Many cases of congenital dysfibrinogenemia are asymptomatic. Since manifestations of the disorder generally occur in early adulthood or middle-age, younger individuals with a gene mutation causing it may not have had time to develop symptoms while previously asymptomatic individuals of advanced age with such a mutation are unlikely to develop symptoms. Bleeding episodes in most cases of this disorder are mild and commonly involve easy bruising and menorrhagia. Less common manifestations of bleeding may be severe or even life-threatening; these include excessive bleeding after tooth extraction, surgery, vaginal birth, and miscarriage. Rarely, these individuals may suffer hemarthrosis or cerebral hemorrhage. In one study of 37 individuals >50 years old afflicted with this disorder, 19% had a history of thrombosis. Thrombotic complications occur in both arteries and veins and include transient ischemic attack, ischemic stroke, myocardial infarction, retinal artery thrombosis, peripheral artery thrombosis, and deep vein thrombosis. In one series of 33 individuals with a history of thrombosis due to congenital dysfibrinogenemia, five developed chronic pulmonary hypertension due to ongoing pulmonary embolism probably stemming form deep vein thrombosis. About 26% of individuals with the disorder suffer both bleeding and thrombosis complications.

Individuals with congenital hypfibringenemia often lack any symptoms are detected by routine lab testing of fibrinogen or when tested for it because close relatives have symptomatic hypofibrinogenmeia. Indeed, studies indicate that, among family members with the identical congenital hypofibrinogenemia mutation, some never exhibit symptoms and those that are symptomatic develop symptoms only as adults.

Symptoms usually present from the period of birth to early childhood as: nose bleeds, bruising, and/or gum bleeding. Problems later in life may arise from anything that can cause internal bleeding such as: stomach ulcers, surgery, trauma, or menstruation. Abnormality of the abdomen, Epistaxis, Menorrhagia, Purpura, Thrombocytopenia, and prolonged bleeding time have also been listed as symptoms of various Giant Platelet Disorders.

Individuals with this disorder are usually less symptomatic than patients with other fibrinogen disorders because their fibrinogen levels are generally sufficient to prevent spontaneous bleeding. Those with particularly low blood fibrinogen levels (<0.5 gram/liter) may develop serious bleeding spontaneously and many with the disorder do so following trauma or surgery. Depending on their fibrinogen levels, women with the disorder may also bleed excessively during delivery and the postpartum period; in rare cases, they may have an increased risk of suffering miscarriages. Individuals with the disorder also suffer thrombotic events which may include blockage of large arteries in relatively young patients who have high levels of cardiovascular risk factors. The thrombi which form in these individuals are unstable, tend to embolize, and may therefore lead to thromboembolic events such as pulmonary embolism. Both bleeding and thrombotic events can occur at separate times or even concurrently in the same individual with the disorder.

The signs and symptoms of TTP may at first be subtle and nonspecific. Many people experience an influenza-like or diarrheal illness before developing TTP. Neurological symptoms are very common and vary greatly in severity. Frequently reported symptoms include feeling very tired, confusion, and headaches. Seizures and symptoms similar to those of a stroke can also be seen.

As TTP progresses, blood clots form within small blood vessels (microvasculature), and platelets (clotting cells) are consumed. As a result, bruising, and rarely bleeding can occur. The bruising often takes the form of purpura, while the most common site of bleeding, if it occurs, is from the nose or gums. Larger bruises (ecchymoses) may also develop.

The classic presentation of TTP includes a constellation of five medical signs which classically support the clinical diagnosis of TTP, although it is unusual for patients to present with all 5 symptoms. The pentad includes:

- Fever

- Changes in mental status

- Thrombocytopenia

- Reduced kidney function

- Haemolytic anaemia (microangiopathic hemolytic anemia).

High blood pressure (hypertension) may be found on examination.

