Genetic Mutations : Genetic trisomies/Down's syndrome

Genetic trisomies

Autosomal

Down's syndrome 

Definition
Down syndrome is a birth defect of chromosomal origin which causes mental retardation caused by the presence of a dose of extra chromosomal region that causes down phenotype (21q22).

 caryotype

Genetic aspects

There are over 50 clinical signs of Down syndrome, but it is rare to find all or even most of them in one person.

Some common features include:

·         Weak muscle tone

·         slanted eyes (upward sloping) with folds of skin on the inside corners (called epicanthic folds)

·         Hypermobility (excessive ability to extend the joints)

·         Wide and short hands with a single line in the palm of one or both hands

·         Broad feet with short fingers

·         Flattened nasal bridge

·         Ears short, low

·         Short neck

·         Small head

·         Small oral cavity

·         Cries short, sharp in childhood

Individuals with Down syndrome are usually smaller than their peers without disabilities, and their physical and intellectual development is slower.

Besides having a distinct physical appearance, children with Down syndrome frequently have specific health problems.

Reduced resistance to infection makes these children more prone to respiratory problems. Vision problems such as squint and have farsightedness or nearsightedness are more likely in individuals with Down syndrome, as are the loss of mild to moderate hearing and speech difficulties. Children with Down syndrome may have a tendency to become obese as they grow older. Besides having negative social implications, this weight gain threatens the health and longevity of these individuals.

 

Associated factors

·         Inbreeding: This has been reported by several authors as not to cause mitotic disjunction. Individual characteristics of parents can also cause a higher incidence of Down syndrome.

·         Maternal age: One of the earliest epidemiological characteristics observed is the increased incidence of Down syndrome in older mothers and this is so primarily from a threshold age is around 35 years.

·         Paternal age: Recent studies using more sophisticated statistical techniques have demonstrated a positive relationship between the disease and age of the father from a threshold age of 45 years.

 

Epidemiology

The frequency of congenital malformations in newborns is 3-4%, the DS is on average 1/800 births (Teratology 2000). Representing 5% of spontaneous abortions and 80% of conceptions with this condition are aborted.

In Mexico, there is not epidemiological studies to determine the incidence of this entity.

Diagnosis

Regardless of the age at which the diagnosis of Down syndrome is made, once established it, you must start the affected patient care.

Preimplantation diagnosis

It is a procedure particularly indicated in those carrier couples of chromosomal rearrangements that determine an increased risk of children with phenotypic alterations than the general population, patients with increased maternal age of 35 years and infertility or a history of abortions or products of conception with recurrence aneuploidy, who wish to avoid facing a pregnancy loss by these conditions. The study is conducted in one or two blastomeres at the 8-cell stage (3rd day after conception) using the technique of FISH (fluorescence in situ hybridization).

 

Prenatal diagnosis

Prenatal diagnosis studies carried out at present for the detection of SD are biochemical screening, ultrasound and chromosomal analysis of fetal cells. These studies are performed on both the first and second trimester of pregnancy.

Neonatal diagnosis

Infants with Down syndrome usually are children born at term, with 2500 g average weight, described many signs of this syndrome, but the most prominent are:. Congenital anomalies, development of malignancies, including leukemia and various problems of health.

Age management and monitoring

There is no treatment to correct or reverse trisomy 21. The management is of the consequences of this condition such as: hypothyroidism, infections, leukemia, hypogonadism, endocrine disorders, etc., but not for chromosomal abnormalities.

For individuals with Down syndrome, as for everyone else, progress from childhood to adulthood is complex, not only for themselves but also for their families and communities. These individuals may have different medical complications depending on their age and need special attention as each of these stages.

The surgical management of defects, control heart disease, respiratory or systemic infections and early learning programs, physical medicine and language tracks, are the most common options. Well, if required various drug therapies, for example in the presence of thyroid dysfunction, seizures or psychiatric disorders occur.

At the moment the use of growth hormone therapy, cell or stimulating brain for this condition is not accepted and is controversial the use of alternative therapies supra pharmacological vitamins, minerals, amino acids and hormones doses, as well as plastic surgery purposes aesthetic.  As part of management support, family counseling and genetic counseling it is included.

 

Epidemiological surveillance

The basic objectives of the search and surveillance of Down syndrome are:

·           knowing its frequency - prevalence

·          Analyze causality

·          Assess the needs of health services and programs direct to the same preventive approach.

·         Work on preventive aspects

All birth defects, including Down syndrome, will gradually join the National Epidemiological Surveillance System of the Ministry of Health.

Bibliography:

AURORA APARICIO MANRIQUE. (S/f). Mutations. 05/10/15, de biology 2 website: http://ies.rosachacel.colmenarviejo.educa.madrid.org/aurora.pdf

Jose s. ramil. (S/f). Mutations. 12/10/15, de ciencias Sitio web: http://www.tirsoferrol.org/ciencias/pdf/a10_mutacion.pdf

Paola Cerruti Mainardi. (2006). Orphanet Journal of Rare Diseases. BioMed Central, 33, 1-9.

Enrique Gómez Galán. (S / F). Turner syndrome. 23.10.15, Spanish Association of Pediatrics Website: http://www.spao.es/documentos/biblioteca/entrada-biblioteca-fichero-60.pdf

 

Health Secretary. (2007). National Center for Gender Equity and Reproductive Health. 30 / October / 2015, of Children's Rehabilitation Center Telethon, the Group of Birth Studies AC, John Langdon down Foundation, AC Website: http://www.salud.gob.mx/unidades/cdi/documentos/Sindrome_Down_lin_2007.pdf