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Huntington’s disease, cystic fibrosis, phenylketonuria – deadly diseases caused by mutations of only one gene
Dominant
Huntington’s disease
A characteristic feature of the disease is the appearance of its symptoms only in adulthood, when the patients already have their children. If the disease is passed on by the father, the first symptoms appear at an earlier age than in the case of inheritance from the mother. Most often, chorea begins after the age of 30. and the time from disease onset to death is approximately 15 years. Symptoms include chorea, sudden uncontrolled movement disorders, as well as mood disorders and progressive deterioration in mental activity. It is caused by the death of cells in a specific part of the brain called the caudate.
Marfan syndrome (arachnodactyly, finger spider veins)
It is a disease involving, inter alia, skeletal system and affects all parts of the body that are made of connective tissue. Patients have a characteristic body structure, very slim, with elongated limbs and long fingers. The body proportions are incorrect, and the spine is often curved. Breathing is impaired due to the weakness of the chest muscles as well as the curvature of the lateral spine. For this reason, children with Marfan syndrome often develop bronchitis and pneumonia, and many adults suffer from bronchial asthma. The joints are excessively mobile, there are hernias. Patients with Marfan syndrome have a long narrow face, a small lower jaw, a high palate and tightly packed teeth. Mitral valve prolapse or aortic dilatation are observed in the cardiovascular system. This widening can lead to the delamination of this vessel. Lens dislocation, iris abnormalities or congenital cataracts are also characteristic. The intellectual level of patients is usually not abnormal.
Other dominant inheritance disorders include
– familial hypercholesterolaemia
– congenital deafness
– the dominant form of blindness
— achondroplazja
– colon polyposis, etc.
Recessive
Cysticidosis (cystic fibrosis of the pancreas)
It is a disease that occurs, according to various authors, with the frequency of 1 in 2500-5000 people. More than 800 mutations have been described that cause clinical symptoms of cysticidosis, but the most common mutation is the F508 mutation. At present, cystic fibrosis is incurable and is the most often life-threatening disease of all genetically determined.
The basis of cystic fibrosis is an abnormal structure of a protein found in cell membranes, which causes abnormal ion transport, and thus the formation of too sticky mucus. This mucus is located in the respiratory, digestive and reproductive systems, hence the symptoms of cystic fibrosis concern these organs.
– respiratory system
shortness of breath, shortness of breath, paroxysmal cough are often treated as symptoms of infection, and are caused by obstruction of the bronchi and bronchioles by gestures of mucus. This mucus also contributes to the distension of the bronchioles and disrupts their filling with air, as well as facilitates the adherence of bacteria to the epithelium of the respiratory tract. Hence, in sick people frequent respiratory infections. Children constantly expectorate purulent or mucous secretions (expectoration is most intense in the morning), and their exercise tolerance is reduced. The chest has an increased anterior-posterior dimension, it is barrel-shaped. There are also nasal polyps. The persistent narrowing of the bronchioles, bacterial infections, chronic inflammation and exacerbations cause damage to the respiratory system, bronchiectasis, development of the so-called pulmonary heart. Over time, respiratory failure and death develop.
– digestive system
even in newborns, it is possible to suspect cystic fibrosis when they develop the so-called meconium irregularity. This is a condition in which the end of the ileum becomes clogged with a very sticky and thick meconium. Usually, such a child requires surgery. Already from the neonatal period, in patients with cystic fibrosis, disturbances in nutrient absorption are revealed, which are caused by obstruction of the mucus of the pancreatic ducts and, consequently, by exocrine pancreatic insufficiency. The stools donated by patients are very large, gray, foul-smelling and look “oiled”. Despite the perfect, even determined wolf’s appetite, physical development, growth and weight gain are delayed. Characteristic are slim limbs and “no buttocks”. Due to obstruction of the biliary tract, newborns develop prolonged jaundice, and older patients develop biliary cirrhosis.
– other systems
the epididymis and vas deferens ducts clogged with mucus overgrow already in the prenatal period, which causes infertility in 98% of sick men. Also in the cervix, dense mucus makes fertilization difficult.
From the sweat glands, along with sweat, more sodium, potassium and chlorine ions are seen – “salty kisses”. This is not a direct cause of any disease symptoms, only faster dehydration is possible at high ambient temperatures. At the same time, the determination of a higher concentration of chlorine ions in sweat is, apart from clinical symptoms, the basic method of confirming the diagnosis of cystic fibrosis.
Treatment of cystic fibrosis is very complex and difficult. It also requires enormous involvement of parents of sick children and various groups of specialists. The basis of treatment is:
– constant rehabilitation of the chest, in the form of patting in special positions, provoked cough, using special devices. All these activities support the removal of residual mucus from the respiratory tract
– aerosol spray: feeding, among others drugs that relax the mucus secretions (mucolytics), bronchodilators or inhaled steroids
– properly selected and intensive antibiotic therapy, especially in periods of exacerbation of the disease symptoms.
– a suitable, high-calorie diet with a high protein and fat content
– administration of pancreatic enzymes necessary for proper digestion and absorption of food substances; the administered preparations must be resistant to the action of gastric acid
– administration of fat-soluble vitamins
Fenyloketonuria (hiperfenyloalaninemia)
is a disease caused by a lack of an enzyme that converts phenylalanine (an amino acid) from food into tyrosine. In our country, it is obligatory to perform a screening test for phenylketonuria (Guthri test) on the 3rd day of life. In the neonatal unit, blood is collected on a tissue paper and sent to a designated laboratory. If the Guthri test is positive, the diagnosis should be confirmed in a specialist center and it should be made before 2 months of age. This enables effective treatment already in the asymptomatic period – eliminating phenylalanine from the diet, which prevents progressive brain damage. In this case, the prognosis is good.
The condition of the baby in the first days after birth is usually not of concern. Symptoms appear about 3 months old. psychomotor development is delayed, there are eczema rashes, sometimes vomiting. The urine of children with phenylketonuria has the so-called A “mousy” smell. Other symptoms include: hyperactivity, convulsions, and decreased muscle tone. Children with untreated phenylketonuria (IQ) are lowered.
Other recessive disorders include:
– mental retardation
– congenital deafness
— mukopolisacharydozy
– spinal muscle atrophy
Text: lek. med. Roma Roemer-Ślimak