Systematic genetic testing for recessively inherited monogenic diabetes: a cross-sectional study in paediatric diabetes clinics.

AIMS/HYPOTHESIS: Current clinical guidelines for childhood-onset monogenic diabetes outside infancy are mainly focused on identifying and testing for dominantly inherited, predominantly MODY genes. There are no systematic studies of the recessively inherited causes of monogenic diabetes that are likely to be more common in populations with high rates of consanguinity. We aimed to determine the contribution of recessive causes of monogenic diabetes in paediatric diabetes clinics and to identify clinical criteria by which to select individuals for recessive monogenic diabetes testing. METHODS: We conducted a cross-sectional study of 1093 children from seven paediatric diabetes clinics across Turkey (a population with high rates of consanguinity). We undertook genetic testing of 50 known dominant and recessive causes of monogenic diabetes for 236 children at low risk of type 1 diabetes. As a comparison, we used monogenic diabetes cases from UK paediatric diabetes clinics (a population with low rates of consanguinity). RESULTS: Thirty-four children in the Turkish cohort had monogenic diabetes, equating to a minimal prevalence of 3.1%, similar to that in the UK cohort (p = 0.40). Forty-one per cent (14/34) had autosomal recessive causes in contrast to 1.6% (2/122) in the UK monogenic diabetes cohort (p < 0.0001). All conventional criteria for identifying monogenic diabetes (parental diabetes, not requiring insulin treatment, HbA1c ≤ 58 mmol/mol [≤7.5%] and a composite clinical probability of MODY >10%) assisted the identification of the dominant (all p ≤ 0.0003) but not recessive cases (all p ≥ 0.2) in Turkey. The presence of certain non-autoimmune extra-pancreatic features greatly assisted the identification of recessive (p < 0.0001, OR 66.9) but not dominant cases. CONCLUSIONS/INTERPRETATION: Recessively inherited mutations are a common cause of monogenic diabetes in populations with high rates of consanguinity. Present MODY-focused genetic testing strategies do not identify affected individuals. To detect all cases of monogenic paediatric diabetes, it is crucial that recessive genes are included in genetic panels and that children are selected for testing if they have certain non-autoimmune extra-pancreatic features in addition to current criteria.

The molecular basis and genotype-phenotype correlations of congenital adrenal hyperplasia (CAH) in Anatolian population.

Congenital adrenal hyperplasia (CAH) is an autosomal recessive genetic disorder due to presence of mutations in the genes involved in the metabolism of steroid hormones in adrenal gland. There are two main forms of CAH, classic form and non-classic form. While classic form stands for the severe form, the non-classic form stands for the moderate and more frequent form of CAH. The enzyme deficiencies such as 21-hydroxylase, 11-beta-hydroxylase, 3-beta-hydroxysteroid dehydrogenase, 17-alpha-hydroxylase deficiencies are associated with CAH. In this study, we aimed to investigate CYP21A2, CYP11B1, HSD3B2 genes which are associated with 21-hydroxylase, 11-beta-hydroxylase and 3-beta-hydroxysteroid dehydrogenase enzyme deficiencies, respectively, in 365 individuals by using Sanger sequencing method. We emphasized the classification of variants according their disease causing potential, and evaluated variants' frequencies including newly discovered novel variants. As a result, 32 variants of CYP21A2 including 10 novel variants, 9 variants of CYP11B1 including 3 novel variants and 6 variants of HSD3B2 including 4 novel variants were identified. The conclusions of our study showed that in Anatolia, discovery of novel variants is quite common on account of tremendous ratios of consanguineous marriages which increases the frequency of CAH. These results will contribute to the understanding of molecular pathology of the disease.

Neuro-ichthyotic Syndromes: A Case Series.

BACKGROUND: The neuro-ichthyotic diseases are clinically and genetically heterogeneous. The purpose of this study was to evaluate the clinical and neuroradiological findings and to analyze mutation in 15 patients with neuro-ichthyotic diseases. MATERIALS AND METHODS: We retrospectively analyzed the records of 15 patients with the diagnosis of neuro-ichthyotic diseases. RESULTS: Eight female and seven male patients (age range 11 months-52 years) were investigated. There were eight patients with Sjögren-Larsson syndrome (SLS), five patients with multiple sulfatase deficiency (MSD), one patient with Chanarin-Dorfman's syndrome, and one patient with mental retardation, enteropathy, deafness, neuropathy, ichthyosis, and keratodermia (MEDNIK) syndrome. Parental consanguinity was found in all the patients except one. All patients had ichthyosis. Diagnosis was performed with genetic study. CONCLUSIONS: Because biochemical and clinical findings are variable, the diagnosis is difficult in most of the cases. Detailed skin and physical examinations are mandatory in these patients. Genetic tests are necessary for accurate diagnosis.

Multiple sulfatase deficiency: A case series of four children.

Multiple sulfatase deficiency is biochemically characterized by the accumulation of sulfated lipids and acid mucopolysaccharides. The gene sulfatase-modifying factor 1 (SUMF1), recently identified, encodes the enzyme responsible for post-translational modification of a cysteine residue, which is essential for the activity of sulfatases. We describe clinical findings and mutation analysis of four patients. The patients presented with hypotonia, developmental delay, coarse face, ichthyosis, and hepatosplenomegaly. The diagnosis was made through clinical findings, enzymatic assays, and mutation analysis. We were detected to be homozygous for a novel missense mutation c. 739G > C causing a p.G247R amino acid substitution in the SUMF1 protein.

Inactivating KISS1 mutation and hypogonadotropic hypogonadism.

Gonadotropin-releasing hormone (GnRH) is the central regulator of gonadotropins, which stimulate gonadal function. Hypothalamic neurons that produce kisspeptin and neurokinin B stimulate GnRH release. Inactivating mutations in the genes encoding the human kisspeptin receptor (KISS1R, formerly called GPR54), neurokinin B (TAC3), and the neurokinin B receptor (TACR3) result in pubertal failure. However, human kisspeptin loss-of-function mutations have not been described, and contradictory findings have been reported in Kiss1-knockout mice. We describe an inactivating mutation in KISS1 in a large consanguineous family that results in failure of pubertal progression, indicating that functional kisspeptin is important for puberty and reproduction in humans. (Funded by the Scientific and Technological Research Council of Turkey [TÜBITAK] and others.).