In of study of 32 individuals diagnoses with hypodysfibrinogenemia, 41% presented with episodic bleeding, 43% presented with episodic thrombosis, and 16% were asymptomatic, being detected by abnormal blood tests. Bleeding and thrombosis generally begin in adulthood with the average age at the time of presentation and diagnosis being 32 years. Bleeding is more frequent and severe in women of child-bearing age; these women may suffer miscarriages, menometrorrhagia, and excessive bleeding during child birth and/or the postpartum period. Excessive bleeding following major or minor surgery, including dental extractions, occurs in both females and males with the disorder. Thrombotic complications of the disorder are often (~50%) recurrent and can involve central and peripheral arteries, deep and superficial veins. Thrombotic events may be serious and involve occlusion of a cerebral artery leading to stroke, splanchnic venous thrombosis, and pulmonary thrombosis presumptively secondary to deep vein thrombosis.

Bernard–Soulier syndrome often presents as a bleeding disorder with symptoms of:

Giant platelet disorders are rare disorders featuring abnormally large platelets, thrombocytopenia and a tendency to bleeding. Giant platelets cannot stick adequately to an injured blood vessel walls, resulting in abnormal bleeding when injured. Giant platelet disorder occurs for inherited diseases like Bernard-Soulier syndrome, gray platelet syndrome and May-Hegglin anomaly.

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.

The clinical presentation of TMA, although dependent on the type, typically includes: fever, microangiopathic hemolytic anemia (see schistocytes in a blood smear), renal failure, thrombocytopenia and neurological manifestations. Generally, renal complications are particularly predominant with Shiga-toxin-associated hemolytic uremic syndrome (STx-HUS) and atypical HUS, whereas neurologic complications are more likely with TTP. Individuals with milder forms of TTP may have recurrent symptomatic episodes, including seizures and vision loss. With more threatening cases of TMA, and also as the condition progresses without treatment, multi-organ failure or injury is also possible, as the hyaline thrombi can spread to and affect the brain, kidneys, heart, liver, and other major organs.

Characteristically, there is increased mucosal bleeding:

- menorrhagia

- easy bruising

- epistaxis

- gingival bleeding

- gastrointestinal bleeding

- postpartum bleeding

- increased bleeding post-operatively.

The bleeding tendency is variable but may be severe. Hemarthrosis, particularly spontaneous, is very rare, in contrast to the hemophilias.

Platelet numbers and morphology are normal. Platelet aggregation is normal with ristocetin, but impaired with other agonists such as ADP, thrombin, collagen or epinephrine.

The dysfibrinogenemias consist of three types of fibrinogen disorders in which a critical blood clotting factor, fibrinogen, circulates at normal levels but is dysfunctional. Congenital dysfibrinogenemia is an inherited disorder in which one of the parental genes produces an abnormal fibrinogen. This fibrinogen interferes with normal blood clotting and/or lyses of blood clots. The condition therefore may cause pathological bleeding and/or thrombosis. Acquired dysfibrinogenemia is a non-hereditary disorder in which fibrinogen is dysfunctional due to the presence of liver disease, autoimmune disease, a plasma cell dyscrasias, or certain cancers. It is associated primarily with pathological bleeding. Hereditary fibrinogen Aα-Chain amyloidosis is a sub-category of congenital dysfibrinogenemia in which the dysfunctional fibrinogen does not cause bleeding or thrombosis but rather gradually accumulates in, and disrupts the function of, the kidney.

Congenital dysfibrinogenmia is the commonest of these three disorders. Some 100 different genetic mutations occurring in more than 400 families have been found to cause it. All of these mutations as well as those causing hereditary fibrinogen Aα-Chain amyloidosis exhibit partial penetrance, i.e. only some family members with one of these mutant genes develop dysfibrinogenemia-related symptoms. While both of these congenital disorders as well as acquired dysfibrinogenemia are considered very rare, it is estimated that ~0.8% of individuals with venous thrombosis have either a congenital or acquired dysfibrinogenemia. Hence, the dysfibrinogenemia disorders may be highly under-diagnosed conditions due to isolated thrombotic events that are not appreciated as reflecting an underlying fibrinogen disorder.

