Vitamin A deficiency neuropathy


Introduction to vitamin A deficiency neuropathy

Vitamin A deficiency (vitamine Adeficiency) is one of the world's four major nutritional deficiencies identified by the World Health Organization. Vitamin A deficiency can cause damage to the nervous system. Severe patients may have brain development retardation and myopathy, polyneuropathy or lethargy, etc. A deficiency can produce benign intracranial hypertension, mainly in the intake of food vitamin A deficiency, alcohol abuse, gastrointestinal malabsorption and congenital utilization of the liver and storage of vitamin A dysfunction.

basic knowledge

The proportion of illness: the incidence rate in children is about 1

Susceptible people: no special people

Mode of infection: non-infectious

Complications: respiratory infections, diarrhea


Vitamin A deficiency neuropathy

(1) Causes of the disease

Vitamin A deficiency is mainly seen in the intake of food vitamin A deficiency, alcohol abuse, gastrointestinal malabsorption and congenital utilization of the liver and storage of vitamin A dysfunction.

(two) pathogenesis

Vitamin A (37%):

Vitamin A is retinol, retinol is a natural and synthetic vitamin A isomer and derivative, vitamin A can be oxidized to retinal (vitamin A aldehyde), and retinal is the resynthesis group of all photosensitive visual pigments. The group is vital to vision. Its main oxidative metabolite is retinoic acid (vitamin A), which can be cleaved in the body to produce vitamin A. The carotenoids are called provitamin A, the most important of which is -carotene. .

Carotene (25%):

Carotene is mainly derived from plant foods such as carrots, sweet potatoes, yellow pumpkins, dark green leafy vegetables, yellow corn and tomatoes, some fruits are also rich in carotene, and ready-made vitamin A is derived from animal foods such as animal liver. Dairy products and fish are good sources of vitamin A. The concentration of vitamin A in cod liver oil is particularly high.

Alcoholism (17%):

Alcohol dehydrogenase is mainly involved in the action of alcohol in alcoholism, which causes the conversion of vitamin A to retinal. Zinc deficiency often coexists with alcoholism, hinders the mobilization of vitamin A, and the malabsorption caused by chronic alcoholism causes dietary carotene and The loss of vitamin A in the feces is increased. The long-term use of paraffin oil can be caused by the fat-soluble dissolution of vitamin A. Other cathartic agents allow food to pass through the intestine quickly, and the absorption in the intestine is reduced, causing vitamin A deficiency.

According to the recommendations of the World Food Organization and the World Health Organization, the daily intake of vitamin A is as follows: infants 350g, children aged 110 years, 400g, over 10 years old, 500-600g; breastfeeding mothers need large amounts, 850g (1g vitamins) A is equivalent to 3.3U, for infants, for example, the daily intake of vitamin A is 1100U), generally 1000g for adults and 800g for women. Vitamin A is stable to acid and alkali, but is easily destroyed by oxidation and ultraviolet rays. It is easy to be oxidized.

Vitamin A, also known as retinol, is a fat-soluble vitamin that has many important physiological functions.

1. Vitamin A is closely related to normal vision and photoreceptor cells, and once it is lacking, it can cause night blindness.

2. Vitamin A is related to the normal formation and function of human epithelial cells. There is a lack of eye dryness (dry eye disease) caused by decreased secretion of tears and corneal epithelial tissue. Further development can become corneal softening and ulceration. And perforation, leading to blindness.

3. Vitamin A can improve the body's immune function, so it is called "anti-infective vitamin", vitamin A deficiency, the body's barrier resistance to pathogenic microorganisms is reduced, and respiratory and digestive tract diseases are increased.

4. Vitamin A can promote growth and bone development. Vitamin A deficiency causes adolescent growth and development disorders, and reproductive function is affected.

5. Vitamin A is closely related to child mortality. Vitamin A supplementation in areas with vitamin A deficiency can reduce the mortality rate of children under 5 years of age by 23%, maternal mortality rate by 44%, and the mortality rate of vitamin A in children with measles. 50%.


