Enhancing fetal outcomes in GCK-MODY pregnancies: a precision medicine approach via non-invasive prenatal GCK mutation detection.

Background: Mutations in the GCK gene cause Maturity Onset Diabetes of the Young (GCK-MODY) by impairing glucose-sensing in pancreatic beta cells. During pregnancy, managing this type of diabetes varies based on fetal genotype. Fetuses carrying a GCK mutation can derive benefit from moderate maternal hyperglycemia, stimulating insulin secretion in fetal islets, whereas this may cause macrosomia in wild-type fetuses. Modulating maternal glycemia can thus be viewed as a form of personalized prenatal therapy, highly beneficial but not justifying the risk of invasive testing. We therefore developed a monogenic non-invasive prenatal diagnostic (NIPD-M) test to reliably detect the transmission of a known maternal GCK mutation to the fetus. Methods: A small amount of fetal circulating cell-free DNA is present in maternal plasma but cannot be distinguished from maternal cell-free DNA. Determining transmission of a maternal mutation to the fetus thus implies sequencing adjacent polymorphisms to determine the balance of maternal haplotypes, the transmitted haplotype being over-represented in maternal plasma. Results: Here we present a series of such tests in which fetal genotype was successfully determined and show that it can be used to guide therapeutic decisions during pregnancy and improve the outcome for the offspring. We discuss several potential hurdles inherent to the technique, and strategies to overcome these. Conclusion: Our NIPD-M test allows reliable determination of the presence of a maternal GCK mutation in the fetus, thereby allowing personalized in utero therapy by modulating maternal glycemia, without incurring the risk of miscarriage inherent to invasive testing.

Noninvasive prenatal diagnosis of Mendelian disorders for consanguineous couples by relative genotype dosage.

Noninvasive prenatal diagnosis relies on the presence in maternal blood of circulating cell-free fetal DNA released by apoptotic trophoblast cells. Widely used for aneuploidy screening, it can also be applied to monogenic diseases (NIPD-M) in case of known parental mutations. Due to the confounding effect of maternal DNA, detection of maternal or biparental mutations requires relative haplotype dosage (RHDO), a method relying on the presence of SNPs that are heterozygous in one parent and homozygous in the other. Unavoidably, there is a risk of test failure by lack of such informative SNPs, an event particularly likely for consanguineous couples who often share common haplotypes in regions of identity-by-descent. Here we present a novel approach, relative genotype dosage (RGDO) that bypasses this predicament by directly assessing fetal genotype with SNPs that are heterozygous in both parents (frequent in regions of identity-by-descent). We show that RGDO is as sensitive as RHDO and that it performs well over a large range of fetal fractions and DNA amounts, thereby opening NIPD-M to most consanguineous couples. We also report examples of couples, consanguineous or not, where combining RGDO and RHDO allowed a diagnosis that would not have been possible with only one approach.

Precision medicine in diabetes: A non-invasive prenatal diagnostic test for the determination of fetal glucokinase mutations.

Hyperglycemia caused by mutations in the glucokinase gene, GCK, is the most common form of monogenic diabetes. Prenatal diagnosis is important, as it impacts on treatment. This study reports a monogenic non-invasive prenatal diagnostic (NIPD-M) test on cell-free DNA in maternal plasma using the relative haplotype dosage. In three pregnancies of two families with known maternal GCK mutations, the fetal genotype was determined unambiguously already at 12 weeks of gestation. In summary, proof is provided of the feasibility for NIPD-M in GCK diabetes.

[Pheochromocytoma and paraganglioma: basics for the general practitioner]. / Phéochromocytome et paragangliome: que doit retenir le praticien?

Pheochromocytomas (PHEO) and paragangliomas (PGL) are rare neuroendocrine tumors secreting catecholamines in most cases. The clinic can be very variable. Morbidity and mortality PHEO and PGL are primarily cardiovascular and haves catecholamine-mediated origin. The PHEO and PGL can sign in with a syndromic association with multiple tumors and genetic counseling is necessary in search of a germline mutation. The first step includes a diagnostic assay of metanephrine and normetanephrines. In case of positive biology a CT or MRI imaging will be needed to locate the tumor. Treatment with alpha-blocker before surgery reduces the perioperative risk. A long term follow up is recommended to detect recurrence.

[News in endocrinology in 2013]. / Endocrinologie.

Transsphenoidal surgery is the treatment of choice for acromegaly due to pituitary adenoma but it is not always possible to reduce or control tumor growth, inhibit GH hypersecretion and normalize IGF-I. The first-line drug treatment in 2013 remains the somatostatin analogues. In 2012 and 2013 have been published several publications presenting the prognosis of well-differentiated thyroid cancers of intermediate risk. Indeed, the dose of radioactive iodine administered to patients with "favorable" histology in this risk category should be reduced without change in prognosis. Elastograhy could, in combination with conventional ultrasound features, allow a better selection of thyroid nodules that need a cytology, with, however, still limitations in the detection of follicular carcinomas.