scurvy

Scurvy is a disease resulting from a deficiency of vitamin C, which is required for the synthesis of collagen in humans. The chemical name for vitamin C, ascorbic acid, is derived from the Latin name of scurvy, scorbutus, which also provides the adjective scorbutic ("of, characterized by or having to do with scurvy"). Scurvy leads to the formation of spots on the skin, spongy gums, and bleeding from the mucous membranes. The spots are most abundant on the thighs and legs, and a person with the ailment looks pale, feels depressed, and is partially immobilized. In advanced scurvy there are open, suppurating wounds and loss of teeth.

Scurvy was at one time common among sailors, pirates and others aboard ships at sea longer than perishable fruits and vegetables could be stored (subsisting instead only on cured and salted meats and dried grains) and by soldiers similarly separated from these foods for extended periods. It was described by Hippocrates (c. 460 BC–c. 380 BC), and herbal cures for scurvy have been known in many native cultures since prehistory. Scurvy was one of the limiting factors of marine travel, often killing large numbers of the passengers and crew on long-distance voyages. This became a significant issue in Europe from the beginning of the modern era in the Age of Discovery in the 15th century, continuing to play a significant role through World War I in the 20th century.

Today scurvy is known to be caused by a nutritional deficiency, but until the isolation of vitamin C and its direct link to scurvy in 1932, numerous theories and treatments were proposed, often on little or no experimental data. This inconsistency is attributed to the lack of vitamin C as a distinct concept, the varying vitamin C content of different foods (notably present in fresh citrus, watercress, and organ meat), and how vitamin C can be destroyed by exposure to air and copper.

Treatment by fresh food, particularly citrus fruit, was periodically implemented, as it had been since antiquity, but the ultimate cause of scurvy was not known until 1932, and treatment was inconsistent, with many ineffective treatments used into the 20th century. It was a Scottish surgeon in the British Royal Navy, James Lind who first proved it could be treated with citrus fruit in experiments he described in his 1753 book, A Treatise of the Scurvy,[1] though his advice was not implemented by the Royal Navy for several decades.

In infants, scurvy is sometimes referred to as Barlow's disease, named after Sir Thomas Barlow,[2] a British physician who described it. (N.B. Barlow's disease may also refer to mitral valve prolapse.) Other eponyms include Moeller's disease and Cheadle's disease.

Scurvy does not occur in most animals because they can synthesize their own vitamin C. However, humans and other higher primates (the simians and tarsiers), guinea pigs, most or all bats, and some species of birds and fish lack an enzyme necessary for such synthesis and must obtain vitamin C through their diet. Vitamin C is widespread in plant tissues, with particularly high concentrations occurring in citrus fruits (oranges, lemons, limes, grapefruits), tomatoes, potatoes, cabbages, and green peppers.

Cause

Scurvy or subclinical scurvy is caused by the lack of vitamin C. In modern Western societies, scurvy is rarely present in adults, although infants and elderly people are affected.[3] Vitamin C is destroyed by the process of pasteurization, so babies fed with ordinary bottled milk sometimes suffer from scurvy if they are not provided with adequate vitamin supplements. Virtually all commercially available baby formulas contain added vitamin C for this reason, but heat and storage destroy vitamin C. Human breast milk contains sufficient vitamin C, if the mother has an adequate intake.

Scurvy is one of the accompanying diseases of malnutrition (other such micronutrient deficiencies are beriberi or pellagra) and thus is still widespread in areas of the world depending on external food aid.[4] Though rare, there are also documented cases of scurvy due to poor dietary choices by people living in industrialized nations.[5][6][7][8]

Pathogenesis

Ascorbic acid is needed for a variety of biosynthetic pathways, by accelerating hydroxylation and amidation reactions. In the synthesis of collagen, ascorbic acid is required as a cofactor for prolyl hydroxylase and lysyl hydroxylase. These two enzymes are responsible for the hydroxylation of the proline and lysine amino acids in collagen. Hydroxyproline and hydroxylysine are important for stabilizing collagen by cross-linking the propeptides in collagen. Defective collagen fibrillogenesis impairs wound healing. Collagen is also an important part of bone, so bone formation is also affected. Defective connective tissue also leads to fragile capillaries, resulting in abnormal bleeding.

Prevention

Scurvy can be prevented by a diet that includes certain citrus fruits such as oranges or lemons. Other sources rich in vitamin C are fruits such as blackcurrants, guava, kiwifruit, papaya, tomatoes, bell peppers, and strawberries. It can also be found in some vegetables, such as carrots, broccoli, potatoes, cabbage, spinach and paprika. Some fruits and vegetables not high in vitamin C may be pickled in lemon juice, which is high in vitamin C. Many animal products, including liver, Muktuk (whale skin), and oysters, contain vitamin C. Though redundant in the presence of a balanced diet,[9] various nutritional supplements are available that provide ascorbic acid well in excess of that required to prevent scurvy, and even some candies and most soft drinks contain vitamin C as a preservative.