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.
Purpuric and ecchymotic lesion over the back, and petechial lesions on the face of a child with immune thrombocytopenic purpura. (Used with permission from Margaret C Thompson, MD, PhD.)
A. Large purpuric lesions on the legs of the child in Figure 210-1. B. Close-up of an ecchymotic lesion on the same child. (Used with permission from Margaret C Thompson, MD, PhD.)
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.
The incidence of symptomatic disease is estimated to be 3 to 8 per 100,000 per year.1–3
Acute ITP is the most common bleeding disorder in children.
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
It affects males more frequently among children younger than 8 years and equally among males and females beyond that age.2
More common in winter and spring.
In approximately 2/3 of cases, ITP in children occurs within 6 weeks of a recent viral illness.4
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.
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.
Etiology and Pathophysiology