Etiology and Pathophysiology of Hypovitaminosis
The development of Vitamin PP deficiency is caused by two main etiological factors. First and foremost is a significant and prolonged deficit of Vitamin PP 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 the human body can endogenously synthesize the vitamin. When either of these components is lacking, metabolic pathways are disrupted, inevitably leading to pronounced clinical manifestations.
Clinical Presentation: Pellagra Syndrome
The primary and most specific deficiency syndrome is pellagra. The name of the disease originates from the Italian pelle agra, meaning "sour skin." The clinical manifestations of pellagra are diverse but are traditionally divided into three major categories of involvement.
- Gastrointestinal and Mucosal Involvement. Patients experience a painful burning sensation in the oral cavity. Ulcerations form on the oral mucosa, leading to severe stomatitis and gingivitis. The pathological process affects the tongue, stomach, and intestines, accompanied by debilitating diarrhea. The pathogenesis of these disorders lies in a sharp decrease in the production of hydrochloric acid and the enzyme pepsin in the stomach, as well as a critical drop in digestive enzyme activity in the intestines.
- Dermatological Manifestations. A specific dermatitis develops, leading to marked skin atrophy. A characteristic feature is the localization of lesions primarily on areas of the body exposed to direct sunlight. This is because nicotinic acid deficiency causes severe photosensitization of the skin. The process begins with desquamation, followed by the formation of hyperkeratosis and persistent pigmentation in areas of erythema (redness).
- Neurological and Psychiatric Disorders. The central nervous system is extremely sensitive to vitamin deficiency. In the early 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 — a severe acquired cognitive decline.
Approaches to Deficiency Treatment
Pellagra therapy requires immediate medical intervention. The mainstay of treatment is the administration of high doses of niacinamide. A crucial aspect is using this agent in strict combination with other B-complex vitamins. This strategy is dictated by the fact that the symptoms of various B-vitamin deficiencies overlap significantly, and isolated repletion of a single element may prove insufficiently effective due to cross-metabolic disruptions.
Hypervitaminosis PP: Causes and Complications
In routine clinical practice, pathological excess of Vitamin PP is relatively rare. This is because excess amounts of this water-soluble substance are excreted rapidly and efficiently by the kidneys in the urine. However, a clinically significant condition can occur with prolonged and excessive intake of nicotinic acid specifically. Notably, administration of niacinamide does not lead to such toxic consequences.
Key manifestations of hypervitaminosis include:
- Nonspecific vascular reaction. This presents as marked facial flushing (redness) and a subjective sensation of intense warmth. It is a direct consequence of intense vasodilation (widening of blood vessels).
- Allergic reactions. Various systemic hypersensitivity manifestations may occur.
- Hepatotoxicity. Prolonged intake of unjustifiably high doses of the drug can cause serious liver dysfunction. The pathogenesis of this complication involves an excessive increase in the intracellular content of NAD and NADP coenzymes, which in turn provokes a pathological elevation in dehydrogenase enzyme activity.