Primary immune thrombocytopenia or idiopathic thrombocytopenic purpura is a disease of autoimmune origin in which there is a low number of platelets, which puts patients at greater risk of bleeding.
The immune thrombocytopenia primary (ITP) is a disease of origin autoimmune. There is a low platelet count (which is known as thrombopenia or thrombocytopenia) due to increased platelet destruction and, to a lesser extent, a defect in their production. We say that it has an autoimmune origin since it is the patient’s immune system that produces antibodies that destroy platelets in the blood and prevent their production in the bone marrow. By having a low platelet count, patients are at greater risk of bleeding and possible hemorrhage. It can affect both children and adults.
At present, the term idiopathic or immune thrombocytopenic purpura remains in disuse and is called primary immune thrombocytopenia.
In other areas of the world, such as the United States, it is estimated that the incidence of ITP in adults is approximately six cases per 100,000 inhabitants. In the United Kingdom, the prevalence in adults is 1.6 per 100,000 people. What is clear is that the incidence of this disease is increasing in recent years.
Causes of primary immune thrombocytopenia (ITP)
Patients with ITP create autoantibodies that target the membrane of platelets and megakaryocytes (precursor cells of platelets present in the bone marrow), destroying platelets upon reaching the spleen and decreasing the production of platelets at the medullary level.
In most cases, the cause that triggers the production of autoantibodies against platelets is unknown, especially in adults. However, in children, ITP often occurs after viral infection or after vaccinations using live attenuated viruses.
There are other so-called secondary autoimmune thrombocytopenias where the cause is known, for example, associated with autoimmune diseases, common variable immunodeficiency, pregnancy, hepatitis C virus infection, or HIV infection. Autoimmune thrombocytopenia secondary to medications is also common.
Symptoms of ITP
How ITP presents, and its characteristic signs and the clinical development of the disease are highly variable, which significantly complicates the diagnosis, choice of the appropriate treatment, and the follow-up of patients affected by their disease—quality of life.
Those affected with primary immune thrombocytopenia may have no symptoms or may have hemorrhagic manifestations of varying severity, mainly depending on their platelet count.
The presence of petechiae is characteristic, which are small eruptions on the skin or mucous membranes, such as red or purple dots, caused by the leakage of red blood cells through the wall of the blood vessels. Petechiae do not disappear or bleach when compressed. This particularity differentiates them from other papular skin lesions that may be similar (such as those caused by insect bites, allergies, infections), which, due to superficial vasodilation, become white when compressed with the finger.
When the petechiae are more significant than 3 mm, they are called purpura, hence the name of this disease. Purpuric lesions larger than 1-2 cm are called ecchymoses, popularly known as bruises or bruises.
Petechiae, purpura, or ecchymosis appear more frequently in the lower third of the legs, as this is the part of the body where the blood vessels are subjected to more significant pressure. They can also appear after minor trauma.
In addition, there may be mucosal bleeding, such as nosebleeds (epistaxis), bleeding from the gums, or vaginal bleeding. More infrequently, more serious hemorrhages such as gastrointestinal, joint, or brain hemorrhages occur.