Congenital dysfibrinogenemia is distinguished from a similar inherited disorder, congenital hypodysfibrinogenemia. Both disorders involve the circulation of dysfunctional fibrinogen but in congenital hypodysfibrinogenemia plasma fibrinogen levels are low while in congenital dysfibrinogenemia they are normal. Furthermore, the two disorders involve different gene mutations and inheritance patterns as well as somewhat different symptoms.

Thrombophilia (sometimes hypercoagulability or a prothrombotic state) is an abnormality of blood coagulation that increases the risk of thrombosis (blood clots in blood vessels). Such abnormalities can be identified in 50% of people who have an episode of thrombosis (such as deep vein thrombosis in the leg) that was not provoked by other causes. A significant proportion of the population has a detectable abnormality, but most of these only develop thrombosis in the presence of an additional risk factor.

There is no specific treatment for most thrombophilias, but recurrent episodes of thrombosis may be an indication for long-term preventative anticoagulation. The first major form of thrombophilia, antithrombin deficiency, was identified in 1965, while the most common abnormalities (including factor V Leiden) were described in the 1990s.

Glanzmann's thrombasthenia is an abnormality of the platelets. It is an extremely rare coagulopathy (bleeding disorder due to a blood abnormality), in which the platelets contain defective or low levels of glycoprotein IIb/IIIa (GpIIb/IIIa), which is a receptor for fibrinogen. As a result, no fibrinogen bridging of platelets to other platelets can occur, and the bleeding time is significantly prolonged.

Heparin may be used for both prevention and the treatment of thrombosis. It exists in two main forms: an "unfractionated" form that can be injected under the skin or through an intravenous infusion, and a "low molecular weight" form that is generally given subcutaneously (administered under the skin). Commonly used low molecular weight heparins are enoxaparin, dalteparin, nadroparin and tinzaparin.

In HIT, the platelet count in the blood falls below the normal range, a condition called thrombocytopenia. However, it is generally not low enough to lead to an increased risk of bleeding. Most people with HIT will therefore not experience any symptoms. Typically the platelet count will fall 5–14 days after heparin is first given; if someone has received heparin in the previous three months, the fall in platelet count may occur sooner, sometimes within a day.

The most common symptom of HIT is enlargement or extension of a previously diagnosed blood clot, or the development of a new blood clot elsewhere in the body. This may take the form of clots either in arteries or veins, causing arterial or venous thrombosis, respectively. Examples of arterial thrombosis are stroke, myocardial infarction ("heart attack"), and acute leg ischemia. Venous thrombosis may occur in the leg or arm in the form of deep vein thrombosis (DVT) and in the lung in the form of a pulmonary embolism (PE); the latter usually originate in the leg but migrate to the lung.

In those receiving heparin through an intravenous infusion, a complex of symptoms ("systemic reaction") may occur when the infusion is started. These include fever, chills, high blood pressure, a fast heart rate, shortness of breath, and chest pain. This happens in about a quarter of people with HIT. Others may develop a skin rash consisting of red spots.

The differential diagnosis for Bernard–Soulier syndrome includes both Glanzmann thrombasthenia and pediatric Von Willebrand disease. BSS platelets do not aggregate to ristocetin, and this defect is not corrected by the addition of normal plasma, distinguishing it from von Willebrand disease.

Thrombotic microangiopathy (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 atypical hemolytic uremic syndrome, disseminated intravascular coagulation, scleroderma renal crisis, malignant hypertension,

antiphospholipid antibody syndrome, and drug toxicities, e.g. calcineurin inhibitor toxicity.

Hypodysfibrinogenemia, also termed congenital hypodysfibrinogenemia, is a rare hereditary fibrinogen disorder cause by mutations in one or more of the genes that encode a factor critical for blood clotting, fibrinogen. These mutations result in the production and circulation at reduced levels of fibrinogen at least some of which is dysfunctional. Hypodysfibrinogenemia exhibits reduced penetrance, i.e. only some family members with the mutated gene develop symptoms.

