First report of prenatal diagnosis of genetic congenital deafness in a routine prenatal genetic test.

OBJECTIVE: We aimed to screen for connexin26 gene (GJB2) mutations associated with autosomal recessive non-syndromic neurosensory deafness (NSRD) in a general risk population. METHODS: Screening for the most common connexin26 gene mutations was offered to all women undergoing a second-trimester amniocentesis for fetal karyotype analysis in our Center. After rapid DNA extraction from amniotic fluid, PCR amplification was performed and products analysed to detect mutations of GJB2 gene by a sequencing technique. In particular, we searched for the 20 most frequently reported mutations (out of the approximately 90 so far described) and for which there are commercially available tests. RESULTS: From a total of 4819 consecutive amniotic fluids examined, the following five different heterozygous mutations were detected: 35delG in 80 cases, 167delT in 3 cases and 1 occurrence of each of the following mutations: M34T, 35insG and W77R. From these data, a prevalence of 1 : 56 (1.78%) for the heterozygous condition can be estimated in the Mediterranean general risk population. The striking predominance of 35delG mutation is confirmed. In addition, we detected a homozygous 35delG mutation condition in a foetus of no risk parents. In this case, the early diagnosis permitted prompt application of an acoustic prosthesis allowing for cochlear implantation in due time, with significant improvement of the prognosis. CONCLUSIONS: In a general risk population, a carrier status for congenital deafness can be observed in 1 : 56 (1.78%) amniotic fluids; this is mostly due to the presence of a 35delG mutation of the connexin26 gene. Occasional identification of homozygous states, although rare, allows the best therapeutic approach.

Identification of five new mutations and three novel polymorphisms in the muscle chloride channel gene (CLCN1) in 20 Italian patients with dominant and recessive myotonia congenita. Mutations in brief no. 118. Online.

Autosomal dominant myotonia congenita or Thomsen's disease and autosomal recessive myotonia congenita or Becker's are rare nondystrophic disorders due to allelic mutations of the muscle chloride channel gene, CLCN1. We have analysed all 24 exons of the CLCN1 gene, in a panel of 20 unrelated patients (9 with dominant and 11 with recessive mytotonia congenita). We have found five novel mutations including two missense (V5631, F708L), one nonsense (C481X), one splicing (IVS19+2T->A), and one frameshift (2264delC), and also detected the recurrent R894X mutation. These account for 10 of the 22 recessive alleles examined, while no mutations were found in the dominant form. We report three novel polymorphisms (-134T/G, 898C/A and 2154T/C). Our results support high molecular heterogeneity of these myotonias in Italian population and provide new insight for the diagnosis and genetic counselling of these diseases.

Ultrasound and molecular mid-trimester prenatal diagnosis of de novo achondroplasia.

In a low-risk pregnant patient at 21 weeks' gestation, ultrasound revealed shortening of fetal long bones compatible with achondroplasia. Funipuncture was performed and DNA analysis of fetal blood demonstrated the presence of the GR380R fibroblast growth factor receptor 3 (FGFR3), which is specifically associated with achondroplasia. After termination of the pregnancy, necropsy confirmed the prenatal diagnosis. A certain sonographic diagnosis of fetal de novo achondroplasia is rarely possible prior to viability. The specificity of the FGFR3 causative mutation has added a new diagnostic option which can be applied prenatally for diagnostic validation.

Simultaneous detection of delta F508, G542X, N1303K, G551D, and 1717-1G-->A cystic fibrosis alleles by a multiplex DNA enzyme immunoassay.

We describe the use of a polymerase chain reaction in conjunction with a DNA enzyme immunoassay for the simultaneous detection of five common cystic fibrosis mutations. The method is specific, sensitive, rapid, and proved effective in Guthrie card-based screening of cystic fibrosis mutations.