Vitamin PP

Etiology and mechanisms of hypovitaminosis development

The development of vitamin PP hypovitaminosis is caused by two main etiological factors. First and foremost, this is a significant and prolonged deficiency of vitamin PP itself in the patient's daily diet. The second, equally important cause is a lack of tryptophan. This amino acid acts as a direct precursor from which this vitamin can be endogenously synthesized in the human body. When any of these components is lacking, metabolic pathways are disrupted, which inevitably leads to pronounced clinical manifestations.

Clinical presentation: pellagra syndrome

The main and most specific deficiency syndrome is pellagra. The name of the disease itself comes from the Italian word pelleagra, which literally translates as "rough skin". The clinical manifestations of pellagra are diverse, but they are traditionally divided into three major groups of lesions.

1. Lesions of the gastrointestinal tract and mucous membranes. Patients experience a painful burning sensation in the oral cavity. Ulcerations form on the oral mucosa, and severe stomatitis and gingivitis develop. The pathological process involves the tongue, stomach, and intestines, accompanied by debilitating diarrhea. The pathogenesis of these disorders lies in a sharp decrease in the formation of hydrochloric acid and the enzyme pepsin in the stomach, as well as a critical drop in the activity of digestive enzymes in the intestine.
2. Dermatological manifestations. A specific dermatitis develops, which ultimately leads to pronounced skin hypotrophy. A characteristic feature is the localization of lesions predominantly in areas of the body exposed to direct sunlight. This is explained by the fact that nicotinic acid deficiency causes severe skin photosensitivity. The process begins with peeling, after which hyperkeratosis and persistent pigmentation form in the zones of erythema (redness).
3. Neurological and psychiatric disorders. The central nervous system is extremely sensitive to vitamin deficiency. At initial stages, patients suffer from profound depression, may experience visual and auditory hallucinations, and develop acute psychoses. In the most severe and advanced cases, the disease progresses to dementia—severe acquired mental deterioration.

Approaches to deficiency treatment

Pellagra therapy requires immediate medical intervention. The basis of treatment is the administration of high doses of nicotinamide. A critically important aspect is the use of this drug in strict combination with other B-group vitamins. This tactic is dictated by the fact that the symptoms of deficiency of various vitamins in this group have a pronounced similarity, and isolated replenishment of only a single element may prove insufficiently effective due to cross-metabolic disorders.

Hypervitaminosis PP: causes and complications

In routine clinical practice, pathological excess of vitamin PP is quite rare. This is due to the fact that the excess of this water-soluble substance is excreted from the body quite quickly and efficiently with urine. However, a clinically significant condition can occur with prolonged and excessive intake of nicotinic acid specifically. It is important to note that the intake of nicotinamide does not lead to such toxic consequences.

The main manifestations of hypervitaminosis include:

• Non-specific vascular reaction. It manifests as marked hyperemia (redness) of the face and a subjective sensation of intense warmth. This is a direct consequence of intense vasodilation (widening of blood vessels).
• Allergic reactions. Various systemic manifestations of hypersensitivity may occur.
• Hepatotoxicity. With prolonged intake of unjustifiably high doses of the drug, serious liver dysfunction is possible. The pathogenesis of this complication consists in an excessive increase in the intracellular content of the coenzymes NAD and NADP, which in turn triggers a pathological increase in the activity of dehydrogenase enzymes.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Pathogenesis of the suppression of hydrochloric acid and pepsin secretion in the stomach during hypovitaminosis.
• Mechanisms of skin photosensitivity development in nicotinic acid deficiency.
• Biochemical role of excess NAD and NADP coenzymes in the mechanisms of hepatotoxicity.
• Interrelationship of tryptophan amino acid metabolism and the endogenous synthesis of vitamin PP.

Other topics in "Chapter 14. Vitamin Metabolism Disorders"

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