Vitamin deficiencies with/without deficiency disease

Cobalamin-c disease remethylation of homocysteine to methionine also requires an activated form of vitamin B12. In the absence of normal B12 activation, homocystinuria results from a failure of normal vitamin B12 metabolism. Complementation analysis classifies defects in vitamin B12 metabolism into three groups cblC (most common), cblD and cblF. Most individuals become ill in the first few months or weeks of life with hypotonia, lethargy and growth failure. Optic atrophy and retinal changes can occur. Methylmalonate excretion is excessive, but less than in methylmalonyl-CoA mutase deficiency, and without ketoaciduria or metabolic acidosis. 

Medical personnel who work in affluent areas are unlikely to see large numbers of people with vitamin deficiency diseases. However, certain groups of the population are particularly at risk, such as low-income families and chronically ill patients. The classic symptoms of any vitamin deficiency disease as observed in laboratory animals are often blurred in humans. The clinical picture is often complicated by deficiencies of other vitamins, minerals, calories, and protein and by infections and parasite infestations, which usually accompany longstanding malnutrition. Biochemical, physiological, and behavioral changes can occur in the marginal deficiency state without or before the appearance of more specific symptoms. Since the nonspecificity of these changes makes them difficult to detail, this section focuses on the symptoms associated with individual vitamin deficiency diseases. 

Vitamin D is essential for bone formation. Without vitamin D, calcium and phosphorus could not be assimilated into the body or deposited onto the bones. In centuries past, deficiency of vitamin D caused a bone-softening disease called rickets in children and osteomalacia in adults. In this country, milk was fortified with vitamin D in the first half of the last century to put an end to the deficiency diseases, and it almost succeeded. Doctors still run into a case every now and then. 

With this one exception (the action of vitamin B12. in cyanide poisoning) the only certain chemotherapeutic action of vitamin B12 seems to be to correct the metabolic disorder which results from an existing deficiency of the vitamin. The effects, in terms of clinical improvement in pernicious anemia, for example, are remarkable, and much has been learned about the chemotherapeutic action of vitamin B12 by studying this disease. In other blood diseases—even in disorders so closely allied that the marrow is megaloblastic—vitamin B12 is without effect unless the disorder is due to lack of the vitamin. The same holds for diseases of the nervous system. The striking effect of vitamin B12 in subacute combined degeneration should not arouse false hopes that Bi2 will prove effective in cerebral, spinal, or neural disorders not due to deficiency of vitamin Bi2. 

This dietary deficiency disease is due to lack of the vitamin niacin or of the amino acid tryptophan (which is converted in the E)ody to nicotinic acid). It usually afflicts people whose dietary protein comes mainly from maize (corn) (which is deficient in both nicotinic acid and tryptophan). Also, it occurs in areas of India where the diet consists mainly of a millet called Jowar (Sorghum vulgare) without any animal foods. Some alcoholics and persons with disorders of abrsorp-tion have also been found to have the disease. 

Pure selenium deficiency, without concurrent vitamin E deficiency, is not generally seen except in animals on experimental diets (113). In China, selenium deficiency in humans has been associated with Keshan disease, a cardiomyopathy seen in children and in women of child-bearing ages, and Kashin-Beck disease, an endemic osteoarthritis in adolescents (113). 

Methionine synthase deficiency (cobalamin-E disease) produces homocystinuria without methylmalonic aciduria 677 Cobalamin-c disease remethylation of homocysteine to methionine also requires an activated form of vitamin B12 677 Hereditary folate malabsorption presents with megaloblastic anemia, seizures and neurological deterioration 678... 

This vitamin is not synthesized in animals, but rather it results from the bacterial or fungal fermentation in the rumen, after which it is absorbed and concentrated during metabolism. Among the known vitamins, this exclusive microbial synthesis is of great interest. One of the major results of vitamin Bn deficiency is pernicious anemia. This disease, however, usually does not result from a dietary deficiency of the vitamin, but rather by an absence of a glycoprotein ( gastric intrinsic factor ) in the gastric juices that facilitates absorption of the vitamin in the intestine. Control of the diseases hence is either by injection of Bn or by oral administration of the intrinsic factor, with or without the vitamin injection. 

Bile acids have two major functions in man (a) they form a catabolic pathway of cholesterol metabolism, and (b) they play an essential role in intestinal absorption of fat, cholesterol, and fat-soluble vitamins. These functions may be so vital that a genetic mutant with absence of bile acids, if at all developed, is obviously incapable of life, and therefore this type of inborn error of metabolism is not yet known clinically. A slightly decreased bile acid production, i.e., reduced cholesterol catabolism, as a primary phenomenon can lead to hypercholesterolemia without fat malabsorption, as has been suggested to be the case in familial hypercholesterolemia. A relative defect in bile salt production may lead to gallstone formation. A more severe defect in bile acid synthesis and biliary excretion found secondarily in liver disease causes fat malabsorption. This may be associated with hypercholesterolemia according to whether the bile salt deficiency is due to decreased function of parenchymal cells, as in liver cirrhosis, or whether the biliary excretory function is predominantly disturbed, as in biliary cirrhosis or extrahepatic biliary occlusion. Finally, an augmented cholesterol production in obesity is partially balanced by increased cholesterol catabolism via bile acids, while interruption of the enterohepatic circulation by ileal dysfunction or cholestyramine leads to intestinal bile salt deficiency despite an up to twentyfold increase in bile salt synthesis, to fat malabsorption, and to a fall in serum cholesterol. 

Alcoholics are the largest human group worldwide at risk of TDP deficiency due to their addictive life style eliminating sulficient supply vitamins and other micronutrients from the diet. Up to 80% of alcoholics were found to develop dilferent degrees of thiamine deficiency, many of them without any, or minimal, clinical manifestations. These appear usually in the advanced stages of alcoholic disease and are linked with the social, economic and physical deterioration of alfected persons (Butterworth 1989). 

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