The disorder is similar to a form of dysfibrinogenemia termed congenital dysfibrinogenemia. However, congenital dysfibrinogenemia differs form hypodysfibrinogenemia in four ways. Congenital dysfibrinogenemia involves: the circulation at normal levels of fibrinogen at least some of which is dysfunctional; a different set of causative gene mutations; a somewhat different mix of clinical symptoms; and a much lower rate of penetrance.

Hypodysfibrinogenemia causes episodes of pathological bleeding and thrombosis due not only to low levels of circulating fibrinogen but also to the dysfunction of a portion of the circulating fibrinogen. The disorder can lead to very significant bleeding during even minor surgical procedures and women afflicted with the disorderoften suffer significant bleeding during and after giving child birth, higher rates of miscarriages, and menorrhagia, i.e. abnormally heavy bleeding during the menstrual period.

The various types of vWD present with varying degrees of bleeding tendency, usually in the form of easy bruising, nosebleeds, and bleeding gums. Women may experience heavy menstrual periods and blood loss during childbirth.

Severe internal bleeding and bleeding into joints are uncommon in all but the most severe type, vWD type 3.

Thrombotic thrombocytopenic purpura (TTP) is a rare disorder of the blood-coagulation system, causing extensive microscopic clots to form in the small blood vessels throughout the body, resulting in low platelet counts. These small blood clots, called thrombi, can damage many organs including the kidneys, heart, brain, and nervous system. In the era before effective treatment with plasma exchange, the fatality rate was about 90%. With plasma exchange, this has dropped to 10% at six months. Because the disease generally results from antibodies that activate the immune system to inhibit the ADAMTS13 enzyme, agents that suppress the immune system, such as glucocorticoids, rituximab, cyclophosphamide, vincristine, or ciclosporin, may also be used if a relapse or recurrence follows plasma exchange. Platelets are not transfused unless the patient has a life-threatening bleed, since the transfused platelets would also quickly be consumed by thrombi formation, leading to a minimal increase in circulating platelets.

Most cases of TTP arise from autoantibody-mediated inhibition of the enzyme ADAMTS13, a metalloprotease responsible for cleaving large multimers of von Willebrand factor (vWF) into smaller units. The increase in circulating multimers of vWF increases platelet adhesion to areas of endothelial injury, particularly where arterioles and capillaries meet, which in turn results in the formation of small platelet clots called thrombi. As platelets are used up in the formation of thrombi, this then leads to a decrease in the number of overall circulating platelets, which may then cause life-threatening bleeds. The reason why the antibodies form is generally unknown for most patients, though it can be associated with some medications and autoimmune diseases such as HIV and Lupus, as well as pregnancy.

A rarer form of TTP, called Upshaw–Schulman syndrome, or "Inherited TTP," results from an autosomal recessive gene that leads to ADAMTS13 dysfunction from the time of birth, resulting in persisting large vWF multimers, which in turn results in the formation of thrombi (small platelet clots).

Red blood cells passing the microscopic clots are subjected to shear stress, which damages their membranes, leading to rupture of red blood cells within blood vessels, which in turn leads to anaemia and schistocyte formation. The presence of these blood clots in the small blood vessels reduces blood flow to organs resulting in cellular injury and end organ damage. Current therapy is based on support and plasmapheresis to reduce circulating antibodies against ADAMTS13 and replenish blood levels of the enzyme.

Heparin-induced thrombocytopenia (HIT) is the development of thrombocytopenia (a low platelet count), due to the administration of various forms of heparin, an anticoagulant. HIT predisposes to thrombosis (the abnormal formation of blood clots inside a blood vessel) because platelets release microparticles that activate thrombin, thereby leading to thrombosis. When thrombosis is identified the condition is called heparin-induced thrombocytopenia and thrombosis (HITT). HIT is caused by the formation of abnormal antibodies that activate platelets. If someone receiving heparin develops new or worsening thrombosis, or if the platelet count falls, HIT can be confirmed with specific blood tests.

