The most common conditions associated with thrombophilia are deep vein thrombosis (DVT) and pulmonary embolism (PE), which are referred to collectively as venous thromboembolism (VTE). DVT usually occurs in the legs, and is characterized by pain, swelling and redness of the limb. It may lead to long-term swelling and heaviness due to damage to valves in the veins. The clot may also break off and migrate (embolize) to arteries in the lungs. Depending on the size and the location of the clot, this may lead to sudden-onset shortness of breath, chest pain, palpitations and may be complicated by collapse, shock and cardiac arrest.

Venous thrombosis may also occur in more unusual places: in the veins of the brain, liver (portal vein thrombosis and hepatic vein thrombosis), mesenteric vein, kidney (renal vein thrombosis) and the veins of the arms. Whether thrombophilia also increases the risk of arterial thrombosis (which is the underlying cause of heart attacks and strokes) is less well established.

Thrombophilia has been linked to recurrent miscarriage, and possibly various complications of pregnancy such as intrauterine growth restriction, stillbirth, severe pre-eclampsia and abruptio placentae.

Protein C deficiency may cause purpura fulminans, a severe clotting disorder in the newborn that leads to both tissue death and bleeding into the skin and other organs. The condition has also been described in adults. Protein C and protein S deficiency have also been associated with an increased risk of skin necrosis on commencing anticoagulant treatment with warfarin or related drugs.

Thrombophilia can be congenital or acquired. "Congenital thrombophilia" refers to inborn conditions (and usually hereditary, in which case ""hereditary thrombophilia"" may be used) that increase the tendency to develop thrombosis, while, on the other hand, "acquired thrombophilia" refers to conditions that arise later in life.

Common signs and symptoms of DVT include pain or tenderness, swelling, warmth, redness or discoloration, and distention of surface veins, although about half of those with the condition have no symptoms. Signs and symptoms alone are not sufficiently sensitive or specific to make a diagnosis, but when considered in conjunction with known risk factors, can help determine the likelihood of DVT. In most suspected cases, DVT is ruled out after evaluation, and symptoms are more often due to other causes, such as cellulitis, Baker's cyst, musculoskeletal injury, or lymphedema. Other differential diagnoses include hematoma, tumors, venous or arterial aneurysms, and connective tissue disorders.

Phlegmasia cerulea dolens is a very large and dangerous type of DVT. It is characterized by an acute and almost total venous occlusion of the entire extremity outflow, including the iliac and femoral veins. The leg is usually painful, tinged blue in color, and swollen, which may result in venous gangrene.

Paget-Schroetter disease is the obstruction of an upper extremity vein (such as the axillary vein or subclavian vein) by a thrombus. The condition usually comes to light after vigorous exercise and usually presents in younger, otherwise healthy people. Men are affected more than women.

Deep vein thrombosis (DVT) is the formation of a blood clot within a deep vein. It most commonly affects leg veins, such as the femoral vein. Three factors are important in the formation of a blood clot within a deep vein—these are the rate of blood flow, the thickness of the blood and qualities of the vessel wall. Classical signs of DVT include swelling, pain and redness of the affected area.

Deep vein thrombosis (DVT), is the formation of a blood clot in a deep vein, most commonly the legs. Symptoms may include pain, swelling, redness, or warmth of the affected area. About half of cases have no symptoms. Complications may include pulmonary embolism, as a result of detachment of a clot which travels to the lungs, and post-thrombotic syndrome.

Risk factors include recent surgery, cancer, trauma, lack of movement, obesity, smoking, hormonal birth control, pregnancy and the period following birth, antiphospholipid syndrome, and certain genetic conditions. Genetic factors include deficiencies of antithrombin, protein C, and protein S, and factor V Leiden mutation. The underlying mechanism typically involves some combination of decreased blood flow rate, increased tendency to clot, and injury to the blood vessel wall.

Individuals suspected of having DVT may be assessed using a clinical prediction rule such as the Wells score. A D-dimer test may also be used to assist with excluding the diagnosis or to signal a need for further testing. Diagnosis is most commonly confirmed by ultrasound of the suspected veins. Together, DVT and pulmonary embolism are known as venous thromboembolism (VTE).

Anticoagulation (blood thinners) is the standard treatment. Typical medications include low-molecular-weight heparin, warfarin, or a direct oral anticoagulant. Wearing graduated compression stockings may reduce the risk of post-thrombotic syndrome. Prevention may include early and frequent walking, calf exercises, aspirin, anticoagulants, graduated compression stockings, or intermittent pneumatic compression. The rate of DVTs increases from childhood to old age; in adulthood, about one in 1000 adults are affected per year. About 5% of people are affected by a VTE at some point in time.

