to 11p15.5 region in the lesion. We investigated the possible occurrence of a compensatory duplication of the paternal 11p15.1-11p15.5 region.

MATERIALS AND METHODS

A combined immunohistochemistry and fluorescent in situ hybridization study on beta-cell interphase nuclei with probes covering two genes located in this region (ABCC8 and CDKN1C genes) was performed in four cases of focal forms of hyperinsulinism.

RESULTS

beta-Cells in the lesions of four cases of focal congenital hyperinsulinism were diploid for chromosomes 11 and 13. The 11p15.1 to 11p15.2 and 11p15.4 to 11p15.5 regions containing ABCC8 and CDKN1C genes, respectively, were present with two copies. Loss of the maternal allele was confirmed in these focal lesions with microsatellite markers flanking the ABCC8 and CDKN1C genes, whereas a heterozygous mutation in the ABCC8 gene was inherited from the father.

CONCLUSIONS

There is a duplication of the paternal allele on chromosome 11 in the focal forms of hyperinsulinism lesion. The paternal isodisomy observed rendered the beta-cells homozygous for ABCC8 mutation and harbored a K-channel defect in the lesion similar to that observed in diffuse forms of congenital hyperinsulinism.

Emergency management and conservative surgery of ovarian torsion in children: a report of 40 cases

INTRODUCTION

The authors describe and discuss the clinical and therapeutic features of 40 ovarian torsions (OT) in children with its urgent treatment that has advanced in recent years.

MATERIALS AND METHODS

A retrospective study of 40 cases of OT in 38 children under 16 years of age, excluding adnexal torsions in neonates.

RESULTS

Abdominal and/or pelvic pain was the presenting symptom ; 8 of these children had pain between 2 to 9 months prior to surgery and 27/40 (67.5%) had associated vomiting. Before the procedure, ultrasound (US) diagnosed 29 ovarian lesions, related to 14 mature teratomas (MTE) and 10 cystadenomas (CA), one association of MTE and CA in the same ovary, 2 functional cysts and 2 malignant neoplasms. 19/40 torsions could benefit from conservative management. Eleven torsions occurred, 10/11 of these ovaries had an increased volume, and 5/11 had US evidence of small subcortical cysts. Three detorsions with incomplete removal of CA were followed by enlargement of the tumor and re-torsion in 2 of them. Five children had bilateral ovarian pathology which led to unilateral ovariectomy, while the other benefited from conservative treatment.

CONCLUSIONS

In any girl presenting with abdominal pain, the diagnosis of an ovarian torsion must be considered. US is performed emergently, but only surgery, most often a laparoscopic procedure, assures diagnosis. The treatment of the torsion is an emergency and must be as conservative as possible in order to preserve the ovarian function. Bilateral torsions are not unusual.

Consequences of the ESPE/LWPES guidelines for diagnosis and treatment of disorders of sex development

Ambiguous genitalia of the newborn is the paradigm of a disorder of sex development that demands a multidisciplinary team approach to management. The problem is immediately apparent at birth. Abnormalities of the external genitalia sufficient to warrant genetic and endocrine studies occur in one in 4500 births. In recent decades there have been improvements in diagnosis and early management, particularly with respect to congenital adrenal hyperplasia, the commonest cause of ambiguous genitalia of the newborn. However, dissatisfaction with overall management remains. A Clinical Guidelines and Handbook for Parents generated by a partnership of health professionals and support groups is available on the internet. The professional societies representing paediatric endocrinology responded by organizing a consensus meeting on the management of intersex. This resulted in the publication of a Consensus Statement encompassing many aspects of management, extending from birth to adulthood.

The Long-Term Followup of 33 Cases of True Hermaphroditism: A 40-Year Experience With Conservative Gonadal Surgery

PURPOSE

Little is known about long-term outcomes of conservative gonadal surgery in true hermaphroditism. We present our experience with evaluation and treatment of a large series of children with this rare form of ambiguous genitalia, focusing on gonadal structure and function before and after conservative gonadal surgery.

MATERIALS AND METHODS

We retrospectively reviewed 33 consecutive patients with histologically confirmed true hermaphroditism treated at the Hopital des Enfants-Malades between 1965 and 2005.

RESULTS

The most common karyotype of true hermaphrodites was 46,XX, constituting 82% of our series. The frequency of finding the SRY gene in 46,XX cases was 35%. Ovotestis was the most frequent finding (65%) and testis the rarest (9%). Ovarian tissue was more often found on the left side, and testicular tissue on the right side (p <0.05). Proper gonadal tissue was preserved in 28 cases. No gonadal tumors were detected during followup. Ovarian tissue remained normal, while testicular tissue gradually developed signs of dysgenesis in all biopsied cases, confirmed by endocrinological studies. However, testosterone production remained satisfactory in the majority of cases during followup.

CONCLUSIONS

Diagnosis of true hermaphroditism is well defined and the condition can be recognized even prenatally. Conservative gonadal surgery is the procedure of choice after a diagnosis of true hermaphroditism. Continued followup is necessary because of the multiple psychological, gynecological and urological problems encountered postpubertally by these patients.

Does Surgical Genitoplasty Affect Gender Identity in the Intersex Infant?

There is no clear-cut answer to the question of whether surgical genitoplasty affects gender identity in the intersex infant. The debate centres around which is more important for the development of gender identity: the biological sex of a child or the sex in which a child is reared. We believe that the surgical achievement of a phenotype concordant with the sex of rearing is a tremendous help to the parents of an intersex infant. We do not consider that the 'neutral' upbringing of a child with ambiguous genitalia is a feasible option, first because of the parents' distress which prevents them from raising their child normally and second because in most cultures around the world gender variants are not treated as equals. A neutral upbringing may induce psychosocial consequences that are more pernicious than carefully considered neonatal sex attribution and concordant surgical genitoplasty.

