Hartnup disease is a serious genetic pathology characterized by a violation of the metabolism of amino acids. This disease is accompanied by vitamin deficiency, developmental delay, skin and neurological manifestations. How to recognize this pathology in a child? And how is such an anomaly inherited? In this article, we will consider the causes, signs and methods of treating Hartnup 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 intestine, and why is it involved in the synthesis of nicotinic acid (vitamin B3).
The cause of Hartnup disease is a mutation in the gene that is responsible for tryptophan metabolism. This is a congenital pathology that is inherited. There are two ways to develop the disease:
- Due to a gene mutation, the absorption of tryptophan in the gastrointestinal tract worsens. Amino acid accumulates in the intestines and interacts with bacteria. As a result of the biochemical reaction, toxic decomposition products are formed that poison the body. This adversely affects the condition of the skin and nervous system.
- Due to genetic malfunction, tryptophan is excreted in increased quantities along with urine. A deficiency of this amino acid is formed in the body. This leads to a decrease in the synthesis of nicotinic acid and the development of vitamin deficiency. This affects the condition of the mucous membranes and skin, as well as the digestive system.
Doctors also identify additional adverse conditions that can complicate the course of Hartnup disease:
- deficiency of protein and vitamins in the diet;
- overwork;
- excessive exposure to the sun;
- emotional overstrain.
These factors can significantly worsen the condition of the patient.
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 two 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 chance of transmission of the pathology to offspring.
- In 25% of cases, a child is born sick.
- In 25% of cases, children are born healthy and are not carriers of mutations.
This is a rather rare hereditary pathology. The disease is observed in 1 child in 24,000 newborns. In many cases, the parents of sick children were in consanguinity.
Symptomatology
Hartnup disease in children usually occurs between the ages of 3 and 9 years. 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 mild or completely absent.
A symptom of Hartnup disease is an increased sensitivity of the skin to ultraviolet light. Therefore, exacerbations of pathology are most often noted in the spring-summer period.
After exposure to ultraviolet rays, rashes form on the skin that resemble 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 the signs of vitamin B3 deficiency (pellagra):
- Redness occurs on the hands and feet with clearly defined boundaries. It has the appearance of “gloves” or “boots”. The skin thickens and peels.
- On the face of the child you can see red rashes in the shape of a "butterfly". 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 mucous membrane of the mouth. The tongue swells and takes on a raspberry color. The patient feels pain and burning in the mouth. There is an increased separation of saliva.
In most cases, the disease is accompanied by neurological symptoms:
- disorders of balance and coordination of movements;
- shaky gait;
- trembling of the head, hands and eyeballs;
- headache;
- drooping of the upper eyelid;
- sleep disturbances;
- irritability;
- memory impairment;
- mood swings.
In sick children, a slowdown in physical and mental development is noted.
In some patients, vision deteriorates, strabismus may appear. In more rare cases, dyspeptic symptoms occur: diarrhea, nausea, loss of appetite. Patients for no reason and dramatically lose weight.
These symptoms are not observed constantly, the pathology proceeds in the form of periodic exacerbations. With age, episodes of the disease occur less and less.
Diagnostics
The main method for diagnosing pathology is the study of urine and blood for biochemistry. In Hartnup disease, the content of the following substances in plasma is significantly reduced:
- tryptophan;
- glycine;
- methionine;
- lysine.
In this case, the concentration of the above amino acids in the urine increases sharply.
This disease must be differentiated from pellagra. In the primary forms of vitamin B3 deficiency, there is no violation of amino acid metabolism.
Therapies
Patients are prescribed medications with vitamin B3 (Nicotinamide, Nicotinic Acid). This helps make up for the deficiency of this substance in the body.
The following groups of drugs are used as symptomatic therapy:
- Ointments based on corticosteroids ("Hydrocortisone", "Prednisolone"). These drugs are applied to the affected areas. Hormonal topical remedies help relieve inflammation and itching.
- Antipsychotics and antidepressants (Fluoxetine, Fevarin, Neuleptil). The use of such drugs is indicated for irritability and mood swings.
- Sunscreens These funds help prevent the appearance of rashes and reduce the photosensitivity of the skin. Creams with an additional anti-inflammatory effect are recommended.
Also, patients need to follow a special diet. Food should be rich in protein and nicotinic acid. It is recommended that you regularly include meat, liver, eggs, low-fat fish, and bran bread in the diet. It is good 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 a child grows up, the symptoms of pathology gradually decrease, and sometimes completely disappear. However, this does not mean that treatment does not need to be addressed. If there is no therapy, then the child may develop the following complications:
- psychoses
- cognitive decline;
- cirrhosis of the liver;
- thinning of the skin;
- visual impairment.
Currently, disease prevention has not been developed, because it is impossible to prevent gene mutations. Pathology is not detected using prenatal screening. When planning pregnancy, spouses are advised to visit a geneticist. This will help assess the risk of having a sick child.