1,721,037 research outputs found
The link between cytogenetics and mendelism
No full textHigh resolution chromosome analysis, molecular cytogenetics, and study of the association between specific chromosome rearrangements and single gene disorders have provided a chromosomal basis to a number of mendelian diseases. Deletions and duplications of small regions, usually less than 3 Mb in size, result in an alteration of normal gene dosage of a number of unrelated genes physically close to each other and are responsible for contiguous gene syndromes. For example, haploinsufficiency is implicated for del 8q24.1 in Langer-Giedion syndrome, del 17p13.3 in Miller-Dieker syndrome, and del 22q11.2 in DiGeorge and Velo-cardiofacial syndromes. Another chromosomal mechanism causing mendelian phenotypes is translocation, which may eventually interrupt a disease gene. It is assumed that translocation breakpoints are running through a relevant gene, hindering the production of the gene product. An example is breakage 16p13.3 associated with Rubinstein Taybi syndrome. Females with X/autosome translocations have an almost exclusive inactivation of the normal X. Interruption of a disease gene in the translocated X causes the expression of a mendelian phenotype in the presence of an allelic recessive mutation onto the nonrearranged X. Finally, if a human gene shows exclusive expression from a single parental homologue, ie, it is imprinted, deletion of the chromosomal segment containing the active allele results in structural monosomy and functional nullisomy. This situation is illustrated by Prader-Willi and Angelman syndromes. Over seventy human genes have been precisely assigned to chromosomal regions using a cytogenetic approach. Chromosome techniques combined with molecular methods have proved to have powerful and sensitive diagnostic capabilities
Recurrent triploidy of maternal origin.
No full textTriploidy is the most frequent chromosome aberration in first trimester spontaneous abortions. In contrast to aneuploidies due to nondisjunction, increased maternal age is not a risk factor and the mechanism of triploidy remains poorly understood. To date, recurrence of triploidy of maternal origin has been described only in a few families suggesting some underlying genetic factors. Here, we report on a woman who underwent three consecutive triploid pregnancies, in two of which maternal origin of triploidy was proved by molecular analysis
Majewski osteodysplastic primordial dwarfism type II (MOPD II) complicated by stroke: Clinical report and review of cerebral vascular anomalies.
No full textWe report on a 2 9/12-year-old boy with disproportionate short stature, microcephaly, subtle craniofacial dysmorphisms, and generalized skeletal dysplasia, who developed a left hemiparesis. Brain neuroimaging disclosed a complex cerebral vascular anomaly (CVA) with stenosis of the right anterior cerebral artery and telangiectatic collateral vessels supplying the cerebral cortex, consistent with moyamoya disease. Based on clinical and skeletal features, a diagnosis of Majewski osteodysplastic primordial dwarfism type II (MOPD II) was established. Review of 16 published patients with CVA affected by either Seckel syndrome or MOPD II suggested that CVA is preferentially associated to the latter subtype affecting about 1/4 of the patients
Primary hypothyroidism and osteopenia associated with Neuhauser syndrome.
No full textWe report on a patient affected by Neuhauser megalocornea-mental retardation (MMR) syndrome, presenting with most of the major manifestations of this disorder, in association with primary hypothyroidism and osteopenia. These symptoms, previously reported in single patients, could be discrete features of MMR syndrome
Ablepharon-macrostomia syndrome in a 46-year-old woman.
No full textAblepharon-macrostomia syndrome (AMS) is a rare condition reported to date in 13 patients worldwide. AMS is characterized by absent or short eyelids, absent eyebrows and eyelashes, macrostomia, and external ear abnormalities. Additional features include alopecia or sparse hair, hypoplastic malar region, redundant skin, rudimentary nipples, abnormal genitalia. While the AMS phenotype is well delineated in infants and children, clinical manifestations are rather poorly characterized in adulthood. Here, we report on an Italian woman who received a diagnosis of AMS at the age of 46 years after several surgical treatments. A clinical comparison between our patient and previously reported AMS cases aids in delineating the adult phenotype of AMS and further broadens the clinical spectrum of this condition
A novel patient with Cooks syndrome supports splitting from "classic" brachydactyly type B.
No full textWe report on a 2-year-old girl affected by an isolated form of brachydactyly type B (BDB)-like malformation of the limbs consistent with Cooks syndrome (CS). A literature review was carried out in an attempt to delineate the CS clinical spectrum and separate it from BDB. The two conditions can be differentiated on clinical, radiological, and genetic grounds. In particular, CS shows a characteristic pattern of ungueal and phalangeal anomalies. In the hands, all rays are involved to a similar extent with bulbous tips. The feet are generally more severely affected than the hands. Involvement of the nails appears to be a primary feature and not secondary to phalangeal hypo/aplasia. Also, radial and ulnar rays are similarly affected. The CS clinical spectrum is expanded to include ungueal tumor-like lesions, observed in the present patient
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