1/21. Craniosynostosis associated with ectopia lentis in monozygotic twin sisters.ectopia lentis has rarely been reported to occur in association with craniosynostosis, and this was found only in sporadic cases. We report on twin sisters who underwent surgery for craniosynostosis and later on, at age 3 years, were found to have bilateral ectopia lentis. Molecular studies yielded a probability of monozygosity of more than 0.98. Inheritance of the syndrome may be autosomal dominant, possibly due to a new mutation, autosomal recessive, or X-linked with male lethality.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
2/21. Discordance for keratoconus in two pairs of monozygotic twins.PURPOSE: We present two pairs of monozygotic twins discordant for keratoconus. methods: Two pairs of twins, each with one twin with keratoconus, and available family members were examined clinically and with computer-assisted videokeratography. polymerase chain reaction-based zygosity assays using between nine and 11 unique, anonymous DNA markers were performed on blood obtained from the twins and surviving parents to assess the probability of genetic monozygosity. RESULTS: dna probes showed a >99% probability that each of the two sets of twins was monozygotic. One twin from each pair had clinically diagnosed keratoconus. The remaining twins were normal by clinical examination and corneal topography. Clinical results for all family members examined were normal except that five of 13 from one family and one of six from the other family demonstrated "suspicious" corneal topography. CONCLUSION: Recent advances in knowledge and understanding of the twinning process suggest that monozygotic twins discordant for keratoconus does not preclude the possibility of a significant genetic component.- - - - - - - - - - ranking = 2keywords = probability (Clic here for more details about this article) |
3/21. Discordance of oral-facial-digital syndrome type 1 in monozygotic twin girls.The oral-facial-digital syndrome type 1 (OFD1) includes limb, facial, intraoral malformations and the gene for the disorder was recently mapped to Xp22.3-p22.2. We report on monozygotic twin girls discordant for OFD1. Monozygosity is supported by placental pathology (monochorionic diamniotic) and molecular studies with probability of dizygosity <1 x 10(-6). The affected twin has oral cavity abnormalities including median cleft lip, cleft palate, lobulated hamartomatous tongue, aberrant hyperplastic oral frenula, alveolar notches, and absent lateral incisors. Facial manifestations include telecanthus, hypoplastic alae nasi, and transient neonatal facial milia. The patient also has short and deviated fingers with partial cutaneous syndactyly. At 10 years, she has not had central nervous system or kidney problems. X-inactivation study revealed similar X-inactivation patterns in the lymphoblasts of both twins. We conclude that skewed X-inactivation is an unlikely cause for the discordance, which is more likely due to a postzygotic mutation in the affected twin.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
4/21. poland's syndrome in one identical twin.female twins were evaluated at the Shriners Hospital in Lexington, kentucky. One twin was normal, and the other twin had the classic findings of poland's syndrome, manifested by absence of the pectoralis major and symbrachydactyly of the right upper extremity. Buccal smears from each child were submitted for DNA testing. The test confirmed monozygosity with 99.9% probability. Some previous reports have stated that poland's syndrome is an autosomal dominant, genetically determined trait, whereas others have maintained that there is no genetic association. The original case described by poland in 1841 was his cadaver, and no family history was reported. This twin study provides strong evidence that the condition is not determined by gene transmission.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
5/21. Discordant pursuit asymmetry and esotropia in monozygous twins.PURPOSE: To report the relationship between infantile esotropia and asymmetry of monocular pursuit tracking. DESIGN: Observational family case series. methods: A twin pair discordant for infantile esotropia was confirmed by DNA analysis to be monozygous at 99.95% probability. Digitally sampled electro-oculographic recordings of monocular horizontal pursuit eye movements were performed for the twins and their orthophoric father. RESULTS: Mean directional asymmetry for right and left eyes was 31% and 5% for the esotropic twin, 10% and 8% for the orthophoric twin, and 5% and 6% for the father. The asymmetry was statistically significant only for the deviating right eye of the esotropic twin (P = 0.0217). CONCLUSION: In this family, monocular pursuit asymmetry is probably not a heritable predisposition to infantile esotropia, but a consequence of early strabismus. Discordance of infantile esotropia and pursuit asymmetry in monozygous twins implicates environmental in addition to genetic causes.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
