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Factor XII deficiency is a deficiency in the production of factor XII (FXII), a plasma glycoprotein and clotting factor that participates in the coagulation cascade and activates factor XI. FXII appears to be not essential for blood clotting, as individuals with this condition are usually asymptomatic and form blood clots in vivo .
Factor XII deficiency is a rare disorder that is inherited in an autosomal recessive manner. [19] Unlike other clotting factor deficiencies, factor XII deficiency is totally asymptomatic and does not cause excess bleeding. [19] Mice lacking the gene for factor XII, however, are less susceptible to thrombosis. The protein seems to be involved in ...
Pernicious anemia is the most common cause of vitamin B 12 deficiency anemia in adults, which results from malabsorption of vitamin B 12 due to a lack or loss of intrinsic factor. [ 2 ] [ 8 ] There are relatively few studies which have assessed the impact of haematological measures in response to B 12 supplementation.
The body needs enough intrinsic factor to absorb and reabsorb vitamin B 12 from the bile, the lack of which reduces the time needed to develop a deficiency. [49] B 12 is required by enzymes for two reactions: the conversion of methylmalonyl-CoA to succinyl-CoA, and the conversion of homocysteine to methionine.
Factor XI (FXI) is produced by the liver and circulates as a homo-dimer in its inactive form. [9] The plasma half-life of FXI is approximately 52 hours. The zymogen factor is activated into factor XIa by factor XIIa (FXIIa), thrombin, and FXIa itself; due to its activation by FXIIa, FXI is a member of the "contact pathway" (which includes HMWK, prekallikrein, factor XII, factor XI, and factor IX).
Intrinsic factor (IF) is a glycoprotein, with a molecular weight of 45 kDa. In the duodenum, the free vitamin B 12 attaches to the intrinsic factor (IF) to create a vitamin B 12 –IF complex. This complex then travels through the small bowel and reaches the terminal tertiary portion of the small intestine, called the ileum.
In general, the most common cause of this condition is a deficiency of vitamin B 12. This may be due to a dietary deficiency, malabsorption in the terminal ileum, lack of intrinsic factor secreted from gastric parietal cells, or low gastric pH inhibiting attachment of intrinsic factor to ileal receptors. [10]
Fibrinogen deficiency, also known as factor I deficiency, is a rare inherited bleeding disorder related to fibrinogen function in the coagulation cascade. It is typically subclassified into four distinct fibrinogen disorders : afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and hypodysfibrinogenemia.