immune thrombocytopenic purpura
Meaning of immune thrombocytopenic purpura: The immune system destroying its own platelets, leaving blood that clots poorly and skin that marks at the lightest knock.
Definition of immune thrombocytopenic purpura
Immune thrombocytopenic purpura is a disorder in which the immune system produces antibodies against a person's own platelets, the small blood fragments that plug injuries in vessel walls. Coated platelets are removed by the spleen, and their production in the bone marrow is impaired at the same time, so the count falls. Bruising, pinpoint skin spots and bleeding from gums or nose follow.
What does it look like?
The classic finding is petechiae: pinpoint red or purple spots, most often over the lower legs, that do not fade when pressed. Larger purple patches, which give the condition its old name, appear where small knocks would normally leave nothing. Bleeding from the gums, frequent nosebleeds, heavy menstrual periods and prolonged bleeding from minor cuts are common. Many people with a mildly reduced count have no symptoms at all and are identified through a blood test taken for another reason. Serious internal bleeding is uncommon but is the reason low counts are taken seriously.
How is it diagnosed?
By exclusion. There is no confirming test. The picture is a low platelet count with an otherwise normal blood cell count and a normal blood film apart from the shortage of platelets. Other causes are then ruled out: medicines that suppress or destroy platelets, infections including HIV and hepatitis C, lupus, lymphoma, liver disease, pregnancy, and a laboratory artifact in which platelets clump in the sample tube and the analyzer fails to count them. Bone marrow examination is not always needed and is reserved for atypical features.
How does it differ between children and adults?
| Feature | Children | Adults |
|---|---|---|
| Onset | Abrupt, often weeks after a viral illness | Usually gradual, with no preceding illness |
| Course | Most resolve without treatment within months | More often persists and needs treatment |
| Who is affected | Boys and girls equally | More often women, particularly in younger adulthood |
What is the name about?
It was once called idiopathic, meaning of unknown cause. Once the antibody mechanism was understood the initial was reinterpreted as immune. Many specialists now drop purpura entirely, since a large share of those affected never develop it, so the current preferred name is simply immune thrombocytopenia. It is a disorder of one blood component rather than a failure of the immune system as a whole.
Also known as
Used in a sentence
Immune thrombocytopenic purpura was diagnosed after other causes of a low platelet count were excluded.
Good to know
Many people with the condition never develop purpura, which is why the shorter name immune thrombocytopenia is preferred, and a low count is confirmed on a blood film because clumping in the sample tube produces a false result.
Word origin
Where “immune thrombocytopenic purpura” comes from
Thrombocytopenia joins the Greek thrombos, meaning clot, kytos, meaning cell, and penia, meaning lack; purpura is the Latin word for purple.