Something went wrong: 5 of the most rare genetic diseases

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© Christopher Conte

Hereditary diseases in medical practice are quite common. Hemophilia, down's syndrome, color blindness, lactose intolerance — all are diseases that arise as a result of mutations and can be passed from generation to generation. However, there are rare genetic diseases, which is capable of diagnosing every specialist. Fatal familial insomnia Death without sleep

Fatal familial insomnia is a rare hereditary disease in which a man dies from inability to sleep. Still it occurred only in 40 families worldwide. Fatal insomnia is usually manifested between 30 and 60 years (most often after 50 years) and lasts from 7 to 36 months. As the disease progresses, the patient suffers from increasingly severe sleep disorders, and no sleeping pills do not help him. In the first stage insomnia accompanied by panic attacks and phobias, second added to them hallucinations and excessive sweating. In the third stage the person with Alzheimer's loses the ability to sleep and begins to look much older than his years. Then develop dementia, and the patient dies, usually from starvation or pneumonia.

Fatal insomnia arises from the fact that the codon (which encodes trinucleotide) 178 of the PRNP gene, located in 20-th chromosome, instead of the asparagine, which is normally present in the body composed of protein and necessary for normal functioning of the nervous system, there is aspartic acid. This changes the shape of the protein molecule, and it becomes prion — aggressive abnormal protein, which no nucleic acids. Under the action of one of the surrounding prion molecules like him, and this leads to irreversible changes. Before that, they occur in the tissues of the thalamus: subcortical stations of all kinds of sensitivity, responsible in particular for the occurrence of the sleepy state and motor function: swallowing, sucking, chewing, laughing. Under the action of prions, the nuclei of the thalamus are covered with pores, turn into a sponge and stop working.

The disease is characterized by autosomal-dominant type of inheritance: that is, it has no speakers. It is transmitted to children from parents with a probability of 50% and only if one of them is sick. Men and women suffer from fatal familial insomnia with the same frequency. Today this disease is considered incurable.

Narcolepsy-cataplexy attack Sleepy

Syndrome narcolepsy-cataplexy, which is characterized by sudden attacks of sleep and relaxation of the muscles of the body, too, is of genetic nature and occurs due to violations of the fast phase of sleep. It is far more common fatal familial insomnia: in 40 out of every 100 thousand people, equally men and women. A person suffering from narcolepsy can suddenly fall asleep for a few minutes in the middle of the day. "Sleep attacks" are reminiscent of REM sleep can happen very often up to 100 times a day, preceding them a headache, or without them. They are often the result of inactivity, but can occur at exactly the wrong time: during sexual intercourse, sports, driving. A man wakes up rested.

Approximately 80% of cases, narcolepsy is accompanied by cataplexy: episodic sudden loss of muscle tone, which is repeated regularly. In mild cases, the patient droops slightly lower jaw and there is a feeling of weakness in the knees, but if the condition is severe, the person may suddenly fall out of the blue. His mind remains clear. Cataplexy develops on the background of expressed emotional reactions: laughter, anger, fear or surprise, which makes this condition especially uncomfortable.

The cause of the disease is not entirely clear, but in some cases the mutation is a mutation of the neurotransmitter orexin (HCRT gene, 17q21), which regulates the process of transmission of excitatory signals in the brain and affects sleep and appetite. Signal system between orexinergic and other neurons fails, inhibited the activity of monoaminergic neurons and reduced the flow of excitatory signals to the cortex.

To remove the narcolepsy-cataplexy is impossible, however, symptomatic treatment is. Patients begin to feel better with regular sleep at certain times and drugs that activate Central adrenergic systems.

Fibrodysplasia Extra bones

Fibrodysplasia ossificans progressive (FOP) is a rare genetic disease in which the body begins to form new bone — ossification — in the wrong places: inside the muscles, ligaments, tendons and other connective tissues. Their education may cause any injury: contusion, laceration, fracture, intramuscular injection or surgery. To remove ecificity impossible: after surgery, the bone can only grow stronger. Physiologically ecificity not differ from ordinary bone and can withstand heavy loads, that just are not where it should be.

FOP is caused by mutation in the gene ACVR1/ALK2, which encodes a receptor for bone morphogenetic protein. It is transmitted to man by inheritance from one of the parents if he is sick, too. To be a carrier of the disease the patient is either sick or not. While the FOP is among the incurable diseases, but now a second series of tests the drug called parovarian that allows you to block the gene responsible for the pathology.

Progeria children, or syndrome Hutchinson-Gilford, is a disease that affects 1 out of 4-7 million children with this diagnosis gets old very quickly and early adolescent patients look and feel as the elderly. They develop many age-related pathologies, disturbances of the internal organs and systems, bones, skin, muscles and tendons become weak and lethargic. While the level of development of 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, the cause of death was myocardial infarction. Described only one case when a patient with this diagnosis have lived up to 45 years.

The cause of progeria children's spontaneous mutation in one of the two copies (alleles) of the gene LMNA, encoding prelamin A, which is the precursor to Mature forms of laminam A and C. These proteins are required for the shell of cell nuclei were intact and functioned normally. Mutant prelamin And — or "progerin" as I propose to call it by some authors, — accumulates in the cells, so they shrink the nuclear envelope, and the nucleus get the wrong shape. These cells can't divide so the organism loses the ability not only to grow but also to replace the dying cells new.

At the moment, this disease is also considered incurable, however, to extend the life of patients and improve its quality helps a variety of symptomatic treatment and physical activity, especially swimming. These tools allow you to improve the condition of the circulatory system and joints. In addition, using a growth hormone.

Syndrome RAGHAD Sudden obesity

RAGHAD syndrome (Rapid-onset Obesity with Hypothalamic dysfunction, Hypoventilation and Autonomic Dysregulation) is an extremely rare disease in which a person begins to rapidly gain weight and suffer from bulimia, respiratory disease stops breathing during sleep, alveolar hypoventilation and cardiorespiratory stops. Patients with this diagnosis is characterized by the absence of response to increase in blood carbon dioxide.

To date, the world was about 100 cases of this disorder. It usually manifests before the age of 10 years (often about 3 years) and, apparently, is hereditary nature. Despite conducted in the West study, the etiology of the syndrome RAGHAD is still not clear. It is believed that it occurs due to dysfunction of the pituitary gland, which causes genetic mutation. However, scientists have yet to determine what the process is broken in this case.




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