Insuficiencia Mitral

Idiopathic thrombocytopenic purpura

Idiopathic thrombocytopenic purpura (ITP) is the condition of having a low platelet count (thrombocytopenia) of no known cause (idiopathic). Platelets are small plateshaped bodies in the blood that combine to form a plug when a blood vessel is injured. As most causes appear to be related to antibodies against platelets, it is also known as immunethrombocytopenic purpura. Although most cases are asymptomatic, very low platelet counts can lead to a bleeding diathesis and purpura.
Purpura refers to a purplish or reddish-brown skin rash caused by the leakage of blood from broken capillaries into the skin. Other names for ITP include purpura hemorrhagica and essential thrombocytopenia.
ITP may be either acute or chronic. The acute form is mostcommon in children between the ages of two and six years; the chronic form is most common in adult females between 20 and 40. Between 10% and 20% of children with ITP have the chronic form. ITP does not appear to be related to race, lifestyle, climate, or environmental factors.
ITP is a disorder that affects the overall number of blood platelets rather than their function. The normal platelet levelin adults is between 150,000 and 450,000/mm3. Platelet counts below 50,000 mm3 increase the risk of dangerous bleeding from trauma; counts below 20,000/mm3 increase the risk of spontaneous bleeding.
The incidence of ITP is 50–100 new cases per million per year, with children accounting for half of that amount.
The male:female ratio in the adult group is 1:1.2–1.7 (for children it is 1:1) andthe median age of adults at the diagnosis is 56–60.
In adults, ITP is considered an autoimmune disorder, which means that the body produces antibodies that damage some of its own products--in this case, blood platelets. Some adults with chronic ITP also have other immune system disorders, such as systemic lupus erythematosus (SLE). In children, ITP is usually triggered by a virus infection, mostoften rubella, chickenpox, measles, cytomegalovirus, or Epstein-Barr virus. It usually begins about two or three weeks after the infection.
Acute ITP patients usually suffer from bruising; petechiae, nosebleeds and bleeding gums may occur if the platelet count is below 20,000, compared to a normal range of 150,000–400,000 per mm3. The bleeding may also occures from the skin or from the nose,mouth, digestive tract, or urinary tract. The onset is usually sudden. Bleeding into the skin takes the form of purpura or petechiae.
In extreme cases, patients with ITP may bleed into the lungs, brain, or other vital organs, leading to subarachnoid, intracerebral hemorrhage or other internal bleeding are very serious possible complications of this disease. Fortunately, these are unlikely inpatients with the platelets count above 20,000.
Chronic ITP has a gradual onset and may have minimal or no external symptoms. The low platelet count may be discovered in the course of a routine blood test. Most patients with chronic ITP, however, will consult their primary care doctor because of the purpuric skin rash, nosebleeds, or bleeding from the digestive or urinary tract. Women sometimes goto their gynecologist for unusually heavy or lengthy menstrual periods.
The risk factors for the development of chronic ITP include:
• female sex
• age over 10 years at onset of symptoms
• slow onset of bruising
• presence of other autoantibodies in the blood
Course of the disease
More than 70% of the cases in children end up in remission within 6 months whether treated or not.Moreover, a third of the remaining chronic cases remitted during the follow-up observation, and another third ended up with only mild thrombocytopenia (>50,000 platelets per μL). ITP is usually chronic in adults and the probability of durable remission is 20–40%.
Pathogenesis
In many cases, the cause is not actually idiopathic but autoimmune, with antibodies against platelets being detected...