Disease Information for Osteomalacia

A condition marked by softening of the bones (due to impaired mineralization, with excess accumulation of osteoid), with pain, tenderness, muscular weakness, anorexia, and loss of weight, resulting from deficiency of vitamin D and calcium; This fat-soluble vitamin occurs mainly in two forms: ergocalciferol (activated ergosterol, vitamin D2), found in irradiated yeast; and cholecalciferol (activated 7-dehydrocholesterol, vitamin D3), formed in human skin by exposure to sunlight (ultraviolet radiation); In the liver, vitamin D3 is converted to 25(OH)D3, the major circulating form; It passes through the enterohepatic circulation and is reabsorbed from the gut. Principally in the kidneys, it is further hydroxylated to the much more metabolically active form, 1,25(OH)2D3 (1,25-dihydroxycholecalciferol, calcitriol, vitamin D hormone); The main function of vitamin D hormone is to increase calcium absorption from the intestine and promote normal bone formation and mineralization; Metabolic bone disease resulting from vitamin D deficiency is called rickets in children and osteomalacia in adults; Vitamin D deficiency may also be caused by defects in the production of 25(OH)D3 or the action of 1,25(OH)2D3; The deficiency may occur in in hereditary diseases, such as familial hypophosphatemic (vitamin D-resistant) rickets, an X-linked dominant disorder [Type II]; In children, changes include defective calcification of growing bone and hypertrophy of the epiphyseal cartilages; Epiphyseal cartilage cells cease to degenerate normally, but new cartilage continues to form, so that the epiphyseal cartilage becomes irregularly increased in width; Calcification then stops, and osteoid material accumulates around the capillaries of the diaphysis; The cancellous bone of the diaphysis and cortical bone may be resorbed in chronic deficiency; Adequate treatment with vitamin D permits calcium and phosphate deposition through degeneration of the cartilage cells; Osteoid material at the diaphysis ceases to form, and normal endochondral production of new bone is resumed; In adults, the changes are similar but are not confined to the ends of the long bones;aternal osteomalacia can lead to metaphyseal lesions and tetany in the newborn;

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