Antithrombin (AT) is a small glycoprotein that inactivates several enzymes of the coagulation system. It is a 432-amino-acid protein produced by the liver. It contains three disulfide bonds and a total of four possible glycosylation sites. α-Antithrombin is the dominant form of antithrombin found in blood plasma and has an oligosaccharide occupying each of its four glycosylation sites. A single glycosylation site remains consistently un-occupied in the minor form of antithrombin, β-antithrombin. Its activity is increased manyfold by the anticoagulant drug heparin, which enhances the binding of antithrombin to factor IIa (prothrombin) and factor Xa. Nomenclature
Antithrombin is also termed antithrombin III (AT III). The designations antithrombin I through to antithrombin IV originate in early studies carried out in the 1950s by Seegers, Johnson and Fell.Antithrombin I (AT I) refers to the absorption of thrombin onto fibrin after thrombin has activated fibrinogen. Antithrombin II (AT II) refers to a cofactor in plasma, which together with heparin interferes with the interaction of thrombin and fibrinogen. Antithrombin III (AT III) refers to a substance in plasma that inactivates thrombin. Antithrombin IV (AT IV) refers to an antithrombin that becomes activated during and shortly after blood coagulation. Only AT III and possibly AT I are medically significant. AT III is generally referred to solely as "antithrombin" and it is antithrombin III that is discussed in this article. Structure
Antithrombin has a half-life in blood plasma of around 3 days.
Platyspondyly development begins with generalised osteosclerosis, then subsequent interspersing sclerotic bands develop within vertebral bodies with normal bone density, showing radiolucency. Diagnosis
Medical diagnosis of DSS involves various examinations and evaluations. This usually includes physical examinations, medical history evaluations, assessment of signs and symptoms, laboratory tests and image studies. Biopsy may also be required if necessary.Signs and symptoms of DSS show similarities with multifarious disorders and diseases such as osteosclerosis, H syndrome and Pyle disease. As such, it is likely that DSS is consequently incorrectly identified as osteopertrosis. Therefore, additional tests may be performed in order to arrive at a definitive diagnosis. Prognosis and management
Overall the disease has a poor prognosis, with treatment mainly focusing on palliation and comfort care.As the mechanism and clinical course of DSS remains unclear, definitive treatment is not available for patients. Bone marrow transplant may improve skeletal abnormalities, however it is improbable the transplant will ameliorate the unexplained neurological deteriorations. In addition, the surgery may not be suitable for every patients as the underlying genetic cause of the disease varies amongst patients. Advice of control and reduction in excessive calcium intake may be recommended by physicians to ensure circulating levels of parathyroid hormones are normal to induce and maintain bone resorption. == References ==