Nine in ten people with sinus thrombosis have a headache; this tends to worsen over the period of several days, but may also develop suddenly (thunderclap headache). The headache may be the only symptom of cerebral venous sinus thrombosis. Many patients have symptoms of stroke: inability to move one or more limbs, weakness on one side of the face or difficulty speaking. This does not necessarily affect one side of the body as in the more common "arterial" stroke.

40% of people have seizures, although it is more common in women who develop sinus thrombosis peripartum (in the period before and after giving birth). These are mostly seizures affecting only one part of the body and unilateral (occurring on one side), but occasionally the seizures are generalised and rarely they lead to status epilepticus (persistent or recurrent seizure activity for a long period of time).

In the elderly, many of the aforementioned symptoms may not occur. Common symptoms in the elderly with this condition are otherwise unexplained changes in mental status and a depressed level of consciousness.

The pressure around the brain may rise, causing papilledema (swelling of the optic disc) which may be experienced as visual obscurations. In severely raised intracranial pressure, the level of consciousness is decreased, the blood pressure rises, the heart rate falls and the patient assumes an abnormal posture.

A venous thrombus is a blood clot (thrombus) that forms within a vein. "Thrombosis" is a term for a blood clot occurring inside a blood vessel. A common type of venous thrombosis is a deep vein thrombosis (DVT), which is a blood clot in the deep veins of the leg. If the thrombus breaks off (embolizes) and flows towards the lungs, it can become a pulmonary embolism (PE), a blood clot in the lungs.

An inflammatory reaction is usually present, mainly in the superficial veins and, for this reason this pathology is called most of the time thrombophlebitis. The inflammatory reaction and the white blood cells play a role in the resolution of venous clots.

The initial treatment for venous thromboembolism is typically with either low molecular weight heparin (LMWH) or unfractionated heparin. LMWH appears to have lower rates of side effects; however, both result in similar rates of survival.

Superficial venous thromboses cause discomfort but generally not serious consequences, as do the deep venous thromboses (DVTs) that form in the deep veins of the legs or in the pelvic veins. Nevertheless, they can progress to the deep veins through the perforator veins or, they can be responsible for a lung embolism mainly if the head of the clot is poorly attached to the vein wall and is situated near the sapheno-femoral junction.

When a blood clot breaks loose and travels in the blood, this is called a venous thromboembolism (VTE). The abbreviation DVT/PE refers to a VTE where a deep vein thrombosis (DVT) has moved to the lungs (PE or pulmonary embolism).

Since the veins return blood to the heart, if a piece of a blood clot formed in a vein breaks off it can be transported to the right side of the heart, and from there into the lungs. A piece of thrombus that is transported in this way is an "embolus": the process of forming a thrombus that becomes embolic is called a "thromboembolism". An embolism that lodges in the lungs is a "pulmonary embolism" (PE). A pulmonary embolism is a very serious condition that can be fatal depending on the dimensions of the embolus. Venous thromboembolism (VTE) refers to both DVTs and PEs.

Systemic embolisms of venous origin can occur in patients with an atrial or ventricular septal defect, through which an embolus may pass into the arterial system. Such an event is termed a paradoxical embolism.

Coagulopathy may cause uncontrolled internal or external bleeding. Left untreated, uncontrolled bleeding may cause damage to joints, muscles, or internal organs and may be life-threatening. People should seek immediate medical care for serious symptoms, including heavy external bleeding, blood in the urine or stool, double vision, severe head or neck pain, repeated vomiting, difficulty walking, convulsions, or seizures. They should seek prompt medical care if they experience mild but unstoppable external bleeding or joint swelling and stiffness.

Hypercoagulability in pregnancy is the propensity of pregnant women to develop thrombosis (blood clots). Pregnancy itself is a factor of hypercoagulability (pregnancy-induced hypercoagulability), as a physiologically adaptive mechanism to prevent "post partum" bleeding. However, when combined with an additional underlying hypercoagulable states, the risk of thrombosis or embolism may become substantial.

Coagulopathy (also called a bleeding disorder) is a condition in which the blood’s ability to coagulate (form clots) is impaired. This condition can cause a tendency toward prolonged or excessive bleeding (bleeding diathesis), which may occur spontaneously or following an injury or medical and dental procedures. Of note, coagulopathies are sometimes erroneously referred to as "clotting disorders"; a clotting disorder is a predisposition to clot formation (thrombus), also known as a hypercoagulable state or thrombophilia.

Findings of tenderness, induration, pain and/or erythema along the course of a superficial vein usually establish a clinical diagnosis, especially in patients with known risk factors. In addition, there is often a palpable, sometimes nodular cord, due to thrombus within the affected vein. Persistence of this cord when the extremity is raised suggests the presence of thrombus.