[Congenital hyperinsulinism in newborn and infant]

Congenital hyperinsulinism (HI) is the most important cause of hypoglycaemia in early infancy. The inappropriate oversecretion of insulin is responsible for profound hypoglycaemias requiring aggressive treatment to prevent severe and irreversible brain damage. Several classifications of HI can be attempted, based on: 1) the onset of hypoglycemia in the neonatal period or later in infancy; 2) the histological lesion: focal or diffuse; 3) the genetic transmission: sporadic, recessive, or less frequently dominant. The most common underlying mechanism of HI is dysfunction of the pancreatic ATP-sensitive potassium channel (K(+)(ATP)). The 2 subunits of the K(+)(ATP) channel are encoded by either the sulfonylurea receptor gene (SUR1 or ABCC8) or the inward-rectifying potassium channel gene (KIR6.2. or KCNJ11), both located in the 11p15.1 region. Focal CHI has been shown to result from a paternally inherited mutation on the SUR1 or KIR6.2 gene and loss of the maternal 11p15 allele restricted to the pancreatic lesion. Diffuse HI, frequently due to mutations of the SUR1 or KIR6.2 genes of autosomal recessive inheritance is genetically heterogeneous. The distinction between the focal and the diffuse HI is very important, because the treatments are different. To distinguish between focal and diffuse HI, transhepatic catheterisation with pancreatic venous sampling was the reference technique, but will likely be replaced by [(18)F] Fluoro-L-Dopa PET scan, which is easier to perform. In absence of response to the medical treatment (diazoxide) a limited pancreatectomy permits to cure focal HI, while a diffuse HI requires a subtotal pancreatectomy with high risk of subsequent diabetes mellitus.

Hermaphroditism pathology

Hermaphroditism is a more general term for the discrepancy between the phenotype and the genotype of sex development than sexual ambiguity, which refers mainly to external genitalia anomalies. Hermaphroditism is studied on an historical and pathogenetical perspective. Short embryological summaries are integrated. The defects of sexual differentiation due to a hormonal deficiency are first studied: androgen insensitivity, steroid 5 alpha-reductase 2 deficiency, defects of testosterone synthesis, persistent mullerian ducts syndrome. Sexual determinism deficiencies come after: Turner syndrome, XX males, pure gonadal dysgenesis, and true hermaphroditism, mixed gonadal dysgenesis, Drash and Frasier syndrome. Tumors of dysgenetic gonads followed. Mixed tumors developed in dysgenetic gonads are gonadoblastoma and dysgerminoma. Sex cord tumors are androgen insensitivity associated tumors, Leydig cells tumors and adrenal cell inclusion tumors. New perspectives open by sex reversion genes are open.

Congenital hyperinsulinism and mosaic abnormalities of the ploidy

BACKGROUND

Congenital hyperinsulinism and Beckwith-Wiedemann syndrome both lead to beta islet hyperplasia and neonatal hypoglycaemia. They may be related to complex genetic/epigenetic abnormalities of the imprinted 11p15 region. The possibility of common pathophysiological determinants has not been thoroughly investigated.

OBJECTIVE

To report abnormalities of the ploidy in two unrelated patients with congenital hyperinsulinism.

METHODS

Two patients with severe congenital hyperinsulinism, one overlapping with Beckwith-Wiedemann syndrome, had pancreatic histology, ex vivo potassium channel electrophysiological studies, and mutation detection of the encoding genes. The parental genetic contribution was explored using genome-wide polymorphism, fluorescent in situ hybridisation (FISH), and blood group typing studies.

RESULTS

Histological findings diverged from those described in focal congenital hyperinsulinism or Beckwith-Wiedemann syndrome. No potassium channel dysfunction and no mutation of its encoding genes (SUR1, KIR6.2) were detected. In patient 1 with congenital hyperinsulinism and Beckwith-Wiedemann syndrome, paternal isodisomy for the whole haploid set was homogeneous in the pancreatic lesion, and mosaic in the leucocytes and skin fibroblasts (hemihypertrophic segment). Blood group typing confirmed the presence of two erythroid populations (bi-parental v paternal only contribution). Patient 2 had two pancreatic lesions, both revealing triploidy with paternal heterodisomy. Karyotype and FISH analyses done on the fibroblasts and leucocytes of both patients were unremarkable (diploidy).

CONCLUSIONS

Diploid (biparental/paternal-only) mosaicism and diploid/triploid mosaicism were present in two distinct patients with congenital hyperinsulinism. These chromosomal abnormalities led to paternal disomy for the whole haploid set in pancreatic lesions (with isodisomy or heterodisomy), thereby extending the range and complexity of the mechanisms underlying congenital hyperinsulinism, associated or not with Beckwith-Wiedemann syndrome.

Hyperinsulinisme persistant du nouveau-né et du nourrisson : traitement chirurgical des lésions pancréatiques focales dans 60 cas

Congenital hyperinsulinism of infancy is a severe disease that leads to important brain damage. Two different forms of the disease have been identified by pathologists: a diffuse and a focal form. A specific genetic anomaly identified in focal forms has never been described in diffuse ones. However, for most of authors, failure of medical treatment results in near-total pancreatectomy in all cases, which ends in diabetus. The aim of this retrospective study was to assess the results of elective partial pancreatectomy performed in 60 cases of focal form of hyperinsulinism over the last 18 years. Fifty-eight patients were cured with euglycemia at both fasting and hyperglycaemic tests without insulin-dependent diabetes mellitus. One patient is still in hypoglycaemia from unrecognized lesion; insulin-dependent diabetes mellitus occurred in one case nine years after surgery (a near-total pancreatectomy has been performed because of unknown focal form, in 1985).

