Pathophysiology of Blood Disorders: Hemostasis and Bleeding Disorders

Comprehensive vocabulary flashcards covering the pathophysiology of hemostasis, including primary/secondary hemostasis, vascular and platelet purpuras, coagulopathies, and hypercoagulability states based on the lecture notes from the University of Medicine and Pharmacy 'Victor Babeş' Timişoara.

Primary Hemostasis

The totality of mechanisms responsible for the spontaneous cessation of bleeding following small vessel injury, involving vascular and platelet phases to form a "white" platelet thrombus.

Secondary Hemostasis

The process of coagulation involving plasmatic factors that results in the formation of a "red" fibrin thrombus or clot.

Von Willebrand Factor (vWF)

A multimeric protein produced by the endothelium and megakaryocytes that facilitates platelet adhesion and transports/stabilizes factor VIII, increasing its half-life in circulation.

Prothrombinase Complex

A functional unit consisting of $Xa + Va + Ca^{2+} + PL$ (platelet phospholipid) that converts prothrombin into thrombin (IIa).

Antithrombin III (AT III)

A soluble plasma inhibitor that inactivates factors IIa, Xa, XIIa, XIa, and IXa; its effect is accelerated 1000-fold by heparin.

Plasmin

The active effector of the fibrinolysis system that dissolves existing fibrin clots and produces fibrin degradation products (FDP) and D-dimers.

Petechiae

Pinpoint cutaneous-mucous hemorrhages resulting from superficial localization in small vessels like arterioles and capillaries.

Hereditary Hemorrhagic Telangiectasia (Rendu-Osler-Weber syndrome)

An autosomal dominant genetic disorder of capillary angiogenesis characterized by dilated, tortuous small blood vessels with thin walls that bleed easily.

Henoch-Schonlein Purpura (Anaphylactoid purpura)

A generalized IgA-mediated vasculitis involving small vessels of the skin, GI tract, kidneys, and joints, typically occurring after an upper respiratory tract infection.

Thrombocytopenia

A condition defined as a decrease in the number of platelets below $100,000/mm^3$, with spontaneous hemorrhages occurring when levels drop below $20,000/mm^3$.

Idiopathic Thrombocytopenic Purpura (ITP)

An autoimmune disorder (Type II Hypersensitivity) where IgG anti-platelet autoantibodies against GP IIb:IIIa or GP Ib lead to platelet destruction by the reticuloendothelial system.

Heparin Induced Thrombocytopenia (HIT)

A condition occurring in less than $5\%$ of patients treated with unfractionated heparin, caused by IgG antibodies against heparin–PF4 complexes, leading to platelet aggregation and thrombi.

Thrombotic Thrombocytopenic Purpura (TTP)

A severe disorder characterized by widespread small vessel occlusion by platelet-rich microthrombi, often due to a deficiency in the metalloprotease ADAMTS 13.

Bernard-Soulier Syndrome

An autosomal recessive platelet adhesion defect caused by a deficit of GP Ib, which acts as the receptor for von Willebrand factor.

Glanzmann Thrombasthenia

An autosomal recessive platelet aggregation defect caused by a deficit of GP IIb-IIIa, which acts as the receptor for fibrinogen.

Hemophilia A

An X-linked recessive disorder characterized by a deficiency in coagulation factor VIII, primarily affecting males.

Hemophilia B

A rare X-linked recessive congenital bleeding disorder characterized by a deficiency or dysfunction of coagulation factor IX.

Vitamin K

A liposoluble factor required for the $\gamma$-carboxylation of glutamic acid in vitamin K-dependent factors II, VII, IX, and X to enable them to bind $Ca^{2+}$.

Disseminated Intravascular Coagulation (DIC)

A systemic activation of coagulation causing diffuse thrombosis and consumption of platelets and clotting factors, followed by a secondary activation of fibrinolysis.

Factor V Leiden

A mutation of the factor V gene that results in a modified factor V resistant to inactivation by activated protein C (aPC), leading to increased thrombin generation and venous thrombosis risk.