6/21. Variable expression of marfan syndrome in monozygotic twins.A pair of monzygotic twins with the marfan syndrome with variable expression is presented. One of the twins, in addition to more severe musculoskeletal and ocular manifestations, had coarctation of the aorta as the cardiovascular manifestation of this symdrome. Analysis of red cell antigens, serum proteins and dermatoglyphic examination suggests a high probability of monozygosity. Accordingly, the variation in expression of this autosomal dominant disorder between the twins is most likely due to the modifying influences of environmental factors. Also noteworthy is the fact that the resected coarctation tissue demonstrated the histopathologic changes characteristic of cystic medial necrosis, and thus served as an additional piece of evidence supporting the diagnosis of the marfan syndrome. This was of particular importance in view of the absence of any family history of this syndrome and the absence of ectopia lentis or the more typical cardiovascular manifestations in either twin.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
7/21. Monozygotic twins with discordant sexual phenotypes due to different ratios of mosaicism of 47,X,idic(Y),idic(Y)/46,X, idic(Y)/45,X.We report monozygotic twins of different sexual phenotypes. One of the twins had complete female external genitalia except for a mild clitoromegaly. She had bilateral gonads consisting of the wavy stroma and scant dysgenetic seminiferous tubules. No androgen secretion was induced by gonadotrophin stimulation. The other twin had hypospadiac male genitalia. His gonads were located intrascrotally and he had good androgenic response to a stimulation test. Conventional and fluorescence in situ hybridization chromosome analysis disclosed that both twins had a 47,X,idic(Y),idic(Y)/46,X,idic(Y)/45,X and 47,X, mar x 2.ish idic(Y)(q11.2)(DYZ3 x 2)/46,X, mar.ish idic(Y)(q11.2)(DZY3 )/45,X. These twins were clinically monochorionic and allelotype analysis in these twins and their parents with microsatellite markers showed the affirmative probability of 0.999999994 for monozygosity. The ratio of mosaicism, gonadal histology, and testosterone productivity were reasonably correlated to the genital virilization in these monozygotic twins, showing discordant sexual phenotypes.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
8/21. 45,X Turner's syndrome in monozygotic twin sisters.A 7-year-old girl was admitted to the hospital for anaemia, secondary to intestinal blood los (melaena). She was found to have 45,X Turner's syndrome. Her identical twin sister also had Turner's syndrome with a 45,x chromosome complement. According to various criteria the probability of monozygosity was 0.9905. Although the incidence of twinning is greater than usual in families of patients with Turner's syndrome, affected cases have only been observed in twin sisters on six occasions. It seems therefore that the 45,x chromosome complement itself is not a factor predisposing to twinning, but that in some families, a factor is at play, which cuases either twinning or the 45,X aneuploidy, or both.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
9/21. Simultaneous onset of mitral regurgitation requiring surgery due to primary chordal rupture in middle-aged identical twins.Primary chordal rupture is a leading cause of severe mitral regurgitation requiring surgery. It has previously been documented that there is a high probability of the occurrence of primary chordal rupture in patients with histological evidence of myxysomatous changes in the mitral valve. The precise etiology of primary chordal rupture and/or myxysomatous changes remains obscure and the relative contribution of genetic factors is debated. We report a pair of middle-aged identical twins requiring surgery for mitral regurgitation due to primary chordal rupture, and discuss the etiology of primary chordal rupture and/or myxysomatous changes.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
10/21. Monozygotic twins discordant for goldenhar syndrome.OBJECTIVE: To report on a pair of monozygotic female twins discordant for goldenhar syndrome. DESCRIPTION: The affected twin was a girl, who was delivered by caesarean section at 35 weeks' gestation. Her birth weight was 2,170 g, length 42.5 cm, head circumference 30 cm and her Apgar scores were 3/7. After birth the child developed severe respiratory distress and had to be moved to the neonatal intensive care unit (ICU). The other twin was a girl, born weighing 3,200 g with a length of 49 cm, head circumference of 34 cm and Apgar scores of 8/10. She was transferred to the mother-baby unit soon after birth and was discharged two days later. There was no consanguinity between the twins' parents, who were young and healthy at the time of their conception. The affected child's dysmorphic features included left hemifacial microsomia, severe micrognathia, abnormal ears, bilateral preauricular tags and epibulbar dermoid in the right eye. She developed obstructive apnea due to micrognathia and required tracheostomy. Abdominal and cranial ultrasound findings were normal, as was an ophthalmological assessment. spine x-ray showed hemivertebra at T9 and T10. An echocardiogram showed tetralogy of fallot. GTG-banded karyotyping was performed on peripheral blood cells and revealed 46,XX. Zygosity testing established the pair of twins to be monozygotic with a probability greater than 99:1. comment: goldenhar syndrome was diagnosed in one of the twins described here. There are several reports of twins discordant for this disorder and therefore non-genetic factors may also play an important role, for instance vascular disruption during morphogenesis.- - - - - - - - - - ranking = 1keywords = probability (Clic here for more details about this article) |
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