Hartnup's disease is a severe genetic disorder characterized by impaired amino acid metabolism. This disease is accompanied by beriberi, developmental delay, skin and neurological manifestations. How to recognize this pathology in a child? How is this anomaly inherited? In this article, we look at the causes, signs, and treatments for Hartnup's disease.
Etiology
Tryptophan is an essential amino acid that the body needs. A person can get this useful substance only through food. Tryptophan is absorbed in the intestines, and why is involved in the synthesis of nicotinic acid (vitamin B3).
The cause of Hartnup's disease is a mutation in the gene that is responsible for the metabolism of tryptophan. This is a congenital pathology that is inherited. There are two paths for the development of the disease:
- Due to a gene mutation, the absorption of tryptophan in the gastrointestinal tract worsens in a patient. Amino acidaccumulates in the intestine and interacts with bacteria. As a result of a biochemical reaction, toxic decay products are formed that poison the body. This has an extremely negative effect on the condition of the skin and nervous system.
- Due to a genetic defect, tryptophan is excreted in increased amounts in the urine. The body is deficient in this amino acid. This leads to a decrease in the synthesis of nicotinic acid and the development of beriberi. This affects the condition of the mucous membranes and skin, as well as the functioning of the digestive system.
Doctors also identify additional adverse conditions that can complicate the course of Hartnup's disease:
- deficiency of protein and vitamins in the diet;
- overwork;
- excessive sun exposure;
- emotional overstrain.
These factors can significantly worsen the patient's condition.
How pathology is inherited
The disease is transmitted in an autosomal recessive manner. This means that Hartnup disease is inherited only if the mutation is present in the genes of both parents.
Consider the probability of having a sick child:
- In half the cases, children become carriers of the damaged gene. They do not show signs of the disease, but there is a possibility of passing the pathology to offspring.
- 25% of babies are born sick.
- In 25% of cases, children are born he althy and do not carry the mutation.
This is a rather rare hereditary pathology. The disease occurs in 1 child in 24,000 newborns. In many cases, the parents of sick children were related by blood.
Symptomatics
Hartnup disease in children usually appears between the ages of 3 and 9. Sometimes the first signs of pathology are detected 10-14 days after birth and persist until adolescence. In adults, the signs of the disease are very weak or completely absent.
A symptom of Hartnup's disease is an increased sensitivity of the skin to ultraviolet light. Therefore, exacerbations of pathology are most often observed in the spring-summer period.
After exposure to ultraviolet rays, rashes appear on the skin, resembling a sunburn. The foci of inflammation have clear boundaries. Bubbles appear on reddened skin. The defeat of the epidermis is accompanied by itching and soreness. After healing, peeling and wrinkling of the skin is observed. Cracks can remain at the site of inflammation for a long time.
Skin damage is caused not only by exposure to ultraviolet radiation, but also by a deficiency of nicotinic acid. External manifestations of the pathology resemble signs of vitamin B3 deficiency (pellagra):
- On the hands and feet there is redness with clearly defined boundaries. It looks like "gloves" or "boots". Skin thickens and flakes.
- Red rashes in the shape of a "butterfly" can be seen on the child's face. They cover the wings of the nose and cheeks.
- The skin on the palms becomes yellowish and the fingers thicken.
- Inflammation appears not only on the skin, but also on the mucouslining of the mouth. The tongue swells and acquires a crimson color. The patient feels pain and burning in the mouth. There is increased salivation.
In most cases, the disease is accompanied by neurological symptoms:
- balance and coordination disorders;
- wobbly;
- shaking head, hands and eyeballs;
- headache;
- lowering the upper eyelid;
- sleep disorders;
- irritability;
- memory deterioration;
- mood swings.
Sick children have a slowdown in physical and mental development.
In some patients, vision deteriorates, strabismus may appear. In more rare cases, dyspeptic symptoms occur: diarrhea, nausea, loss of appetite. Patients lose weight for no reason and drastically.
These symptoms are not always observed, the pathology occurs in the form of periodic exacerbations. With age, episodes of the disease occur less and less often.
Diagnosis
The main method for diagnosing pathology is the study of urine and blood for biochemistry. In Hartnup's disease, the plasma levels of the following substances are significantly reduced:
- tryptophan;
- glycine;
- methionine;
- lysine.
At the same time, the concentration of the above amino acids in the urine increases dramatically.
This disease must be differentiated from pellagra. In primary forms of avitaminosis B3 is not observedamino acid metabolism disorders.
Therapy Methods
Patients are prescribed medications with vitamin B3 ("Nicotinamide", "Nicotinic acid"). It helps to fill the deficiency of this substance in the body.
The following groups of drugs are used as symptomatic therapy:
- Corticosteroid-based ointments ("Hydrocortisone", "Prednisolone"). These drugs are applied to the affected areas. Hormonal topical remedies help relieve inflammation and itching.
- Neuroleptics and antidepressants ("Fluoxetine", "Fevarin", "Neuleptil"). These drugs are indicated for irritability and mood swings.
- Sunscreens. These products help prevent breakouts and reduce skin photosensitivity. It is recommended to use creams with an additional anti-inflammatory effect.
Also, patients need to follow a special diet. Food should be rich in proteins and nicotinic acid. It is recommended to regularly include meat, liver, eggs, lean fish, and bran bread in the diet. It is useful to use brewer's yeast as a dietary supplement, this product contains a large amount of vitamin B3.
Prognosis, possible complications and prevention
The disease has a favorable prognosis. As the child grows older, the symptoms of pathology gradually decrease, and sometimes completely disappear. However, this does not mean that treatment is not necessary. If therapy is not available, the child may develop the following complications:
- psychosis;
- cognitive decline;
- cirrhosis of the liver;
- thinning skin;
- deterioration of vision.
Currently, the prevention of the disease has not been developed, because it is impossible to prevent gene mutations. Pathology is not detected with the help of prenatal screening. When planning a pregnancy, spouses are advised to visit a geneticist. This will help assess the risk of having a sick baby.
