Page 316 - Robbins Basic Pathology by Vinay Kumar, Abul K. Abbas, Jon C. Aster
P. 316
302 C H A P T E R 7 Environmental and Nutritional Diseases • Marasmus is characterized by emaciation resulting from
loss of muscle mass and fat with relative preservation of
symptoms has not been borne out by controlled clinical serum albumin. It is caused by diets severely lacking in
studies. Such slight relief as may be experienced probably calories—both protein and nonprotein.
is a result of the mild antihistamine action of ascorbic acid.
The large excess of vitamin C is promptly excreted in the • Anorexia nervosa is self-induced starvation; it is charac-
urine but may cause uricosuria and increased absorption terized by amenorrhea and multiple manifestations of low
of iron, with the potential for iron overload. thyroid hormone levels. Bulimia is a condition in which
Other vitamins and some essential minerals are listed and food binges alternate with induced vomiting.
briefly described in Tables 7–9 and 7–10. Folic acid and
vitamin B12 are discussed in Chapter 11. • Vitamins A and D are fat-soluble vitamins with a wide
range of activities.Vitamin C and members of the vitamin
SUMMARY B family are water-soluble (Table 7–9 lists vitamin func-
Nutritional Diseases tions and deficiency syndromes).
• Primary PEM is a common cause of childhood deaths in Obesity
poor countries. The two main primary PEM syndromes
are marasmus and kwashiorkor. Secondary PEM occurs in In the United States, obesity has reached epidemic propor-
the chronically ill and in patients with advanced cancer (as tions. The prevalence of obesity increased from 13% to 34%
a result of cachexia). between 1960 and 2008, and as of 2009, 68% of Americans
between 20 and 75 years of age were overweight. Equally
• Kwashiorkor is characterized by hypoalbuminemia, gener- alarming, childhood obesity, a strong predictor of obesity
alized edema, fatty liver, skin changes, and defects in immu- in adults, also increased two- to three-fold over the same
nity. It is caused by diets low in protein but normal in period. Recent studies suggest that the epidemic of obesity
calories. also is rapidly spreading in developing countries such as
Table 7–9 Vitamins: Major Functions and Deficiency Syndromes
Vitamin Functions Deficiency Syndromes
Fat-Soluble A component of visual pigment Night blindness, xerophthalmia, blindness
Vitamin A Maintenance of specialized epithelia Squamous metaplasia
Maintenance of resistance to infection Vulnerability to infection, particularly measles
Vitamin D Rickets in children
Facilitates intestinal absorption of calcium and Osteomalacia in adults
Vitamin E phosphorus and mineralization of bone Spinocerebellar degeneration
Vitamin K Bleeding diathesis
Major antioxidant; scavenges free radicals
Dry and wet beriberi, Wernicke syndrome, Korsakoff
Cofactor in hepatic carboxylation of syndrome
procoagulants—factors II (prothrombin),VII,
IX, and X; and protein C and protein S Cheilosis, stomatitis, glossitis, dermatitis, corneal
vascularization
Water-Soluble As pyrophosphate, is coenzyme in
Vitamin B1 (thiamine) decarboxylation reactions Pellagra—“three Ds”: dementia, dermatitis, diarrhea
Vitamin B2 (riboflavin)
Converted to coenzymes flavin mononucleotide Cheilosis, glossitis, dermatitis, peripheral neuropathy
Niacin and flavin adenine dinucleotide, cofactors for Combined system disease (megaloblastic anemia and
many enzymes in intermediary metabolism
Vitamin B6 (pyridoxine) degeneration of posterolateral spinal cord tracts)
Vitamin B12 Incorporated into nicotinamide adenine
dinucleotide (NAD) and NAD phosphate; Scurvy
Vitamin C involved in a variety of oxidation–reduction Megaloblastic anemia, neural tube defects
Folate (redox) reactions No nonexperimental syndrome recognized
Pantothenic acid No clearly defined clinical syndrome
Biotin Derivatives serve as coenzymes in many
intermediary reactions
Required for normal folate metabolism and
DNA synthesis
Maintenance of myelinization of spinal cord
tracts
Serves in many redox reactions and
hydroxylation of collagen
Essential for transfer and use of one-carbon
units in DNA synthesis
Incorporated in coenzyme A
Cofactor in carboxylation reactions
