Acquired Coagulation Defects

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.