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Imerslund–Gräsbeck syndrome, also known as Imerslund–Najman–Gräsbeck syndrome, Imerslund–Gräsbeck disease (IGS or INGS), Imerslund syndrome, congenital cobalamin malabsorption or autosomal recessive megaloblastic anemia (MGA1), is a rare autosomal recessive, familial form of vitamin B12 deficiency caused by malfunction of the "''Cubam''" receptor located in the terminal ileum. This receptor is composed of two proteins, amnionless (AMN), and cubilin. A defect in either of these protein components can cause this syndrome. This is a rare disease, with a prevalence about 1 in 200,000, and is usually seen in patients of European ancestry. Vitamin B12 is an important vitamin needed for bone marrow functioning, the deficit of which causes decreased marrow output and anemia. Vitamin B12 has two forms, one of which, along with folate, is important in DNA synthesis. Vitamin B12 is sensitive to acid deformation in the stomach, so a molecule called haptocorrin (R-factor), protects it in the stomach. In the small bowel, a molecule named intrinsic factor (IF), allows vitamin B12 to be absorbed in the ileum. IGS is caused by a mutation in the receptors located in the terminal portion of ileum. This is a very rare, and unlikely cause of vitamin B12 deficiency but is a cause nonetheless. ==Signs and symptoms== Defined as those seen in any macrocytic, megaloblastic anemia: *Anemia: causing fatigue, conjuctival pallor, pale complexion, and in some cases, a mild icterus (yellowing of the eye). *Glossitis ("shiny tongue"): shiny, glossy tongue. *Cheilosis (stomatitis): Inflammation of the edges of the lips and the oral mucosa. *Tabes dorsalis ("subacute combined degeneration of the spinal cord"): This involves the posterior section of the spinal cord and therefore involves proprioception (sense of position), touch, sense of vibration and in severe cases the lateral corticospinal tract, causing spastic paralysis of the limbs. * Peripheral neuropathy: tingling sensation in the arms and legs. * Pancytopenia: decreased number of blood cells of all lineages (RBCs,leucocytes,platelets), due to decreased bone marrow production. * Methylmalonyl CoA-emia: defined as blood having and unusually high concentration of methylmalonyl CoA. * Peripheral findings such as hypersegmented neutrophils and large RBCs on high field view of the blood smears. * Laboratory findings indicating increased MCV (Mean Corpuscular Volume), decreased Hgb/Hct (indicating anemia), and decreased value of vitamin B12 in the blood. * Proteinuria: protein found in the urine detected by analysis or by dipstick. * Reversal of all symptoms except neurological symptoms, by IV injection of vitamin B12. * Schilling test indicating no radioactive vitamin B12 in the urine. (This test has dropped out of favor and should not be tried in patients with any form of renal failure). 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「Imerslund–Gräsbeck syndrome」の詳細全文を読む スポンサード リンク
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