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Kashin–Beck disease (KBD) is a chronic, endemic osteochondropathy (disease of the bone), which is mainly distributed from northeastern to southwestern China involving 15 provinces.〔Yao, Y., Pei, F., Kang, P. (2011). Selenium, iodine, and the relation with Kashin–Beck disease. ''Nutrition'', 27, 1095–1100〕 Tibet currently has the highest incidence rate of KBD in China.〔 Southeast Siberia and North Korea are other affected areas〔 KBD usually involves children ages 5–15 and to date more than a million individuals have suffered from KBD.〔Wang, L.H., Fu, Y., Shi, Y.X., Wang, W.G. (2011). T-2 toxin induces degenerative articular changes in rodents: link to Kaschin–Beck disease. ''Toxicol Pathol'', 39, 502–507, p. 502–507.〕 The symptoms of KBD include joint pain, morning stiffness in the joints, disturbances of flexion and extension in the elbows, enlarged inter-phalangeal joints and limited motion in many joints of the body.〔Cao, J., Li, S., Shi, Z., Yue, Y., Sun, J., Chen, J., Fu, Q., Hughes., C.E., Caterson, B. (2008). Articular cartilage metabolism in patients with an endemic osteoarthropathy in China. Osteoarthritis and Cartilage, 16, 680–688.〕 Death of cartilage cells in the growth plate and articular surface is the basic pathologic feature; this can result in growth retardation and secondary osteoarthrosis.〔 Histological diagnosis of KBD is particularly difficult; clinical and radiological examinations have proved to be the best means for identifying KBD.〔Xiong, G. (2001). Diagnostic, clinical and radiological characteristics of Kashin–Beck disease in Shaanxi Province, PR China. ''Int Orthop'', 25, 147–150.〕 Little is known about the early stages of KBD before the visible appearance of the disease becomes evident in the destruction of the joints.〔 This disease has been recognized for over 150 years but its etiology has not yet been completely defined.〔 Currently the accepted potential causes of KBD include mycotoxins present in grain, trace mineral deficiency in nutrition and high levels of fulvic acid in drinking water.〔 Selenium and iodine have been considered the most important deficiencies associated with KBD.〔 Mycotoxins produced by fungi can contaminate grain which may cause KBD because mycotoxins cause the production of free radicals.〔 T-2 is the mycotoxin implicated with KBD, produced by members of several fungal genera.〔Wang, L.H., Fu, Y., Shi, Y.X., Wang, W.G. (2011). T-2 toxin induces degenerative articular changes in rodents: link to Kaschin–Beck disease. ''Toxicol Pathol'', 39, 502–507.〕 T-2 toxin can cause lesions in hematopoietic, lymphoid, gastrointestinal, and cartilage tissues, especially in physeal cartilage.〔 Fulvic acid present in drinking water damages cartilage cells.〔 Selenium supplementation in selenium deficient areas has been shown to prevent this disease.〔 However, selenium supplementation in some areas showed no significant effect, proving that deficiency of selenium may not be the dominant cause in KBD.〔 Recently a significant association between SNP rs6910140 of COL9A1 and Kashin–Beck disease was discovered genetically, suggesting a role of COL9A1 in the development of Kashin–Beck disease. ==Distribution == Kashin–Beck disease occurrence is limited to 13 provinces and two autonomous regions of China. It has also been reported in Siberia and North Korea, but incidence in these regions is reported to have decreased with socio-economic development. In China, KBD is estimated to affect some 2 million to 3 million people across China, and 30 million are living in endemic areas. Life expectancy in KBD regions has been reported to be significantly decreased in relation to selenium deficiency and Keshan disease (endemic juvenile dilative cardiomyopathia). The prevalence of KBD in Tibet varies strongly according to valleys and villages. Prevalence of clinical symptoms suggestive of KBD reaches 100% in 5- to 15-year-old children in at least one village. Prevalence rates of over 50% are not uncommon. A clinical prevalence survey carried out in Lhasa prefecture yielded a figure of 11.4% for a study population of approximately 50,000 inhabitants. As in other regions of China, farmers are by far the most affected population group. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Kashin–Beck disease」の詳細全文を読む スポンサード リンク
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