A 22-month-old boy is brought to his pediatrician by his parents because he has developed several dark purple bruises on his back and spine (Figure 210-1). He has additional bruises over both legs (Figure 210-2) along with smaller bruises over his neck and cheeks. He developed these over the past 2 to 3 days, and his mother reports that 3 weeks prior to this presentation, he had an illness characterized by vomiting, nausea, and diarrhea. The pediatrician suspects immune thrombocytopenic purpura (ITP) and orders a CBC, which shows a normal white blood cell count, differential count, and hemoglobin, but a platelet count of 7,000 microL. His liver function studies, prothrombin time (PT), and partial thromboplastin time (PTT) are all normal. A diagnosis of ITP is made and the child is admitted to the hospital, where his activity is restricted and he is treated with intravenous immunoglobulin. His platelet count increases rapidly over 3 days and he is discharged home with close follow-up.

Immune thrombocytopenia purpura (ITP), formerly called idiopathic thrombocytopenic purpura, is an acquired disorder in which there is increased destruction of platelets causing thrombocytopenia (platelet count <100,000 microL). ITP may be divided into acute and chronic forms. Acute ITP is defined as having duration less than 6 months while chronic ITP is defined as lasting more than 6 months.

Idiopathic Thrombocytopenic Purpura.

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  The incidence of symptomatic disease is estimated to be 3 to 8 per 100,000 per year.^1–3

  
  
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  Acute ITP is the most common bleeding disorder in children.

  
  
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  It is seen most frequently in children between the ages of 2 and 10 years with a peak occurring between 2 and 5 years of age.²

  
  
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  It affects males more frequently among children younger than 8 years and equally among males and females beyond that age.²

  
  
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  More common in winter and spring.

  
  
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  In approximately 2/3 of cases, ITP in children occurs within 6 weeks of a recent viral illness.⁴

  
  
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  Chronic ITP is defined as persistent thrombocytopenia that persists for longer than 6 months from the initial presentation. This occurs in 10 to 20 percent of children with ITP.

  
  
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  Chronic ITP occurs more frequently in adolescents (and adults) than in young children. It affects females more than males and may be associated with underlying autoimmune disorders such as collagen-vascular diseases.

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  ITP is an immune mediated process whereby the body produces antibodies that attach to the glycoproteins expressed on platelet membranes.⁵

  
  
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  The spleen and reticuloendothelial system then destroy the antibody coated platelets.

  
  
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  There appears to be some differences between acute and chronic ITP with respect to pathophysiologic mechanisms. It is believed that acute ITP occurs when antibodies produced in response to a viral or bacterial infection cross-react with platelet antigens. On the other hand, chronic ITP may be the result of an underlying defect in immune regulation. There is also evidence of decreased thrombopoietin level in chronic ITP patients and megakaryocytes from patients with chronic ITP may demonstrate decreased growth in vitro.

  
  
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  ITP may rarely follow measles-mumps-rubella (MMR) vaccination. Although mild thrombocytopenia after such vaccination is not uncommon, the incidence of clinically significant thrombocytopenia (<50,000 microL) is between 1:30,000 and 1:40,000 vaccinations. The onset is within 6 weeks of vaccination and the majority of cases resolve within 1 month and in 93 percent of the children, the thrombocytopenia resolves within 6 months.^6,7

  
  
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  Vaccination is not associated with a relapse of ITP in children with a history of non-vaccine associated ITP but revaccination may be associated with relapse in children with vaccination associated disease.

  
  
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  ITP is felt to be unlikely after other early childhood vaccines.

The diagnosis is suggested by the finding of isolated thrombocytopenia in an otherwise healthy child. A history of a recent viral illness, especially in children under the age of 10 years, is common.

Clinical Features

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  Acute presentation of bruising, bleeding, and/or a petechial rash in an otherwise healthy child is the most common presentation.

  
  
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  Mucosal bleeding, especially in the nares and gums, may be present.

  
  
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  Physical examination reveals signs of bleeding, including petechiae, purpura and ecchymoses (Figures 210-1 to 210-4).

  
  
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  Mucosal bleeding involving the nares, gingiva, gastrointestinal, genitourinary, or vaginal tract may be present.

  
  
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  Increased menstrual flow may be present.

  
  
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  Amount of bleeding is usually related to the degree of thrombocytopenia.

  
  
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  Except for signs of cutaneous and mucosal bleeding, the child usually appears well. Lymphadenopathy, hepatomegaly and splenomegaly are not present, although the spleen tip may be palpated in a minority of cases.

  
  
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  Serious gastrointestinal or intracranial bleeding occurs in about 1 to 3 percent of patients. These are usually associated with platelet counts of less than 20,000/microL.

  
  
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  Intracranial hemorrhage is the most serious consequence of ITP and occurs in 0.1 to 1.0 percent of patients.^2,8