Screening for hereditary diseases

From WikiLectures

Genetic screening is part of health care programs today. Originally, it was about identifying newborns with a genetically determined disease that is treatable in case of early diagnosis, e.g. PKU. The main role of genetic screening is to improve the health of society.

Newborn Screening Programs[edit | edit source]

Searchtool right.svg For more information see Newborn Screening.

Principles of an adequate screening-test:

  • the disease state must not only be clearly defined, but also treatable and its incidence in the monitored population must be significant
  • the examination itself must be done quickly and easily on a large number of samples
  • the test should have few false positives and, if possible, zero false negatives
  • completion of diagnosis and initiation of treatment must be well organized and prompt
  • if these conditions are not met, complications will occur

Screening of heterozygotess[edit | edit source]

'Conditions for enabling the screening test:

  • significant occurrence of the disease in a specific population group
  • availability of a test suitable for mass screening
  • possibility of prenatal diagnosis
  • the following diseases meet these criteria:

1. Tay-Sachs disease[edit | edit source]

  • often occurs in Ashkenazi Jews
  • this is one of several different forms of familial amaurotic idiocy (amaurotic = unclear)
  • the enzyme disorder in this disease is a significant deficiency of hexosaminidase A (hex A), in a wide range of tissues; the role of hex A is to cleave the N-acetyl-galactosamine residue from the polysaccharide chain of the ganglioside molecule. In case of its deficiency, ganglioside accumulates, mainly in brain tissue
  • heterozygotess can be detected by screening blood samples for hexosaminidase activity
  • the disease can be detected by biochemical analysis of cultured amniocytes

2. Sickle cell anemia[edit | edit source]

  • manifests itself practically exclusively in blacks
  • the molecular basis is abnormal hemoglobin – HbS
  • this is a severe hemolytic disease with a characteristic tendency of red blood cells to take an obviously abnormal form in an environment with reduced partial pressure of oxygen
  • clinical picture: anemia, icterus and "crisis", vascular obstruction and painful infarcts of various organs (bones, spleen, lungs)

3. Thalassemia[edit | edit source]

  • heterogeneous group of disorders of HbA chain formation
  • caused by damaged genes for hemoglobin, possibly. deletions

Screening α-fetoprotein in maternal serum (MSAFP)[edit | edit source]

  • possibility of detection of split defects, event. fetal Down syndrome warning

Links[edit | edit source]

Related Articles[edit | edit source]

Source[edit | edit source]

  • ŠTEFÁNEK, Jiří.Medicína, nemoci, studium na 1. LF UK [online].[cit. 11. 2. 2010].<https://www.stefajir.cz/>.
    

.