The treatment of HIT requires stopping heparin treatment, and both protection from thrombosis and choice of an agent that will not reduce the platelet count any further. Several alternatives are available for this purpose and mainly used are danaparoid, fondaparinux, argatroban and bivalirudin.

While heparin was discovered in the 1930s, HIT was not reported until the 1960s.

Symptoms may differ greatly, as apparently modifiers control to some degree the amount of FVII that is produced. Some affected individuals have few or no symptoms while others may experience life-threatening bleeding. Typically this bleeding disorder manifests itself as a tendency to easy bruising, nose bleeding, heavy and prolonged menstruation, and excessive bleeding after dental or surgical interventions. Newborns may bleed in the head, from the umbilicus, or excessively after circumcision. Other bleeding can be encountered in the gut, in muscles or joints, or the brain. Hematuria may occur.

While in congenital disease symptoms may be present at birth or show up later, in patients with acquired FVII deficiency symptoms typically show up in later life.

About 3-4% of patients with FVII deficiency may also experience thrombotic episodes.

Thrombocytopenia usually has no symptoms and is picked up on a routine full blood count (or complete blood count). Some individuals with thrombocytopenia may experience external bleeding such as nosebleeds, and/or bleeding gums. Some women may have heavier or longer periods or breakthrough bleeding. Bruising, particularly purpura in the forearms and petechiae in the feet, legs, and mucous membranes, may be caused by spontaneous bleeding under the skin.

Eliciting a full medical history is vital to ensure the low platelet count is not secondary to another disorder. It is also important to ensure that the other blood cell types, such as red blood cells and white blood cells, are not also suppressed.

Painless, round and pinpoint (1 to 3 mm in diameter) petechiae usually appear and fade, and sometimes group to form ecchymoses. Larger than petechiae, ecchymoses are purple, blue or yellow-green areas of skin that vary in size and shape. They can occur anywhere on the body.

A person with this disease may also complain of malaise, fatigue and general weakness (with or without accompanying blood loss). Acquired thrombocytopenia may be associated with a history of drug use. Inspection typically reveals evidence of bleeding (petechiae or ecchymoses), along with slow, continuous bleeding from any injuries or wounds. Adults may have large, blood-filled bullae in the mouth. If the person's platelet count is between 30,000 and 50,000/mm, bruising with minor trauma may be expected; if it is between 15,000 and 30,000/mm, spontaneous bruising will be seen (mostly on the arms and legs).

Factor V Leiden (rs6025) is a variant (mutated form) of human factor V (one of several substances that helps blood clot), which causes an increase in blood clotting (hypercoagulability). With this mutation, the anticoagulant protein secreted (which normally inhibits the pro-clotting activity of factor V) is not able to bind normally to Factor V, leading to a hypercoagulable state, i.e., an increased tendency for the patient to form abnormal and potentially harmful blood clots. Factor V Leiden is the most common hereditary hypercoagulability (prone to clotting) disorder amongst ethnic Europeans. It is named after the Dutch city Leiden, where it was first identified in 1994 by Prof R. Bertina "et al."

Type 1 vWD (60-80% of all vWD cases) is a quantitative defect which is heterozygous for the defective gene. It can arise from failure to secrete vWF into the circulation or from vWF being cleared more quickly than normal. Decreased levels of vWF are detected at 20-50% of normal, i.e. 20-50 IU.

Many patients are asymptomatic or may have mild symptoms and not have clearly impaired clotting, which might suggest a bleeding disorder. Often, the discovery of vWD occurs incidentally to other medical procedures requiring a blood work-up. Most cases of type 1 vWD are never diagnosed due to the asymptomatic or mild presentation of type I and most people usually end up leading a normal life free of complications, with many being unaware that they have the disorder.

Trouble may, however, arise in some patients in the form of bleeding following surgery (including dental procedures), noticeable easy bruising, or menorrhagia (heavy menstrual periods). The minority of cases of type 1 may present with severe hemorrhagic symptoms.