Acquired Coagulation Defects

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Disseminated intravascular coagulation (DIC) is an acquired coagulopathy that manifests as a paradoxical state of both excessive clotting and bleeding. This complex disorder results from the dysregulation of the coagulation and fibrinolytic systems. DIC is considered a ‘consumptive coagulopathy,’ meaning that both pro- and anti-coagulant components are rapidly consumed in the process, leading to a depletion of essential clotting factors and platelets.

The primary triggers for DIC include sepsis, particularly gram-negative sepsis caused by organisms like Neisseria meningitidis, which activates coagulation through bacterial proteins and lipopolysaccharides. Other significant causes include malignancies, notably acute promyelocytic leukemia, trauma, and obstetric complications. In DIC, exposure to procoagulant substances activates the coagulation cascade, leading to uncontrolled clot formation.

Clinically, DIC can present with platelet type bleeding such as petechiae, ecchymoses, and mucocutaneous bleeding. It can also result in more severe coagulopathy type bleeding, including gastrointestinal, genitourinary, or cerebral hemorrhages. Moreover, DIC can cause venous thrombi, most commonly DVTs in iliofemoral veins, sometimes accompanied by pulmonary emboli. This uncontrolled clotting can also lead to tissue & organ infarction due to arterial thrombi.

Diagnostic indicators for DIC include a prolonged PT, reflecting consumption of coagulation factors in the extrinsic pathway, and a prolonged aPTT, indicating involvement of the intrinsic pathway. Elevated D-dimer levels, a marker of fibrin degradation, are also commonly seen. Thrombocytopenia due to platelet consumption leads to a prolonged bleeding time. Additionally, schistocytes may be present on a peripheral blood smear, as these fragmented RBCs result from passage through small arteries clogged with fibrin clots.

Vitamin K deficiency is an acquired coagulopathy that significantly impacts the coagulation system. This deficiency affects a variety of vitamin K-dependent factors, including factors II, VII, IX, and X, as well as proteins C & S. These factors are essential for normal hemostasis, and their functional status is dependent on the availability of vitamin K as a cofactor for the enzyme ≥gamma-glutamyl carboxylase.

Vitamin K is primarily synthesized by colonic bacteria and can be obtained from dietary sources such as green leafy vegetables. It is activated by the liver enzyme epoxide reductase (VKOR), which allows it to serve its role as a cofactor for gamma-glutamyl carboxylase, subsequently activating vitamin K-dependent clotting factors.

Newborns are high-risk for vitamin K deficiency due the lack of intestinal flora that produce vitamin K, as well as inefficient hepatic utilization of the vitamin. This deficiency can lead to hemorrhagic disease of the newborn, a severe condition marked by intracranial and retroperitoneal bleeding, and potentially fatal outcomes. Since breast milk is low in vitamin K, newborns typically receive a vitamin K injection as a preventive measure. The risk of deficiency is notably higher in home births, mainly because this routine injection is often absent.

In adults, vitamin K deficiency can be caused by various factors. Malabsorption diseases such as inflammatory bowel disease and chronic pancreatitis reduce uptake of vitamin K. The use of antibiotics can disrupt gut flora responsible for vitamin K synthesis. Additionally, liver diseases like cirrhosis can impair the activation of vitamin K by epoxide reductase, resulting in deficiency.

Clinically, vitamin K deficiency manifests as a ‘coagulopathic’ type of bleeding. When mild, patients may experience easy bruising, epistaxis, and prolonged bleeding after injury. In severe cases, GI and genitourinary bleeding may occur. Diagnostically, vitamin K deficiency is commonly indicated by a prolonged PT, which results from decreased levels of factor VII affecting the extrinsic coagulation pathway. Treatment for vitamin K deficiency includes fresh frozen plasma (FFP) for severe cases and vitamin K supplementation for milder forms.

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What is disseminated intravascular coagulation (DIC) and what are its common triggers?

Disseminated intravascular coagulation (DIC) is an acquired coagulopathy characterized by both excessive clotting and bleeding due to activation of both the coagulation system and the fibrinolytic system. The most common triggers for DIC include sepsis, particularly gram-negative sepsis, malignancies like acute promyelocytic leukemia, trauma, and obstetric complications. These conditions expose the body to procoagulant substances, initiating the coagulation cascade.

What symptoms are associated with DIC?

DIC results in a condition called "consumptive coagulopathy," which depletes both clot-promoting and clot-inhibiting factors due to excessive activation of the coagulation system. This leads to two distinct types of bleeding: ‘platelet-type,’ marked by petechiae, ecchymoses, and mucocutaneous bleeding, and "coagulopathy-type," which involves bleeding in the gastrointestinal, genitourinary, or cerebral regions. Additionally, DIC can cause venous clots, most commonly deep vein thrombosis in the iliofemoral veins, and may result in tissue and organ damage due to arterial blockages.

What laboratory findings are indicative of DIC?

In DIC, laboratory tests often show prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT), reflecting the consumption of coagulation factors in the extrinsic and intrinsic pathways, respectively. Bleeding time is also prolonged due to thrombocytopenia. Other markers include elevated levels of D-dimer, a fibrin degradation product, and the presence of schistocytes, which are red blood cells damaged as they pass through small arteries clogged with fibrin clots.

What is vitamin K deficiency and how does it affect coagulation?

Vitamin K deficiency is a form of acquired coagulopathy that impairs the coagulation system. Vitamin K serves as a cofactor for gamma-glutamyl carboxylase, which activates vitamin K-dependent factors such as factors II, VII, IX, and X, as well as proteins C and S. A deficiency in vitamin K leads to impaired functioning of these factors, resulting in a tendency to bleed. This deficiency is particularly common in newborns and can also occur in adults due to malabsorption, prolonged antibiotic use, or liver diseases like cirrhosis.

How is vitamin K deficiency diagnosed and treated?

Vitamin K deficiency manifests as various types of bleeding, the severity of which depends on the extent of the deficiency. Laboratory tests usually show a prolonged PT due to decreased activation of the extrinsic pathway, specifically involving factor VII. Vitamin K supplementation is used to treat mild cases, while fresh frozen plasma, which contains all vitamin K-dependent factors, is administered in severe cases.