Dominantly inherited hyperinsulinaemic hypoglycaemia

Congenital hyperinsulinism (HI), the most important cause of hypoglycaemia in early infancy, is a heterogeneous disease with two types of histological lesions, focal and diffuse, with major consequences in terms of surgical approaches. In contrast to focal islet-cell hyperplasia, always sporadic to our knowledge, diffuse hyperinsulinism is a heterogeneous disorder involving several genes, various mechanisms of pathogenic mutations and different transmissions: (i) channelopathy involving the genes encoding the sulphonylurea receptor (SUR1) or the inward-rectifying potassium channel (Kir6.2) in recessively inherited HI or more rarely dominantly inherited HI; (ii) metabolic disorders implicating the short-chain L-3-hydroxyacyl-CoA dehydrogenase (SCHAD) enzyme inrecessively inherited HI, the glucokinase gene (GK), the glutamate dehydrogenase gene (GLUD1) when hyperammonemia is associated, dominant exercise-induced HI with still-unknown mechanism, and more recently the human insulin receptor gene in dominantly inherited hyperinsulinism. Thus, dominant HI disorders always correspond to diffuse HI, where most hypoglycaemia occur in infancy, and are sensitive to medical treatment. Channel causes could be due to dominant negative mutation with one abnormality in channels composed of four Kir6.2 subunits and four SUR1 subunits, leading to a complete destruction of the channel structure or function, or due to haploinsufficiency with only one functional allele, leading to 50% of functional protein, which is not sufficient to obtain enough opened channels to maintain the membrane depolarized. Metabolic causes are due to a gain of function of enzyme activity (deregulated enzymes), except for physical exercise-induced hyperinsulinaemic hypoglycaemia, of still-unknown cause. Congenital hyperinsulinism (HI) is the most important cause of hypoglycaemia in early infancy (Aynsley-Green et al 2000; Cornblath et al 1990; Pagliara et al 1973; Thomas et al 1977). The inappropriate oversecretion of insulin is responsible for profound hypoglycaemia that requires aggressive treatment to prevent severe and irreversible brain damage (Volpe 1995). HI is a heterogeneous disease associated with several genes, various mechanisms of pathogenic mutations and different transmissions (Dunne et al 2004).

Follow-up of 68 children with congenital adrenal hyperplasia due to 21-hydroxylase deficiency: relevance of genotype for management

The phenotype of congenital adrenal hyperplasia (CAH) varies greatly. The purpose of this study was to optimize diagnosis and follow-up by comparing phenotype with genotype. Sixty-eight patients with CAH due to 21-hydroxylase deficiency were studied by clinical, hormonal, and molecular genetic methods. Patients were classified according to predicted mutation severity: group 0, null mutation (17.6%); group A, homozygous for IVS2 splice mutation or compound heterozygous for IVS2 and null mutations (33.8%); group B, homozygous or compound heterozygous for I172N mutation (14.7%); group C, homozygous or compound heterozygous for V281L or P30L mutations (26.5%); and group D, mutations with unknown enzyme activity (7.4%). All group 0 and A patients had the salt-wasting form, and group C had nonclassical forms. Group B included five salt-wasting and five simple virilizing forms. Groups 0 and A were younger at diagnosis (P < 0.02), and females were more virilized than those in group B. Group B had higher basal plasma 17-hydroxyprogesterone (564 +/- 162 nmol/liter) and testosterone (11 +/- 3 nmol/liter) levels than group C [59 +/- 13 nmol/liter (P < 0.001) and 1.4 +/- 0.2 nmol/liter (P < 0.005), respectively]. Hydrocortisone doses given to groups 0, A, and B were similar at all ages, but lower in group C (P < 0.01). Final height was below target height in classical (n = 16; -2 +/- 0.2 SD score; P < 0.02) and nonclassical (n = 11; -1.2 +/- 0.4 SD score; P < 0.03) forms. The severity of the genetic defects and the clinical-laboratory features are well correlated. Genotyping, combined with neonatal screening and optimal medical and surgical treatment, can help in the management of CAH.

Surgical management and genotype/phenotype correlations in WT1 gene-related diseases (Drash, Frasier syndromes)

BACKGROUND/PURPOSE

The WT1 gene plays a role in urogenital and gonadal development. Germline mutations of this gene have been observed in patients with Drash or Frasier syndrome (Sd). The purpose of this report is to compare phenotype and genotype of these patients.

METHODS

Retrospective study of 12 patients treated since 1980 for WT1 gene-related disorders was conducted.

RESULTS

End-stage renal disease (ESRD) occurred in 9 patients, mostly because of diffuse mesangial sclerosis (DMS) or focal and segmental glomerular sclerosis (FSGS). Seven patients underwent kidney transplantation, and 2 died. Eleven tumors occurred: 8 Wilms' tumors, one soft tissue tumor, one bladder papilloma, and one gonadoblastoma. Wilms' tumors occurred at a younger age than expected. Eight patients had a 46,XY karyotype. One of these XY patients had female phenotype (Frasier syndrome); she was raised as a girl with bilateral gonadectomy. Seven XY patients had ambiguous phenotype; 4 have been raised as boys and 3 as girls. Four patients had a 46,XX karyotype; they had female genitalia and were raised as girls. WT1 gene analysis was performed in 10 patients and showed heterozygous germline mutations in exon 9 (n = 6), intron 9 (n = 1), exon 3 (n = 1), exon 4 (n = 1), or exon 7 (n = 1).

CONCLUSIONS

ESRD was secondary to DMS when exon 9 was mutated, and secondary to FSGS when intron 9 was mutated. When exon 3, 4, and 7 were mutated, no nephropathy has been observed. Wilms' tumors occurred with any kind of WT1 mutation except intron 9. Abnormal sexual differentiation has been observed in all XY patients with WT1 mutation, and the most profound inversion of phenotype was observed with mutation in intron 9. Correlation between phenotype and genotype provides better understanding of the role of WT1, and can help the surgeon in the management of these patients.

Pancreatic arterial calcium stimulation in the diagnosis and localisation of persistent hyperinsulinemic hypoglycaemia of infancy

BACKGROUND

Persistent hyperinsulinemic hypoglycaemia of infancy (PHHI) is often resistant to medical therapy. Surgery is therefore necessary. It is due to focal adenomatous islet-cell hyperplasia treatable by partial pancreatectomy, or diffuse beta-cell hyperfunction, which requires near-total pancreatectomy. Pancreatic venous sampling (PVS) is the reference technique for the preoperative diagnosis and localization of focal forms of PHHI in the pancreas. However, hypoglycaemia is necessary to analyse the results and PVS is technically challenging. Pancreatic arterial calcium stimulation (PACS) is technically easier and does not require hypoglycaemia.

AIM

To study the accuracy in the diagnosis and localization of PHHI.

MATERIALS AND METHODS

PACS was performed in 12 patients and correlated with histology.

RESULTS

The accuracy of PACS is poor in diffuse lesions since only two of six cases were correctly identified by this test. Five of six focal lesions were correctly recognized and located.

CONCLUSIONS

PACS is less accurate than PVS in PHHI. Currently, it should be performed only when PVS fails.

