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Thursday, 11 December 2014

5 Most rare Genetic Diseases

Hereditary diseases in medical practice are quite common. Hemophilia, Down syndrome, blindness, lactose intolerance - all diseases that result from mutations and can be transmitted from generation to generation. However, there are rare genetic disease that is capable of diagnosing every specialist.T & P made a list of them and describe the reasons for the appearance.

Fatal familial insomnia: death without sleep
Fatal familial insomnia - a rare hereditary disease in which a person dies from an inability to sleep. Until now, it was noted only 40 families worldwide. Fatal Insomnia usually manifests between 30 and 60 years (usually - after 50 years) and lasts between 7 to 36 months. As soon as the disease progresses, the patient is suffering from more severe sleep disturbances, and no sleeping pills do not help him. In the first stage insomnia accompanied by panic attacks and phobias, the second added to them hallucinations and increased sweating. At the third stage of the disease a person loses the ability to sleep and begins to look much older than his years. Then developing dementia and patient dies - typically from malnutrition or pneumonia.
Fatal Insomnia arises from the fact that the codon (encoding trinucleotide) 178 gene PRNP, located in chromosome 20 instead of asparagine, which is normally present in the body part and the proteins necessary for normal functioning of the nervous system, appears aspartic acid. This changes the shape of the protein molecule, and it becomes prion - aggressive abnormal protein in the composition which have nucleic acids. Under the influence of a prion molecules surrounding likened him, and this leads to irreversible changes. Before that, they occur in the tissues of the thalamus: subcortical "stations" of all kinds of sensitivity, including responsible for the occurrence of somnolence and motor functions: swallowing, sucking, chewing, laughing. Under the action of prions thalamic nuclei covered pores turn into a sponge and stop working.
The disease is characterized by an autosomal dominant mode of inheritance: that is, it does not have media. Children it is transmitted from parents with a probability of 50%, and only if, if one of them is sick. Men and women suffer Fatal familial insomnia with the same frequency. To date, the disease is considered incurable.
Narcolepsy-cataplexy: "sleepy attack"
Narcolepsy-cataplexy syndrome, which is characterized by sudden attacks of sleep and relaxation of muscles of the body, also has a genetic nature and arises because of the fast phase of sleep disorders. It occurs more often fatal familial insomnia: 40 out of every 100 thousand. People, equally in men and women. A person suffering from narcolepsy, is capable suddenly fall asleep for a few minutes in the middle of the day. "Carotid attack" resemble REM sleep and may happen very often up to 100 times per day, headache preceding them, or without them. They are often triggered by inactivity, but can occur at exactly the wrong time during intercourse, sports, driving.Man wakes up refreshed.
Approximately 80% of cases of narcolepsy cataplexy accompanied by: a sudden episodic loss of muscle tone that is repeated regularly. In mild cases, the patient's lower jaw slightly droops and there is a feeling of weakness in the knees, but if a serious condition, a person can suddenly fall out of the blue. His mind, however, remains unclear. Cataplexy develops in the expression of emotional reactions: laughter, anger, fear or surprise that makes this state is particularly inconvenient.
The cause of the disease while not completely clear, but in some cases, there is a mutation mutation neurotransmitter orexin (gene HCRT, 17q21), which regulates the transfer of excitation signals in the brain and affects sleep and appetite. Signaling system between oreksinergicheskimi and other neurons fails, inhibits the activity of monoaminergic neurons and reduced influx of excitatory signals to the cortex.
Narcolepsy-cataplexy eliminate the impossible, but symptomatic treatment is. Patients begin to feel better through regular sleep at certain times and drugs activates the central adrenergic systems.
FOP: extra bone
Fibrodisplations ossificans progressiva (FOP) - a rare genetic disorder in which the body begins to form new bone - ossification - in the wrong places: within the muscles, ligaments, tendons, and other connective tissues. These can cause the formation of any injury: bruises, cuts, broken, intramuscular injection or surgery. Because it is impossible to remove ossification: after bone surgery can only grow stronger. Physiologically ossification do not differ from ordinary bone and can withstand heavy loads, here are just not where it is necessary.
FOS occurs due to a mutation in the gene ACVR1 / ALK2, encoding a bone morphogenetic protein receptor. It is transmitted to humans inherited from one parent, if he is sick, too. Be a carrier of the disease can not be: the patient either sick or not. While FOP is one of incurable diseases, but now a second series of tests of the drug called palovaroten, which allows you to lock the gene responsible for the pathology.
Progeria: Children age
Children progeria, or Hutchinson-Gilford syndrome - a disease that affects 1 million people from 4-7. The body of children with this diagnosis is aging very quickly and early: already in adolescence patients look and feel like an old man. They have developed a lot of senile pathologies lead to abnormalities in internal organs and systems, bones, skin, muscles and tendons become weak and lethargic. In this case, the level of development, children with progeria are not inferior to their peers, and sometimes ahead of them. The average life expectancy of people suffering from the syndrome of Hutchinson-Gilford - 13 years. As a rule, becomes a cause of death of myocardial infarction. Described only one case where a patient with this diagnosis live up to 45 years.
The cause of the children's Progeria - a spontaneous mutation in one of the two copies (alleles) of the gene LMNA, encoding prelamin A, which is a precursor to the mature forms of lamins A and C. These proteins are required to shell cell nuclei were intact and functioning normally. A mutant prelamin - or "progerin", as suggested by some authors call it - is accumulated in the cells, so that their nuclear membranes shrink and become irregular shape of the nucleus. Such cells can no longer divide normally, so that the body loses its ability to not only grow, but also to replace dying cells with new ones.
At the moment, the disease is also considered incurable, but extend the life of patients and helps improve the quality of a variety of symptomatic treatment and physical activity, especially swimming. These tools can improve the circulatory system and joints. In addition, growth hormone is used.
ROHHAD: sudden obesity
ROHHAD syndrome (Rapid-onset Obesity with Hypothalamic dysfunction, Hypoventilation and Autonomic Dysregulation) - an extremely rare disease in which a person begins to rapidly gain weight and suffer from bulimia, respiratory diseases, pauses in breathing during sleep, alveolar hypoventilation, and cardiorespiratory stops. Also in patients with a diagnosis characteristic lack of response to increasing levels of carbon dioxide.
Today in the world registered about 100 cases of this disorder. Usually it appears in the age of 10 (usually about 3 years), and apparently has a hereditary nature. Despite the research carried out in the West, the etiology of the syndrome ROHHAD still not clear. It is believed that it arises from the dysfunction of the pituitary, which causes a genetic mutation. However, scientists have yet to determine which process is violated in this case.