Cerebral venous sinus thrombosis (CVST) is the presence of acute thrombosis (a blood clot) in the dural venous sinuses, which drain blood from the brain. Symptoms may include headache, abnormal vision, any of the symptoms of stroke such as weakness of the face and limbs on one side of the body, and seizures. The diagnosis is usually by computed tomography (CT/CAT scan) or magnetic resonance imaging (MRI) employing radiocontrast to demonstrate obstruction of the venous sinuses by thrombus.

Treatment is with anticoagulants (medication that suppresses blood clotting), and rarely thrombolysis (enzymatic destruction of the blood clot). Given that there is usually an underlying cause for the disease, tests may be performed to look for these. The disease may be complicated by raised intracranial pressure, which may warrant surgical intervention such as the placement of a shunt.

Pregnancy-induced hypercoagulability is probably a physiologically adaptive mechanism to prevent "post partum" hemorrhage. Pregnancy changes the plasma levels of many clotting factors, such as fibrinogen, which can rise up to three times its normal value. Thrombin levels increase. Protein S, an anticoagulant, decreases. However, the other major anticoagulants, protein C and antithrombin III, remain constant. Fibrinolysis is impaired by an increase in plasminogen activator inhibitor-1 (PAI-1 or PAI) and plasminogen activator inhibitor-2 (PAI-2), the latter synthesized from the placenta. Venous stasis may occur at the end of the first trimester, due to enhanced compliance of the vessel walls by a hormonal effect.

Also, pregnancy can cause hypercoagulability by other factors, e.g. the prolonged bed rest that often occurs "post partum" that occurs in case of delivery by forceps, vacuum extractor or Caesarean section.

A study of more than 200,000 women came to the result that admission to inpatient care during pregnancy was associated with an 18-fold increase in the risk of venous thromboembolism (VTE) during the stay, and a 6-fold increase in risk in the four weeks after discharge, compared with pregnant women who did not require hospitalization. The study included women admitted to hospital for one or more days for reasons other than delivery or venous thromboembolism.

Pregnancy after the age of 35 augments the risk of VTE, as does multigravidity of more than four pregnancies.

Pregnancy in itself causes approximately a five-fold increased risk of deep venous thrombosis. Several pregnancy complications, such as pre-eclampsia, cause substantial hypercoagulability.

Hypercoagulability states as a pre-existing condition in pregnancy include both acquired ones, such as antiphospholipid antibodies, and congenital ones, including factor V Leiden, prothrombin mutation, proteins C and S deficiencies, and antithrombin III deficiency.

Superficial vein thrombosis extension to the deep vein system and/or recurrence of SVT.

Suppurative thrombophlebitis is suspected when erythema extends significantly beyond the margin of the vein and is likely to be associated with significant fever. If suspected, antibiotic treatment, surgical drainage and potentially vein excision are indicated.

Venous thromboembolism can occur with superficial vein thrombosis. Estimates of the percentage of patients with SVT who also have DVT vary between 6% and 53%, and symptomatic pulmonary embolism has been reported in 0% to 10% of patients with SVT.

Renal vein thrombosis (RVT) is the formation of a clot in the vein that drains blood from the kidneys, ultimately leading to a reduction in the drainage of one or both kidneys and the possible migration of the clot to other parts of the body. First described by German pathologist Friedrich Daniel von Recklinghausen in 1861, RVT most commonly affects two subpopulations: newly born infants with blood clotting abnormalities or dehydration and adults with nephrotic syndrome. Nephrotic syndrome, a kidney disorder, causes excessive loss of protein in the urine, hypoalbuminemia, hypercholesterolemia and edema, triggering a hypercoagulable state and increasing chances of clot formation. Other less common causes include hypercoagulable state, cancer, renal transplantation, behcet syndrome, antiphospholipid antibody syndrome or blunt trauma to the back or abdomen. Treatment of RVT mainly focuses on preventing further blood clots in the kidneys and maintaining stable renal function. The use of anticoagulants has become the standard treatment in treating this abnormality. Membranous Glomerulonephritis, the most common cause for nephrotic syndrome in adults, peaks in people ages 40–60 years old and It is twice as likely to occur in men than in women. Since nephrotic syndrome is the most common cause of RVT, people over 40 years old and men are most at risk to develop a renal vein thrombosis.

Prothrombin G20210A ( rs1799963) refers to condition in which a specific gene mutation increases the risk of blood clots.

