Homocystinuria

Homocystinuria is a genetically determined violation of the metabolism of the sulfur-containing amino acid methionine. For the first time this disease was described in 1962. Homocystinuria occurs with a frequency of 1 case per 50 000 to 250 000 newborns and is transmitted by an autosomal recessive type of inheritance. In the serum and especially the urine of people suffering from this disease, a large amount of the amino acid methionine, as well as a substance such as homocystin( normally not contained in human tissues and biological fluids), and a significant decrease in the content of the amino acid cystine.

The study of the effect of high concentrations of methionine and homocystin was carried out in animal experiments, which revealed the pathological effect of excess amounts of these substances on the body. Thus, an increase in the amount of homocystin in the serum leads to the formation of foci of tissue disintegration in the kidneys, spleen, gastric mucosa, bone system, vessels and other organs. The damaging effect of homocystine on the inner shell of the arteries, followed by the accumulation of platelets on it( blood plates involved in blood coagulation), was convincingly shown in experiments on baboons. The use of drugs that have the ability to prevent the formation of blood clots, does not lead to the restoration of the damaged inner shell of blood vessels. Similar changes were found in people with homocystinuria in the study of the sections of various tissues taken from them during life( hepatic, bone, etc.).It is known that the substance homocystine by activating a large number of chemical transformations in the human body contributes to the formation of thrombi in the blood vessels. Simultaneously, homocysteine ​​has poor solubility and can settle on the pathologically altered inner shell of blood vessels, thereby also creating conditions for the formation of blood clots in them. When studying the brain tissue of people who died from thrombosis of cerebral vessels with homocystinuria, tissue destruction sites were also found. Also, homocystinuria almost always occurs with the development of osteoporosis of bone tissue. The defeat of the eyes with homocystinuria consists in changes from the lens and eye muscles.

In homocystinuria, there is initially a disruption in the metabolism of the sulfur-containing amino acid methionine. Later, other types of metabolism are involved in the pathological process, which is one of the reasons for the development of all manifestations of the disease, which can affect quite different organs and systems of the human body.

Possible manifestations of homocystinuria are described by many researchers. At the same time, attention is drawn to the wide variety of symptoms of this disease. However, most authors believe that homocystinuria is characterized by a peculiar set of symptoms, which includes mental retardation with the formation of symptoms of the nervous system( manifestations depend on the level of damage to the nervous system), ectopic lenses, skeletal deformities, thromboembolism and cardiovascular damage. People who suffer from homocystinuria tend to have high growth, lean physique. They are characterized by long thin limbs, elongation of the fingers and feet, valgus position of the knee joints, various curvatures of the spine, funnel-shaped or keel-shaped deformations of the chest, moderately pronounced osteoporosis of the bone system. Due to the presence of osteoporosis in a person with homocystinuria, numerous fractures often occur with minor trauma. Along with this, there are descriptions of such forms of the disease, in which changes in the musculoskeletal system are minimal or absent altogether.

The most characteristic pathology on the part of the eyes in homocystinuria is the subluxation of the lens. In this case, as a rule, it shifts downwards. This feature is far from the last value in the recognition of this disease. However, in some cases, the lens may move in another direction. Owing to the displacement of the lens, secondary glaucoma often develops, which is characterized by a particularly malignant course and often progresses despite active treatment and repeated surgical interventions. Changes in the cardiovascular system in patients with homocystinuria are often found in violation of metabolic processes in the heart muscle and the development of thromboembolism in arterial vessels. Thromboembolism, as a rule, occurs at a young age( up to 30 years) and ends with a fatal outcome. The presence of thrombi in the vascular bed also explains the appearance of symptoms of damage to the nervous system( paralysis and paresis) and mental retardation.

Neuropsychic activity in homocystinuria is characterized by inertness( poor attention switching and low working capacity), a non-critical attitude to one's abilities, insufficient awareness of the environment, and a certain orientation prevails in the thinking of such people. Speech usually consists of short phrases, often with manifestations of dyslalia. Mimicry with this disease, as a rule, is poorly developed, sometimes there is an unmotivated smile. The coefficient of intellectual development corresponds at the same time to 32-72 units( at a rate of 85-115 units).