Vitamin A deficiency neuropathy prevention

The fat in food is very important for the absorption of carotene. When eating vegetables, it is necessary to put some oil. Because of the high vitamin A content in the liver, some areas advocate giving the child a liver every week, which is very effective in preventing vitamin A and iron deficiency anemia. It works because the iron content in the liver is also high, and vitamin A and iron can promote absorption and utilization.


Vitamin A deficiency neuropathy complications Complications, respiratory infection, diarrhea

With the degree of deficiency of vitamin A, the severity of the disease is different, so the symptoms and signs are various, such as various manifestations of diseases such as respiratory infections and diarrhea.


Vitamin A deficiency neuropathy symptoms common symptoms diarrhea nausea corneal ulcer increased intracranial pressure dry skin sleepy night blindness

The role of vitamin A is mainly to maintain the visual function and normal differentiation of epithelial cells. Retinal is the re-synthesis group of all photosensitive visual pigments, which is essential for vision. Vitamin A is also necessary for growth, reproduction and life support.

Vitamin A deficiency can be divided into two categories:

1. Clinical vitamin A deficiency The early symptoms of this disease are night blindness. The time to distinguish objects after entering the low illumination environment from the bright place is prolonged. In severe cases, the object is completely invisible in the dark, called night blindness. Chronic alcoholism often falls at night. And traffic accidents may be related to potential night blindness.

Long-term severe vitamin A deficiency, in addition to night blindness, epithelial cells hyperkeratosis, a series of symptoms affecting the normal development of epithelial tissue, such as dry skin, dry conjunctiva, severe corneal dryness (dry eye disease), conjunctival temporal side There is Bitot plaque formation, which is caused by keratinocytes replacing the goblet cells secreted by the conjunctival epithelium and normal epithelial cells. There are clinical manifestations such as corneal ulcers or scars. According to estimates by the World Health Organization in 1994, the world has 2.8 million to 4 Older children have clinical vitamin A deficiency. In some developing countries, vitamin A deficiency is the main cause of blindness in adolescents. Excessive keratinization of mucosal epithelial cells can also be manifested as decreased secretion of lacrimal glands, parotid glands and gastric glands.

Decreased intake of -carotene and vitamin A-rich foods may be associated with an increased prevalence of lung cancer in epithelial cancer, especially in smokers. Severe patients may have brain developmental delay and myopathy, polyneuropathy or lethargy, etc. Vitamin A deficiency can produce a benign intracranial pressure increase.

2. Subclinical vitamin A deficiency, that is, vitamin A reduction in blood, without the above clinical manifestations, seemingly healthy population, it is estimated that there are 251 million children worldwide with subclinical vitamin A deficiency, although these children have no clinical manifestations of vitamin A deficiency, However, the resistance is low, growth retardation, prone to respiratory diseases and diarrhea and other diseases, and more serious, high mortality, and seriously endanger children's health.

Hypervitaminosis A: It is often caused by excessive intake of animal liver, cod liver oil, and candy or tablets containing vitamin A. It is characterized by headache, lethargy, nausea, vomiting, general weakness and dry skin.


Vitamin A deficiency neurological examination

Immunoassay for serum vitamin A content: normal 30 ~ 65g / dl, vitamin A intake is insufficient to reduce serum vitamin A levels, liver vitamin A reserves are almost completely depleted, serum vitamin A content decreased.

Conjunctival impression cytology is a new technique for early detection of corneal histology abnormalities.


Diagnosis and identification of vitamin A deficiency neuropathy

The diagnosis of this disease should investigate the intake of vitamin A in the diet, pay attention to diarrhea, infection and other diseases that increase vitamin A consumption, and make diagnosis based on the patient's symptoms, signs and dark adaptation reactions, and the speed of dark adaptation. The length and intensity of the light wave before entering the dark place are related to the irradiation time. If these conditions are fixed, the length of the dark adaptation time is negatively correlated with the nutritional status of vitamin A in the body. The more vitamin A is lacking, the longer the dark adaptation time is. .

Determination of serum vitamin A (normal 30 ~ 65g / dl) by immunoassay is helpful in the diagnosis.

Pay attention to the identification of other eye diseases, such as congenital amblyopia.

Was this article helpful?

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.