The "G20210A" refers to the fact that the mutation is a guanine (G) to adenine (A) substitution at position 20210 of the DNA of the prothrombin gene. This mutation (or more accurately, single-nucleotide polymorphism or variant), is commonly associated with increased risk of occurrence and recurrence of the disease venous thromboembolism (VTE), including both deep vein thrombosis (DVT) and pulmonary embolism (PE). As of 2005, it was believed that most carriers of the mutation never develop VTE in their lifetimes. Other blood clotting pathway mutations that increase the risk of clots include factor V Leiden.

Prothrombin G20210A was identified in the 1990s, is almost exclusively present in Caucasians. It is estimated to have originated in that population slightly over 20,000 years ago. About 2 to 3% of Caucasians carry the variant.

Superficial vein thrombosis (SVT) is a type of venous thrombosis, or a blood clot in a vein, which forms in a superficial vein near the surface of the body. Usually there is thrombophlebitis, which is an inflammatory reaction around a thrombosed vein, presenting as a painful induration with erythema. SVT has a limited clinical significance (in terms of morbidity and mortality) when compared to a deep vein thrombosis (DVT), which occurs deeper in the body, at the deep venous system level. If the blood clot is too near from the sapheno-femoral junction there is a bigger risk of pulmonary embolism.

An estimated 64 percent of patients with venous thromboembolism may have activated protein C resistance.

Aside from the occasional flank or lower back pain caused by a sudden clot in the major veins to the kidneys, RVT produces few symptoms. Some patients may not display any symptoms while other patients may experience bloody urine, decrease in urine output, edema and worsening proteinuria. Usually the diagnoses of RVT is first made when a nephrotic syndrome patient experiences a pulmonary embolism or a sudden decrease in renal function or renal failure. These symptoms may vary in duration since a blood clot can resolve itself, but precautions should be taken to prevent the migration of the clot to other parts of the body. The most severe complication of RVT is a pulmonary embolism, caused by a clot, also called a thrombus, that originates from the renal vein or any other vein in the body and migrates to the pulmonary artery. A pulmonary embolism is a serious condition because; it can damage the lungs due to pulmonary hypertension and cause low blood oxygen, damaging other organs in the body. This condition can cause death if left untreated; about 30% percent of patients who have a pulmonary embolism will die, usually within one hour.

Infants and young children experiencing dehydration induced RVT, may experience dehydration symptoms (dry mouth, low urine output, loss of skin turgidity) as while as vomiting, nausea and fever, and the usual RVT symptoms like flank pain, blood in the urine, anaemia, edema, enlarged kidneys and kidney failure.

The acute syndrome presents with rapidly progressive severe upper abdominal pain, yellow discoloration of the skin and whites of the eyes, liver enlargement, enlargement of the spleen, fluid accumulation within the peritoneal cavity, elevated liver enzymes, and eventually encephalopathy. The fulminant syndrome presents early with encephalopathy and ascites. Liver cell death and severe lactic acidosis may be present as well. Caudate lobe enlargement is often present. The majority of patients have a slower-onset form of Budd–Chiari syndrome. This can be painless. A system of venous collaterals may form around the occlusion which may be seen on imaging as a "spider's web". Patients may progress to cirrhosis and show the signs of liver failure.

On the other hand, incidental finding of a silent, asymptomatic form may not be a cause for concern.

Signs and symptoms of PTS in the leg may include:

- pain (aching or cramping)

- heaviness

- itching or tingling

- swelling (edema)

- varicose veins

- brownish or reddish skin discoloration

- ulcer

These signs and symptoms may vary among patients and over time. With PTS, these symptoms typically are worse after walking or standing for long periods of time and improve with resting or elevating the leg.

PTS lowers a person's quality of life after DVT, specifically with regards to physical and psychological symptoms and limitations in daily activities.

The Trousseau sign of malignancy or Trousseau's syndrome is a medical sign involving episodes of vessel inflammation due to blood clot (thrombophlebitis) which are recurrent or appearing in different locations over time (thrombophlebitis migrans or migratory thrombophlebitis). The location of the clot is tender and the clot can be felt as a nodule under the skin. Trousseau's syndrome is a rare variant of venous thromboembolism (VTE) that is characterized by recurrent, migratory thrombosis in superficial veins and in uncommon sites, such as the chest wall and arms. This syndrome is particularly associated with pancreatic, gastric and lung cancer and Trousseau's syndrome can be an early sign of cancer

, sometimes appearing months to years before the tumor would be otherwise detected. Heparin therapy is recommended to prevent future clots. The Trousseau sign of malignancy should not be confused with the Trousseau sign of latent tetany caused by hypocalcemia.

Post-thrombotic syndrome (PTS), also called postphlebitic syndrome and venous stress disorder is a medical condition that may occur as a long-term complication of deep vein thrombosis (DVT).