Neurologic outcomes of 90 neonates and infants with persistent hyperinsulinemic hypoglycemia

OBJECTIVE

To evaluate the neurologic outcomes of neonates and infants suffering from persistent hyperinsulinemic hypoglycemia of infancy (PHHI).

METHODS

The neurologic development of 90 PHHI patients was studied retrospectively. Sixty-three patients were treated surgically and 27 were treated medically. Fifty-four patients were neonates, of whom 8 were treated medically and 46 were operated on (19 for a focal adenomatous hyperplasia and 27 for diffuse hyperinsulinism). Thirty-six patients had infancy-onset hyperinsulinism, of whom 19 were treated medically and 17 underwent pancreatectomy (10 patients for a focal adenomatous hyperplasia and 7 for diffuse hyperinsulinism).

RESULTS

Severe psychomotor retardation was found in 7 patients, 6 with neonatal-onset PHHI. Intermediate psychomotor disability existed in 12 patients; epilepsy existed in 16. Neonatal-onset was the main risk factor for severe retardation or epilepsy. Medically treated patients were less severely affected than those treated by surgery, and there was no difference between the diffuse and focal forms of hyperinsulinism.

CONCLUSION

Neonatal hyperinsulinemic hypoglycemia is still a severe disease with an important risk to rapidly develop severe mental retardation and epilepsy.

Loss of imprinted genes and paternal SUR1 mutations lead to focal form of congenital hyperinsulinism

Persistent hyperinsulinaemic hypoglycaemia of infancy (PHHI) is a heterogeneous disorder characterized by profound hypoglycaemia due to inappropriate hypersecretion of insulin. An important diagnostic goal is to distinguish patients with a focal hyperplasia of islet cells of the pancreas (FoPHHI) from those with a diffuse abnormality of islets (DiPHHI), because the management differs significantly. The intriguing similarity between islet cell hyperplasia and tumourigenesis prompted us to investigate whether the imprinted genes in the 11p15 region are involved. Results showed that diffuse forms are caused by constitutional homozygous or compound heterozygous mutations of the SUR1 gene. In contrast, focal forms are caused by loss of the maternally inherited 11p15 region, resulting in both loss of the maternally expressed tumour suppressor genes accounting for hyperplasia and somatic reduction to hemizygosity or homozygosity of the paternally inherited SUR1, limited to the lesion. Thus, this somatic disorder, which leads both to beta-cell proliferation and to hyperinsulinism, can be considered the somatic equivalent, restricted to a microscopic focal lesion, of constitutional uniparental disomy associated with unmasking of a heterozygous parental mutation.

Congenital microgastria with Pierre Robin sequence and partial trismus

A female with congenital microgastria, Pierre Robin sequence and partial trismus is described. This is a previously undescribed association and the etiology of the association is discussed.

Practical management of hyperinsulinism in infancy

Hyperinsulinism in infancy is one of the most difficult problems to manage in contemporary paediatric endocrinology. Although the diagnosis can usually be achieved without difficulty, it presents the paediatrician with formidable day to day management problems. Despite recent advances in understanding the pathophysiology of hyperinsulinism, the neurological outcome remains poor, and there is often a choice of unsatisfactory treatments, with life long sequelae for the child and his or her family. This paper presents a state of the art overview on management derived from a consensus workshop held by the European network for research into hyperinsulinism (ENRHI). The consensus is presented as an educational aid for paediatricians and children's nurses. It offers a practical guide to management based on the most up to date knowledge. It presents a proposed management cascade and focuses on the clinical recognition of the disease, the immediate steps that should be taken to stabilise the infant during diagnostic investigations, and the principles of definitive treatment.

[Molecular genetics of Hirschsprung disease: a model of multigenic neurocristopathy]

Hirschsprung's disease (HSCR, aganglionic megacolon) is a frequent congenital malformation regarded as a multigenic neurocristopathy. Three susceptibility genes have been recently identified in HSCR, namely the RET proto-oncogene, the endothelin B receptor (EDNRB) gene, and the endothelin 3 (EDN3) gene. RET gene mutations were found in significant proportions of familial (50%) and sporadic (15-20%) HSCR, while homozygosity for EDNRB or EDN3 mutations accounted for the rare HSCR-Waardenburg syndrome (WS) association. More recently, heterozygous EDNRB an EDN3 missense mutations have been reported in isolated HSCR patients. Some of these results were obtained after the identification of mouse genes whose natural or site-directed mutations resulted in megacolon and coat color spotting. There is also conclusive evidence for the involvement of other independent loci in HSCR. In particular, the recent identification of neurotrophic factors acting as RET ligands (GDNF and Neurturin) provide additional candidate genes for HSCR. The dissection of the genetic etiology of HSCR disease may then provide a unique opportunity to distinguish between a polygenic and a genetically heterogeneous disease, thereby helping to understand other complex disorders and congenital malformations hitherto considered as multifactorial in origin. Finally, the study of the molecular bases of HSCR is also a step towards the understanding of developmental genetics of the enteric nervous system giving support to the role of the tyrosine kinase and endothelin-signaling pathways in the development of neural crest-derived enteric neurons in human.

Clinical features of 52 neonates with hyperinsulinism

BACKGROUND

Neonatal hyperinsulinemic hypoglycemia is often resistant to medical therapy and is often treated with near-total pancreatectomy. However, the pancreatic lesions may be focal and treatable by partial pancreatic resection.

METHODS

We studied 52 neonates with hyperinsulinism who were treated surgically. The type and location of the pancreatic lesions were determined by preoperative pancreatic catheterization and intraoperative histologic studies. Partial pancreatectomy was performed in infants with focal lesions, and near-total pancreatectomy was performed in those with diffuse lesions. The postoperative outcome was determined by measurements of plasma glucose and glycosylated hemoglobin and by oral glucose-tolerance tests.

