Walter Pinto Júnior

Diagnóstico pré-natal

O presente artigo apresenta uma descricao de todos os metodos de diagnostico pre-natal de anormalidades geneticas e cromossomicas, bem como dos relativos a doencas infecciosas na gravidez. O autor discute as diferencas entre eles, e as novas ferramentas da biologia molecular que sao aplicadas nesses diagnosticos. Ao final e feita uma descricao da tecnica de diagnostico pre-implantacao e de seu uso in vitro em laboratorios de fertilidade situados a mais de dois mil quilometros um do outro.

Frequency of 677C -> T and 1298A -> C polymorphisms in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene in Turner syndrome individuals

Turner syndrome (TS) is an interesting model for investigating the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and non-disjunction because of the high frequency of chromosomal mosaicism among patients with this syndrome. We determined the frequencies of MTHFR 677C ® T and 1298A ® C polymorphic mutations in 49 patients with TS and 200 control individuals. The frequency of the 677C ® T allele was 0.39 for patients and 0.29 for controls while that of the 1298A ® C allele was 0.28 for patients and 0.25 for controls. Genotype frequencies were shown to be different in patients and controls (c2 = 12.143; p = 0.033), and this was attributable to the higher frequency of the C677C ® T /677C ® T genotype among TS patients. In homozygotes, this mutation might have an effect on somatic chromosome disjunction by decreasing MTHFR activity.

Nuchal translucency: an ultrasound marker for fetal chromosomal abnormalities

CONTEXT The literature shows an association between several ultrasound markers and chromosome abnormality. Among these, measurement of nuchal translucency has been indicated as a screening method for aneuploidy. The trisomy of chromosome 21 has been most evaluated. OBJECTIVE To define the best fixed cutoff point for nuchal translucency, with the assistance of the ROC curve, and its accuracy in screening all fetal aneuploidy and trisomy 21 in a South American population. TYPE OF STUDY Validation of a diagnostic test. SETTING This study was carried out at the State University of Campinas, Campinas, Brazil. PARTICIPANTS 230 patients examined by ultrasound at two tertiary-level private centers, at 10 to 14 weeks of gestation. DIAGNOSTIC TEST The participants consisted of all those patients who had undergone ultrasound imaging at 10 to 14 weeks of gestation to measure nuchal translucency and who had had the fetal or neonatal karyotype identified. MAIN MEASUREMENTS Maternal age, gestational age, nuchal translucency measurement, fetal or neonatal karyotype. RESULTS Prevalence of chromosomal defects - 10 %; mean age - 35.8 years; mean gestational age - 12 weeks and 2 days; nuchal translucency (NT) thickness - 2.18 mm. The best balance between sensitivity and specificity were values that were equal to or higher than 2.5 mm for overall chromosomal abnormalities as well as for the isolated trisomy 21. The sensitivity for overall chromosomal abnormalities and trisomy 21 were 69.5 % and 75 %, respectively, and the positive likelihood ratios were 5.5 and 5.0, respectively. CONCLUSION The measurement of nuchal translucency was found to be fairly accurate as an ultrasound marker for fetal abnormalities and measurements equal to or higher than 2.5 mm were the best fixed cutoff points.

Preimplantation genetic diagnosis for cystic fibrosis: a case report

Cystic fibrosis is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator gene. This disorder produces a variable phenotype including lung disease, pancreatic insufficiency, and meconium ileus plus bilateral agenesis of the vas deferens causing obstructive azoospermia and male infertility. Preimplantation genetic diagnosis is an alternative that allows identification of embryos affected by this or other genetic diseases. We report a case of couple with cystic fibrosis; the woman had the I148 T mutation and the man had the Delta F508 gene mutation. The couple underwent in vitro fertilization, associated with preimplantation genetic diagnosis, and with subsequent selection of healthy embryos for uterine transfer. The result was an uneventful pregnancy and delivery of a healthy male baby.

Molecular analysis of the most prevalent mutations of the FANCA and FANCC genes in Brazilian patients with Fanconi anaemia

Fanconi anaemia (FA) is a recessive autosomal disease determined by mutations in genes of at least eleven complementation groups, with distinct distributions in different populations. As far as we know, there are no reports regarding the molecular characterisation of the disease in unselected FA patients in Brazil. OBECTIVE: This study aimed to investigate the most prevalent mutations of FANCA and FANCC genes in Brazilian patients with FA. METHODS: Genomic DNA obtained from 22 racially and ethnically diverse unrelated FA patients (mean age ± SD: 14.0 ± 7.8 years; 10 male, 12 female; 14 white, 8 black) was analysed by polymerase chain reaction and restriction site assays for identification of FANCA (D3788-3790) and FANCC (D322G, IVS4+4A ® T, W22X, L496R, R548X, Q13X, R185X, and L554P) gene mutations. RESULTS: Mutations in FANCA and FANCC genes were identified in 6 (27.3%) and 14 (63.6%) out of 22 patients, respectively. The disease could not be attributed to the tested mutations in the two remaining patients enrolled in the study (9.1%). The registry of the two most prevalent gene abnormalities (D3788-3790 and IVS4 + 4 ® T) revealed that they were present in 18.2% and 15.9% of the FA alleles, respectively. Additional FANCC gene mutations were found in the study, with the following prevalence: D322G (11.4%), W22X (9.1%), Q13X (2.3%), L554P (2.3%), and R548X (2.3%) of total FA alleles. CONCLUSION: These results suggest that mutations of FANCA and FANCC genes are the most prevalent mutations among FA patients in Brazil.

A case of possible genetic predisposition to myelodysplastic syndrome

Herein, we showed with an educational purpose, theimage obtained from the karyotype of one MDS patientwith t(11;21)(q13;q22) seen in our service, whose father,who did not suffer from any haematological disease,presented the same chromosomal abnormality.The patient, a 20-year-old woman, was referred tohospital in May 1999 due to anaemia. No