Thrombotic microangiopathies
Encyclopedia
Thrombotic microangiopathy, abbreviated TMA, is a pathology
that results in thrombosis
in capillaries and arterioles, due to an endothelial injury. It may be seen in association with thrombocytopenia
, anemia
, purpura
and renal failure
.
The classic TMAs are hemolytic uremic syndrome and thrombotic thrombocytopenic purpura
. Other conditions with TMA include disseminated intravascular coagulation
, scleroderma
renal crisis, malignant hypertension
,
antiphospholipid antibody syndrome, and drug toxicities, e.g. calcineurin inhibitor toxicity.
Bacterial toxins are the primary cause of one category of thrombotic microangiopathy known as HUS or hemolytic uremic syndrome. The another major category is TTP or thrombotic thrombocytopenic purpura
. It is caused by autoimmune or hereditary dysfunctions that activate the coagulation cascade or the complement system
.
Some sources group TTP and HUS together, while other sources express skepticism about their common pathophysiology.
, microangiopathic hemolytic anemia (see schistocytes in a blood smear), renal failure
, thrombocytopenia
, neurological manifestations.
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
that results in thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
in capillaries and arterioles, due to an endothelial injury. It may be seen in association with thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
, anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
, purpura
Purpura
Purpura is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin...
and renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
.
The classic TMAs are hemolytic uremic syndrome and thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura is a rare disorder of the blood-coagulation system, causing extensive microscopic thromboses to form in small blood vessels throughout the body...
. Other conditions with TMA include disseminated intravascular coagulation
Disseminated intravascular coagulation
Disseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
, scleroderma
Scleroderma
Systemic sclerosis or systemic scleroderma is a systemic autoimmune disease or systemic connective tissue disease that is a subtype of scleroderma.-Skin symptoms:...
renal crisis, malignant hypertension
Malignant hypertension
Malignant hypertension or hypertensive emergency is severe hypertension with acute impairment of an organ system and the possibility of irreversible organ-damage...
,
antiphospholipid antibody syndrome, and drug toxicities, e.g. calcineurin inhibitor toxicity.
Etiology
The etiology is dependent on the specific TMA.Bacterial toxins are the primary cause of one category of thrombotic microangiopathy known as HUS or hemolytic uremic syndrome. The another major category is TTP or thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura is a rare disorder of the blood-coagulation system, causing extensive microscopic thromboses to form in small blood vessels throughout the body...
. It is caused by autoimmune or hereditary dysfunctions that activate the coagulation cascade or the complement system
Complement system
The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime...
.
Some sources group TTP and HUS together, while other sources express skepticism about their common pathophysiology.
Presentation
The clinical presentation typically includes: feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, microangiopathic hemolytic anemia (see schistocytes in a blood smear), renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
, thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
, neurological manifestations.