RESULTS

Thirty neonates had diffuse beta-cell hyperfunction, and 22 had focal adenomatous islet-cell hyperplasia. Among the latter, the lesions were in the head of the pancreas in nine, the isthmus in three, the body in eight, and the tail in two. The clinical manifestations were similar in both groups. The infants with focal lesions had no symptoms of hypoglycemia and had normal preprandial and postprandial plasma glucose and glycosylated hemoglobin values and normal results on oral glucose-tolerance tests after partial pancreatectomy (performed in 19 of 22 neonates). By contrast, after near-total pancreatectomy, 13 of the patients with diffuse lesions had persistent hypoglycemia, type 1 diabetes mellitus developed in 8, and hyperglycemia developed in another 7; overall, only 2 patients with diffuse lesions had normal plasma glucose concentrations in the first year after surgery.

CONCLUSIONS

Among neonates with hyperinsulinism, about half may have focal islet-cell hyperplasia that can be treated with partial pancreatectomy. These neonates can be identified through pancreatic catheterization and intraoperative histologic studies.

Loss of imprinted genes and paternal SUR1 mutations lead to hyperinsulinism in focal adenomatous hyperplasia

Two types of histopathological lesions, a focal adenomatous hyperplasia of islet cells of the pancreas in about 30% of operated sporadic cases, and a diffuse form can be observed in congenital hyperinsulinism, or Persistent Hyperinsulinemic Hypoglycemia of Infancy (PHHI). In sporadic focal forms, specific losses of maternal alleles (LOH) of the imprinted chromosomal region 11p15, restricted to the hyperplastic area of the pancreas, were observed. Similar mechanisms are observed in embryonal tumors and in the Beckwith-Wiedemann syndrome which is also associated with neonatal but transient hyperinsulinism. However this region also contains the sulfonylurea receptor (SUR1) gene and the inward rectifying potassium channel subunit (KIR6.2) gene, involved in recessive familial forms of PHHI, but not known to be imprinted. We now report somatic reduction to hemizygosity or homozygosity of a paternal SUR1 constitutional heterozygous mutation, in five patients with a focal form of PHHI. Thus this somatic event (LOH) which leads both to b cell proliferation and to hyperinsulinism can be considered as the somatic equivalent, restricted to a microscopic focal lesion, of constitutional uniparental disomy associated with unmasking of a heterozygous parental mutation leading to a somatic recessive disorder.

Evaluation of gonadal function in 107 intersex patients by means of serum antimüllerian hormone measurement

Fetal male sexual differentiation is driven by two testicular hormones: testosterone (synthesized by interstitial Leydig cells) and antimüllerian hormone (AMH; produced by Sertoli cells present in the seminiferous tubules). Intersex states result either from gonadal dysgenesis, in which both Leydig and Sertoli cell populations are affected, or from impaired secretion or action of either testosterone or AMH. Until now, only Leydig cell function has been assessed in children with ambiguous genitalia, by means of testosterone assay. To determine whether serum AMH would help in the diagnosis of intersex conditions, we assayed serum AMH levels in 107 patients with ambiguous genitalia of various etiologies. In XY patients, AMH was low when the intersex condition was caused by abnormal testicular determination (including pure and partial gonadal dysgenesis) but was normal or elevated in patients with impaired testosterone secretion, whereas serum testosterone was low in both groups. AMH was also elevated during the first year of life and at puberty in intersex states caused by androgen insensitivity. In 46,XX patients with a normal male phenotype or ambiguous genitalia, in whom the diagnosis of female pseudohermaphroditism had been excluded, serum AMH levels higher than 75 pmol/L were indicative of the presence of testicular tissue and correlated with the mass of functional testicular parenchyma. In conclusion, serum AMH determination is a powerful tool to assess Sertoli cell function in children with intersex states, and it helps to distinguish between defects of male sexual differentiation caused by abnormal testicular determination and those resulting from isolated impairment of testosterone secretion or action.

[Persistent hyperinsulinemic hypoglycemia in the newborn and infants]

Persistent hyperinsulinemic hypoglycaemia of infancy (PHHI) is the most frequent cause of hypoglycaemia in infancy. Clinical presentation is heterogeneous, with variable onset of hypoglycaemia and response to diazoxide, and presence of sporadic or familial forms. Underlying histopathological lesions can be focal or diffuse. Focal lesions are characterised by focal hyperplasia of pancreatic islet-like cells, whereas diffuse lesions implicate the whole pancreas. The distinction between the two forms is important because surgical treatment and genetic counselling are radically different. Focal lesions correspond to somatic defects which are totally cured by limited pancreatic resection, whereas diffuse lesions require a subtotal pancreatectomy exposing to high risk of diabetes mellitus. Diffuse lesions are due to functional abnormalities involving several genes and different transmission forms. Recessively inherited PHHI have been attributed to homozygote mutations for the beta-cell sulfonylurea receptor (SUR1) or the inward-rectifying potassium-channel (Kir6.2) genes. Dominantly inherited PHHI can implicate the glucokinase gene, particularly when PHHI is associated with diabetes, the glutamate dehydrogenase gene when hyperammonaemia is associated, or another locus.

Paternal mutation of the sulfonylurea receptor (SUR1) gene and maternal loss of 11p15 imprinted genes lead to persistent hyperinsulinism in focal adenomatous hyperplasia

Congenital hyperinsulinism, or persistent hyperinsulinemic hypoglycemia of infancy (PHHI), is a glucose metabolism disorder characterized by unregulated secretion of insulin and profound hypoglycemia. From a morphological standpoint, there are two types of histopathological lesions, a focal adenomatous hyperplasia of islet cells of the pancreas in approximately 30% of operated sporadic cases, and a diffuse form. In sporadic focal forms, specific losses of maternal alleles (LOH) of the imprinted chromosomal region 11p15, restricted to the hyperplastic area of the pancreas, were observed. Similar mechanisms are observed in embryonal tumors and in the Beckwith-Wiedemann syndrome (BWS), also associated with neonatal but transient hyperinsulinism. However, this region also contains the sulfonylurea receptor (SUR1) gene and the inward rectifying potassium channel subunit (KIR6.2) gene, involved in recessive familial forms of PHHI, but not known to be imprinted. Although the parental bias in loss of maternal alleles did not argue in favor of their direct involvement, the LOH may also unmask a recessive mutation leading to persistent hyperinsulinism. We now report somatic reduction to hemizygosity or homozygosity of a paternal SUR1 constitutional heterozygous mutation in four patients with a focal form of PHHI. Thus, this somatic event which leads both to beta cell proliferation and to hyperinsulinism can be considered as the somatic equivalent, restricted to a microscopic focal lesion, of constitutional uniparental disomy associated with unmasking of a heterozygous parental mutation leading to a somatic recessive disorder.