Diagnosis of homocystinuria is based on data on the presence of a similar disease in the brothers in the absence of symptoms in the parents of a sick person, on a combination of symptoms( subluxation of the lens, secondary glaucoma, changes in the musculoskeletal system, decreased intelligence, hemiparesis).An invaluable help in the recognition of the disease is the methods of laboratory diagnosis( biochemical, enzymatic, roentgeno-functional), which are conducted in specialized hospitals.

Homocystinuria has a constantly progressive nature of the course. At the same time in infants most often does not show a full set of signs of the disease. The defeat of the eyes and changes in the skeleton are formed, as a rule, not earlier than 3-5 years of age. Then, as the child grows, all the new signs gradually appear, and the disease goes to a more severe stage - the stage of decompensation, which is characterized by the development of secondary glaucoma, repeated strokes and many other symptoms.

Due to the fact that all manifestations of homocystinuria closely resemble those of Marfan syndrome( similar lesions of the eyes, musculoskeletal system), in some cases an incorrect diagnosis is made. Homocystinuria differs from Marfan's syndrome in the type of inheritance( in Marfan's syndrome it is autosomal dominant), more severe eye damage due to the development of secondary glaucoma, less lagging behind the growth of the child, lack of aortic aneurysm and valvular heart disease, less degree of "looseness"joints, flat feet, as well as the presence of osteoporosis. People suffering from homocystinuria are often blond or light-blond, with soft, slightly curly hair, blue eyes. In addition, the characteristic differences, in the form of the appearance of certain amino acids and the products of their metabolism in homocystinuria, can be detected during laboratory tests of blood serum. With Marfan's syndrome, such changes in blood composition are not detected.

Vitamin preparations are widely used in the treatment of homocystinuria. In some forms of the disease, quite good results have been obtained with vitamin B6 treatment. After applying relatively low doses of vitamin B6 on the fourth day of treatment, the metabolic disorders characteristic of homocystinuria disappear: homocystine is not detected in serum and urine, the amino acid content of methionine is reduced to normal, the level of the amino acid cystine is increased. But not always when treating this form of homocystinuria can be limited to the use of relatively small doses of vitamin B6.It is often necessary to resort to large doses of the drug, and the method to continue for several weeks. In a form of homocystinuria resistant to this method of treatment, the main method is a diet containing a minimum amount of the amino acid methionine. Basically, this is achieved due to a significant restriction of proteins of animal origin. Preference is given to products with a low content of methionine, which include cow, goat and women's milk, rice, oranges, tangerines, carrots, beets, potatoes, green peas, tomatoes, bananas, orange juice.

In the treatment of homocystinuria, small doses of soft-acting anti-clotting drugs and the formation of thrombi on the inner surface of blood vessels are also constantly being used. These drugs include all known acetylsalicylic acid( aspirin), which is taken daily in a low dosage determined by the doctor. There is also a treatment aimed at preventing the development of glaucoma or its elimination. In addition, if necessary, drugs that lower blood pressure, have an anti-inflammatory effect, improve the activity of the brain( nootropics), and also protect the liver( hepatoprotectors).According to the indications, repeated courses of massage and physiotherapy, laser acupuncture and reflexotherapy are prescribed. Much attention is paid to the treatment of chronic foci of infection, the resolution of questions about the timing of surgical treatment, as well as sanatorium treatment.

In recent years, the issues of dynamic dispensary monitoring of children with homocystinuria, as well as their closest relatives, are becoming especially topical. Targeted monitoring of sick children allows them to optimize their health status. At the same time, there is a definite positive dynamics in their physical development( it becomes more harmonious), some improvements in the neuropsychic state( activation of cognitive activity, improvement of auditory memory and voluntary attention) are revealed. In addition, attention is drawn to the decrease in the number of frequently ill children and the increase in the number of patients who are not ill during the year. Constant dispensary observation of such children helps stabilize the main pathological process, in favor of which is said to improve the state of the main organs and body systems.

Special attention is also paid to issues of social adaptation and vocational guidance. All observed pre-school children should attend specialized kindergartens for visually impaired children or be on an individual home basis. When they reach school age, they need to be trained in specialized support schools.

Parents of children with homocystinuria are advised to take soft-acting drugs regularly to prevent blood clots in the blood vessels( acetylsalicylic acid).