What are the other Names for this Condition? (Also known as/Synonyms)

• Heparin-Induced Thrombocytopaenia
• HIT (Heparin-Induced Thrombocytopenia)

What is Heparin-Induced Thrombocytopenia? (Definition/Background Information)

• Heparin-Induced Thrombocytopenia (HIT) is an adverse reaction of the body to heparin injections, administered intravenously or subcutaneously, resulting in decreased quantities of platelets in blood. The condition may be seen in about 1 in 20 cases of heparin-administered individuals and can be occasionally life-threatening
• Heparin is a blood-thinner (anticoagulant) medication that is administered in the treatment of thromboembolic disorders (clotting disorders such as deep vein thrombosis). Heparin is also prescribed as an effective prophylaxis towards preventing several other medical conditions
• Thrombocytopenia is a medical term used to describe a condition that results in decreased number of platelets in blood. The platelets are components of blood (or a type of blood cells) that help in clotting. The condition can cause spontaneous bleeding, excessive bleeding in response to a mild injury, red or purple spots on skin, and a propensity to bruising
• Heparin-Induced Thrombocytopenia may result in potentially severe complications if early detection and medical intervention is delayed. Discontinuation of heparin immediately on recognizing/diagnosing the condition can help in a complete resolution. In such cases, the prognosis of HIT is normally good

Who gets Heparin-Induced Thrombocytopenia? (Age and Sex Distribution)

• Heparin-Induced Thrombocytopenia is typically observed in individuals exposed to heparin for a period of less than a week or more (typically 4-10 days)
• The presentation of symptoms may occur at any age
• Both males and females may be affected, although the condition is marginally more common in females
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Heparin-Induced Thrombocytopenia? (Predisposing Factors)

• Exposure to heparin, which is used treat certain health issues, for a few days to weeks (usually between 4-10 days) is the primary risk factor for Heparin-Induced Thrombocytopenia

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Heparin-Induced Thrombocytopenia? (Etiology)

• Heparin-Induced Thrombocytopenia is caused by an immune reaction to a complex formed by platelet factor 4 (PF4) present in the body and the administered heparin
• The body’s immune system reacts to this complex by releasing abnormal autoantibodies that activate platelets, leading to thrombocytopenia (reduced blood platelets)

Generally, Heparin-Induced Thrombocytopenia develops 4-10 days after exposure to heparin. In some cases, a rapid loss in number of platelets is possible, if the individual has had prior exposure to heparin within the past 100 days. Alternatively, delayed onset is also possible, after heparin administration has already been discontinued.

What are the Signs and Symptoms of Heparin-Induced Thrombocytopenia?

Heparin-Induced Thrombocytopenia may be asymptomatic. The condition, by definition, indicates the following:

• Decrease in platelet count by 50% or more
• New blood clots (thrombosis) are observed to form during treatment with heparin - when this occurs, the blood condition is referred to as Heparin-Induced Thrombocytopenia and Thrombosis (HITT)

If an individual is symptomatic, the signs and symptoms may vary in type and severity, and include one or more of the following:

• Spontaneous bleeding (rare)
• Red or purple spots in the body, particularly on the lower legs
• Tendency for bruising
• Presence of blood in the urine and stool
• Excessive and unusual bleeding from the nose and mouth (bleeding from the gums)
• Unusually heavy menstrual flow in women
• Bleeding in the gastrointestinal tract, from the rectum
• Unusual level of bleeding after surgery
• Excess bleeding after dental work
• Bleeding inside the brain, which causes headache and other neurological symptoms 

In some individuals, skin signs and symptoms, such as blister formation and necrosis, may be noted. This condition is known as heparin-induced skin necrosis.

How is Heparin-Induced Thrombocytopenia Diagnosed?

Heparin-Induced Thrombocytopenia (HIT) is diagnosed on the basis of the following information:

• Complete physical examination and thorough medical history evaluation (including evaluating for heparin administration, current medications used, etc.)
• Assessment of the presenting signs and symptoms: The indicative features are referred to as the 4 “Ts”, namely thrombocytopenia, timing, thrombosis, and possibility of alternative/no other cause(s)
• Laboratory tests, including the HIT expert probability (HEP) scoring system, which tests for the following:
• Presence of anti PF4/heparin antibodies through ELISA
• Presence of pathologic platelet activating antibodies for confirmation (with serotonin-release assay or heparin-induced platelet activation test)
• Abdominal ultrasound imaging to examine for any spleen abnormalities
• Bone marrow test to check its health; this may include bone marrow aspiration and/or biopsy

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Heparin-Induced Thrombocytopenia?

The complications of Heparin-Induced Thrombocytopenia may include:

• Necrosis of skin at heparin injection site
• Anaphylactoid reactions (fever, low blood pressure, chest pain, labored breathing)
• Heart attack
• Pulmonary embolism
• Severe bleeding in the brain, which may be fatal (brain stroke)
• Unusual bleeding in the digestive tract
• Severe anemia, neurological abnormalities, and kidney failure

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Heparin-Induced Thrombocytopenia Treated?

The treatment for Heparin-Induced Thrombocytopenia may include one or more of the following, depending on the severity of signs and symptoms:

• Discontinuation of heparin
• If an anticoagulant medication is deemed necessary; then, the use of alternate medications such as warfarin, lepirudin, or non-heparin anti-factor Xa therapy
• Platelet transfusions: This may be performed in individuals, who are at a high risk for extensive and continuous bleeding

How can Heparin-Induced Thrombocytopenia be Prevented?

Heparin-Induced Thrombocytopenia may be preventable, by avoiding anti-coagulation medication containing heparin in some individuals.

What is the Prognosis of Heparin-Induced Thrombocytopenia? (Outcomes/Resolutions)

The prognosis of Heparin-Induced Thrombocytopenia is dependent upon the severity of the signs and symptoms and associated complications, if any noted.

• With correct diagnosis and prompt treatment, thrombocytopenia is reported to resolve within a week. In some cases, the recovery time may be longer
• Some affected individuals may have long-term post-thrombotic sequelae, which may result in limb amputation, permanent neurological damage, or bilateral adrenal hemorrhagic necrosis with adrenal failure
• In about 5-10% of those with complications, such as pulmonary embolism and heart attack, the condition can be fatal

Additional and Relevant Useful Information for Heparin-Induced Thrombocytopenia:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/blood-disorders/