[Mutations of the endothelin-3 gene in isolated and syndromic forms of Hirschsprung disease]

AIMS AND METHODS

Hirschsprung's disease is a frequent congenital malformation regarded as a multigenic neurocristopathy. Three susceptibility genes have been identified in Hirschsprung's disease, namely the RET proto-oncogene, the Glial cell line-Derived Neurotrophic Factor and the endothelin B receptor. A total of 174 probands with isolated Hirschsprung's disease (59 familial, 117 sporadic cases), and 4 patients with associated Waardenburg's syndrome and Hirschsprung's disease (1 familial, 3 sporadic cases) were screened for mutations in the coding sequence of the endothelin 3 gene. The coding sequence of the endothelin 3 gene was analyzed for point mutations, using a combination of SSCP analysis and direct DNA sequencing.

RESULTS

Two heterozygous mutations (A17T and A224T) were identified in two patients with isolated Hirschsprung's disease. Two homozygous truncations mutations (E55X and GC262->T) were identified in patients with the Waardenburg's syndrome/Hirschsprung's disease association.

CONCLUSION

The present data give further support to the role of the endothelin-signaling pathway in the development of neural crest-derived enteric neurons. They also suggest that either recessive and weakly penetrant dominant alleles could occur at the EDN3 locus, depending on the nature of the mutation.

Neonatal hyperinsulinemic hypoglycemia: heterogeneity of the syndrome and keys for differential diagnosis

The two major forms of infantile persistent hyperinsulinemic hypoglycemia require different treatments, but are difficult to differentiate during surgery. Indeed, one is characterized by focal adenomatous hyperplasia often macroscopically invisible, whereas the other consists of a diffuse, but discreet, beta-cell abnormality. We evaluated, in a large series of persistent hyperinsulinemic hypoglycemia, the reliability of two criteria in differentiating these two forms: the mean beta-cell nuclear radius (MNR) and the beta-cell nuclear crowding, i.e. the number of nuclei per 1000 micron 2 beta-cell (BCNC). The values of the largest MNR and of BCNC in cases bearing a focal lesion (respectively, 3.27 microns +/- 0.25 and 14.62 +/- 1.78) were significantly different from those in the diffuse pathology (4.25 microns +/- 0.43 and 10.00 +/- 1.55). Setting the threshold value of MNR at 3.70 microns and that of BCNC at 12.00 enabled correct classification of 90.9% of the diffuse and 100% of the focal forms. beta-Cell nuclear analysis can thus contribute to a subclassification of the syndrome, not allowed by clinical or biological data. If performed during surgery it could help in determining the extent of pancreatectomy necessary to cure the patient, as the diffuse form, with abnormal nuclei in the whole pancreas, requires subtotal to near-total pancreatectomy, whereas the focal form, devoid of abnormal insular beta-cell nuclei, can be cured by partial pancreatectomy.

Somatic deletion of the imprinted 11p15 region in sporadic persistent hyperinsulinemic hypoglycemia of infancy is specific of focal adenomatous hyperplasia and endorses partial pancreatectomy

Sporadic persistent hyperinsulinemic hypoglycemia of infancy (PHHI) or nesidioblastosis is a heterogeneous disorder characterized by profound hypoglycemia due to inappropriate hypersecretion of insulin. An important diagnostic goal is to distinguish patients with a focal hyperplasia of islet cells of the pancreas (FoPHHI) from those with a diffuse abnormality of islets (DiPHHI) because management strategies differ significantly. 16 infants with sporadic PHHI resistant to diazoxide and who underwent pancreatectomy were investigated. Selective pancreatic venous sampling coupled with peroperative surgical examination and analysis of extemporaneous frozen sections allowed us to identify 10 cases with FoPHHI and 6 cases with DiPHHI. We show here that in cases of FoPHHI, but not those of DiPHHI, there was specific loss of maternal alleles of the imprinted chromosome region 11p15 in cells of the hyperplastic area of the pancreas but not in normal pancreatic cells. This somatic event is consistent with a proliferative monoclonal lesion. It involves disruption of the balance between monoallelic expression of several maternally and paternally expressed genes. Thus, we provide the first molecular explanation of the heterogeneity of sporadic forms of PHHI such that it is possible to perform only partial pancreatectomy, limited to the focal somatic lesion, so as to avoid iatrogenic diabetes in patients with focal adenomatous hyperplasia.

Endothelin-3 gene mutations in isolated and syndromic Hirschsprung disease

Hirschsprung disease (HSCR, aganglionic megacolon) is a frequent congenital malformation regarded as a multigenic neurocristopathy. Four susceptibility genes have recently been identified in HSCR, namely the RET proto-oncogene, the glial cell line-derived neurotrophic factor (GDNF), the endothelin B receptor (EDNRB) and the endothelin-3 genes (EDN3). Homozygosity for EDN3 mutations has been previously shown to cause the Shah-Waardenburg syndrome, a combination of HSCR with features of the Waardenburg syndrome. Here, we report on heterozygous EDN3 missense mutations in isolatec HSCR. The present data give further support to the role of the endothelin signaling pathway in the development of neural crest-derived enteric neurons. They also suggest the possibility that either recessive or weakly penetrant dominant alleles could occur at the EDN3 locus, depending on the nature of the mutation.

[Familial adenomatous polyposis and thyroid cancer]

Familial adenomatous polyposis may exhibit extracolonic tumors which include thyroid carcinoma. It has been recently suggested that thyroid carcinomas associated with familial adenomatous polyposis show distinct histologic features different from sporadic follicular or papillary thyroid carcinomas. We report a case of thyroid carcinoma in a young girl affected by familial adenomatous polyposis, whose thyroid tumor exhibited some of these features. This finding confirms the peculiar histologic phenotype of the thyroid carcinomas associated with familial adenomatous polyposis. Alterations of the APC gene responsible for familial adenomatous polyposis may play a role in the development of these thyroid cancers.

