Idiopathic Thrombocytopenia P... Health Article

Definition

Idiopathic thrombocytopenic purpura (ITP) is a bleeding disorder caused by an abnormally low level of blood platelets, small disc-shaped cells essential to blood clotting (coagulation). ITP describes both the cause and symptoms of the condition: idiopathic means that the disorder has no apparent cause; thrombocytopenia refers to a decreased number of blood platelets; and purpura refers to a purplish or reddish-brown skin rash caused by the leakage into the skin of blood from broken capillaries. ITP is as of 2004 often called immune thrombocytopenic purpura rather than idiopathic because studies in the early 2000s have shown the presence of autoimmune antibodies in the blood. Other names for ITP include purpura hemorrhagica and essential thrombocytopenia.

Description

Coagulation, or clotting, is a complex process in which specific proteins found in blood plasma combine with other blood components, including platelets, to form clots and prevent blood loss. Platelets are tiny colorless disc-shaped cells in the blood that collect (aggregate) in blood vessels to form a plug when a vessel is injured. The platelet plug then binds coagulation proteins to form a clot that stops bleeding. A deficiency in platelets or a disorder that affects platelet production can disrupt clotting and severely complicate blood loss from accidental injury, surgery, and specific diseases or conditions in which bleeding can occur. ITP affects the overall number of blood platelets rather than their function. The normal platelet level in 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.

ITP may be either acute or chronic. The acute form occurs in children between ages two and six. Although chronic ITP is most common in adult females, 10 to 20 percent of children with ITP have the chronic form.

Demographics

Acute ITP affects children of both sexes between the ages of two and six years. The chronic form, although most common in adult females between the ages of 20 and 40, is found in 10 to 20 percent of children with ITP. ITP does not appear to be related to race, lifestyle, climate, or environmental factors.

Causes and symptoms

In children, ITP is usually triggered by a virus infection, most often rubella, chickenpox, measles, cytomegalovirus (CMV), or Epstein-Barr virus (EBV). ITP usually begins about two or three weeks after the infection.

Acute ITP is characterized by bleeding into 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. Purpura, a purplish or reddish-brown rash or discoloration of the skin, and petechiae, small round pinpoint hemorrhages, are both caused by the leakage of blood from tiny capillaries under the skin. In addition to purpura and petechiae, spontaneous bruises may occur. In extreme cases, ITP may cause bleeding into the lungs, brain, or other vital organs.

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 parents consult a pediatrician or primary care doctor after noticing their child has the typical purpuric skin rash, frequent nosebleeds, or bleeding from the digestive or urinary tract.

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 may have other autoimmune diseases such as lupus (systemic lupus erythematosus or SLE), rheumatoid arthritis, or scleroderma. Women with ITP may experience unusually heavy or lengthy menstrual periods. Risk factors for the development of chronic ITP in adults include being female, age over 10 years at onset of symptoms, bruising, and having another known autoimmune disease.

When to call the doctor

When a child bruises easily, has frequent nosebleeds, bloody stools, or develops a purplish or reddish-brown rash or tiny spots of hemorrhage, the symptoms should be reported to the pediatrician or family doctor, especially if they are noticed in the weeks following measles or chickenpox or a virus infection such as mononucleosis.