Germline mutations of the RET ligand GDNF are not sufficient to cause Hirschsprung disease

Hirschsprung disease (HSCR, aganglionic megacolon) is a common congenital malformation leading to bowel obstruction, with an incidence of 1/5,000 live births. It is characterized by the absence of intrinsic ganglion cells in the myenteric and submucosal plexuses along variable lengths of the gastrointestinal tract. As enteric neurons are derived from the vagal neural crest, HSCR is regarded as a neurocristopathy. On the basis of a skewed sex-ratio (M/F = 4/1) and a risk to relatives much higher than the incidence in the general population, HSCR has long been regarded as a sex-modified multifactorial disorder. Accordingly, segregation analysis suggested an incompletely penetrant dominant inheritance in HSCR families with aganglionosis extending beyond the sigmoid colon. We and others have mapped a dominant gene for HSCR to chromosome 10q11.2 and have ascribed the disease to mutations in the RET proto-oncogene. However, the lack of genotype-phenotype correlation, the low penetrance and the sex-dependent effect of RET mutations supported the existence of one or more modifier gene(s) in familial HSCR. In addition, thus far, RET mutations only accounted for 50% and 15-20% of familial and sporadic HSCR patients, respectively. RET encodes a tyrosine kinase receptor whose ligand was unknown. Recently, the Glial cell line-derived neurotrophic factor (GDNF) has been identified to be a ligand for RET. Moreover, Gdnf-/- knockout mutant mice display congenital intestinal aganglionosis and renal agenesis, a phenotype very similar to the Ret-/- mouse. These data prompted us to hypothesize that mutations of the gene encoding GDNF could either cause or modulate the HSCR phenotype in some cases.

Serial transabdominal amnioinfusion in the management of gastroschisis with severe oligohydramnios

Two fetuses with gastroschisis diagnosed in utero (at 19 weeks' gestation) had severe oligohydramnios at 30 to 31 weeks. Serial transabdominal amnioinfusions were performed to fill the amniotic cavity with saline, thereby avoiding the potential consequences of fetal exposure to severe oligohydramnios. In both cases, premature rupture of membranes occurred at 36 weeks, and the fetuses were delivered by cesarean section. There were minimal lesions of the extraabdominal bowel. After primary closure of the abdomen, the postoperative course was uneventful. These observations show that serial amnioinfusion is a feasible therapeutic approach for severe third-trimester oligohydramnios associated with gastroschisis.

Testicular dysgenesis does not affect expression of anti-müllerian hormone by Sertoli cells in premeiotic seminiferous tubules

Anti-Müllerian hormone (AMH) immunoreactivity was studied on paraffin sections obtained from archival testicular biopsies of 29 children with intersex disorders and of 22 controls. Strong AMH immunoreactivity was observed in Sertoli cell cytoplasm from 8 fetal weeks until puberty. During pubertal maturation, in both normal and intersex patients, AMH expression was present in premeiotic seminiferous tubules, but was no longer detected in neighboring tubules with meiotic development. AMH immunostaining was abolished in the testis of one patient with persistent Müllerian ducts due to a mutation of the AMH gene, but was conserved in the testes of two patients with mutations of the AMH receptor gene. Testicular dysgenesis usually results in sexual ambiguity, with low testosterone and AMH serum levels and persistence of Müllerian derivatives. AMH immunoreactivity was conserved in premeiotic seminiferous tubules of dysgenetic testes, and also in sex-cord cells of a gonadoblastoma. In patients with asymmetric gonadal differentiation, the streak gonad was AMH-negative. In conclusion, secretion of AMH is a constitutive feature of the immature Sertoli cell and its expression is altered only by mutations of the AMH gene, but not by gonadal dysgenesis. The degree of regression of Müllerian ducts and serum AMH levels reflect the number, not the functional value, of Sertoli cells present in the immature testis.

Heterozygous endothelin receptor B (EDNRB) mutations in isolated Hirschsprung disease

Hirschsprung disease (HSCR, aganglionic megacolon) is a frequent congenital malformation regarded as a multigenic neurocristopathy. Two susceptibility genes have been recently identified in HSCR, namely the RET proto-oncogene and the endothelin B receptor (EDNRB) gene. Hitherto however, homozygosity for EDNRB mutations accounted for the HSCR-Waardenburg syndrome (WS) association. Here, we report heterozygous EDNRB missense mutations (G57S, R319W and P383L) in isolated HSCR. These data might suggest that EDNRB mutations could be dosage sensitive: heterozygosity would predispose to isolated HSCR with incomplete penetrance, while homozygosity would result in more complex neurocristopathies associating HSCR and WS features. In addition, the present data give further support to the role of the endothelin-signalling pathway in the development of neural crest-derived enteric neurons.

[Genetics of Hirschsprung disease]

Hirschsprung's disease (HD) is one of the commonest gastrointestinal malformations, as it affects one child out of 5,000 births. It classically induces severe neonatal intestinal obstruction requiring surgical treatment which currently ensures a favourable prognosis for most of the affected children. Although the great majority of cases are sporadic, the existence of familial forms (10% of cases) has allowed localization and then identification of an autosomal dominant gene on chromosome 10, the RET proto-oncogene, responsible for 50% of familial forms and 15% of sporadic cases. A second gene has been recently localized on chromosome 13, the endothelium beta receptor (EDNRB) gene. Two homozygous mutations of the EDNRB gene have been identified in two consanguineous families, in which HD is associated with Waardenburg's syndrome (WS). Other heterozygous mutations have been identified in patients presenting with isolated HD and an 5% of cases of HD can be considered to present mutations of this gene. Finally, the authors have recently identified a mutation of the endothelium gene 3 (EDN3), one of the EDNRB ligands in a patient presenting with a combination of HD and WS. This mutation, present at the homozygous state in this patient, is predictive of complete absence of EDN3 protein: this is therefore the third known gene responsible for HD.

[Genetics of Hirschsprung disease]

Hirschsprung disease (HD) is one of the commonest gastro-intestinal malformations, as it affects one child out of 5,000 births. It classically induces severe neonatal intestinal obstruction requiring surgical treatment which currently ensures a favourable prognosis for most of the affected children. Although the great majority of cases are sporadic, the existence of familial forms (10% of cases) has allowed the localization and then the identification of an autosomal dominant gene on chromosome 10, the RET proto-oncogene, responsible for 50% of familial forms and 15% of sporadic cases. A second gene has been recently localized on chromosome 13, the endothelin beta receptor (EDNRB) gene. Two homozygous mutations have been identified in two consanguineous families, in which HD is associated with Waardenburg syndrome (WS). Other heterozygous mutations have been identified in patients presenting with isolated HD and 5% of cases can be considered to present mutations of this gene. Finally the authors have recently identified a mutation of the endothelin 3 gene (EDN3), one of EDNRB ligands in a patient presenting a combination of HD and WS. This mutation, present at the homozygous state in this patient, is predictive of complete absence of EDN3 protein: this is therefore the third known gene responsible for HD.

Diversity of RET proto-oncogene mutations in familial and sporadic Hirschsprung disease

Hirschsprung disease (HSCR) is a common congenital malformation (1 in 5,000 live births) due to the absence of autonomic ganglia in the terminal hindgut, and resulting in intestinal obstruction in neonates. Recently, a dominant gene for familial HSCR has been mapped to chromosome sub-band 10q11.2 and the disease has been ascribed to mutations in a tyrosine kinase receptor gene mapping to this region, the RET proto-oncogene. Studying the 20 exons of the RET gene by a combination of denaturating gradient gel electrophoresis and single strand conformation polymorphism in a large series of HSCR patients (45 sporadic cases and 35 familial forms), we found mutations of the RET gene in 50% of familial HSCR, regardless of the length of the aganglionic segment. The mean penetrance of the mutant allele in familial HSCR was significantly higher in males (72%) than in females (51%). Most interestingly, mutations at the RET locus accounted for at least 1/3 of sporadic HSCR in our series. These mutations were scattered along the length of the gene. Finally, among the mutations identified in sporadic cases (16/45), seven proved to be de novo mutations suggesting that new mutations at the RET locus significantly contribute to sporadic HSCR. Taken together, the low penetrance of the mutant gene, the lack of genotype-phenotype correlation, the sex-dependent effect of RET mutations and the variable clinical expression of the disease support the existence of one or more modifier genes in familial HSCR.

[Conjoined omphalopagous twins separated at fifteen days of age]

BACKGROUND

Conjoined (siamese) twins represent a rare situation which may occur in 1 of every 50,000 births. A prenatal diagnosis usually leads to stopping pregnancy. We report a case with successful surgical separation at the age of 15 days.

CASE REPORT

Ultrasonographic examination at 20 weeks of gestation showed omphalopagus siamese joined at the abdomen from the xiphoid process to the umbilicus. Conjoined structures included liver. There was a multicystic right kidney in one twin, without other malformation. Karyotype was normal, 46XX. The mother refused interruption of her pregnancy. Both girls were born by cesarean section. Angiography, magnetic resonance imaging and intravenous urography confirmed the ultrasound examination. There was no cross circulation into the liver and the gastrointestinal tract was not conjoined. The twins were separated at 15 days of age with right heminephrectomy of the multicystic kidney. The girls are now 16 months old and are in very good health.

CONCLUSION

Prognosis of siamese twins depends on the nature of joined structures and presence of malformations. Ultrasonographic examination during pregnancy shows the possibility of surgical separation, which is performed by a double anesthetic and surgical pediatric team. Preoperative investigations must include MRI.

True hermaphroditism: genetic variants and clinical management

The diagnosis and management of 22 patients with true hermaphroditism are described. Sixteen of them were first seen before the age of 4 months. The initial manifestations were ambiguous genitalia in 20 cases (two of them identified prenatally by ultrasound examination), isolated clitoromegaly in one, and penile hypospadias plus unilateral cryptorchidism in one. All patients but one had at least one palpable gonad. Eleven of the twelve patients examined before the age of 6 months had basal plasma testosterone levels > 0.4 ng/ml. In older patients the stimulation test was necessary to demonstrate male testosterone secretion. The most common peripheral karyotype was 46,XX (17 cases); the other karyotypes were 47,XXY (1 case) and mosaicism 46,XX/46,XY (2 cases) or 46,XX/47,XXY (2 cases). One of the patients with the 46,XX karyotype had 46,XX/46,XY on fibroblast culture; four had the SRY gene in their leukocytes and one in the tissue taken at gonadal biopsy. A vagina was found in all patients at laparotomy, and a uterus was found in 17 cases (as a hemiuterus in 9). Genitography failed to demonstrate a uterus in only one case. The testicular tissue was dysgenetic but the ovarian tissue was normal. Sex assignment was male in 8 patients (reoriented by us in 2) and female in 14 patients (reoriented by us in 3). Spontaneous pubertal development occurred in the 4 patients (2 boys, 2 girls) with gonadal tissue who reached pubertal age. We conclude that true hermaphroditism is a heterogeneous condition in terms of its genetic background, with a prevalence of the 46,XX karyotype. There may be mosaicism with a Y-bearing cell line limited to the gonad (its frequency is probably underestimated), a paternal meiotic exchange between X and Y occurring in 46,XX cases with SRY, or a lack of the SRY gene, suggesting that other genes working independently of SRY may also determine testicular differentiation.

Mutations of the RET proto-oncogene in Hirschsprung's disease

Hirschsprung's disease (HSCR) is a common condition (1 in 5,000 live births) resulting in intestinal obstruction in neonates and megacolon in infants and adults. This disease has been ascribed to the absence of autonomic ganglion cells, which are derived from the neural crest, in the terminal hindgut. Segregation analyses have suggested incompletely penetrant dominant inheritance in familial HSCR. Recently, a gene for HSCR has been mapped to chromosome 10q11.2 (refs 6, 7). No recombination was observed between the disease locus and the locus for the RET proto-oncogene, a protein tyrosine kinase gene expressed in the cells derived from the neural crest. Here we report nonsense and missense mutations in the extracellular domain of RET protein (exons 2, 3, 5 and 6) in six unrelated probands and show that the mutant genotypes segregate with the disease in HSCR families. Mutations of RET have been previously reported in multiple endocrine neoplasia type 2A (MEN 2A). Thus, germ-line mutations of the RET gene may contribute either to developmental anomalies in HSCR or to inherited predisposition to cancer in MEN 2A.