Pediatric Case Studies – Case 1 – Immune thrombocytopenic purpura (ITP)

A previously healthy 3-year-old boy presents with sudden onset of rash. His mother says he had been playing when she noticed small red spots and a large purple area on his skin. He has had no fever, upper respiratory tract infection (URI) symptoms, weight loss, bone pain, or diarrhea, and he is not taking medications. Three weeks previously, he had a mild illness that self-resolved after 48 hours. He is playful on examination, but he has multiple petechiae and purpuric lesions on his upper and lower extremities and on his trunk. He has neither adenopathy nor splenomegaly. His white blood cell (WBC) count is 8500/mm3, hemoglobin level is 14 mg/dL, and his platelet count is 20,000/mm3.

• What is the most likely diagnosis?
• What is the next step in management?

Summary

A healthy 3-year-old develops thrombocytopenia, petechiae, and purpuric lesions. He is well appearing but recently had a febrile illness. His WBC count and hemoglobin levels are normal.

Most likely diagnosis

Immune thrombocytopenic purpura (ITP).

Next step in management: Evaluation of his peripheral blood smear.

ANALYSIS

Objectives

1. Know the most common causes of childhood thrombocytopenia.

2. Understand the natural history of ITP.

Considerations

This 3-year-old has purpuric lesions and petechiae resulting from thrombocytopenia. He lacks the systemic signs of illness expected with disseminated intravascular coagulation or hemolytic-uremic syndrome (HUS).

Because his hemoglobin level and WBC count are normal, bone marrow infiltration is less likely the cause of his thrombocytopenia. A peripheral blood smear is examined to identify immature WBCs and red cell morphology.

Children with ITP have normal peripheral blood smears without evidence of leukemic or microangiopathic processes. This child has a platelet count of 20,000/mm3 and lacks evidence of active bleeding; the next step is close observation.

APPROACH TO: Thrombocytopenia

DEFINITIONS

HEMOLYTIC-UREMIC SYNDROME (HUS): A syndrome of nephropathy, thrombocytopenia, and microangiopathic hemolytic anemia. It is associated with Escherichia coli 0157:H7, Shigella, and Salmonella. A prodrome of bloody diarrhea is common.

HENOCH-SCHÖNLEIN PURPURA (HSP): A syndrome of small-vessel vasculitis in young children. The syndrome may have dermatologic (petechial/purpuric rash), renal (nephritis), gastrointestinal (abdominal pain, gastrointestinal bleeding, intussception), and joint involvement (arthritis).

IMMUNE THROMBOCYTOPENIC PURPURA (ITP): A condition of increased platelet destruction by circulating antiplatelet antibodies, most frequently antiglycoprotein IIb/IIIa.

CLINICAL APPROACH

Acute Immune thrombocytopenic purpura is the most common cause of thrombocytopenia in a well child usually aged 2 to 10 years.

The evidence suggests an immunologic etiology triggered by a preceding viral illness, but the specific pathophysiologic mechanism is unknown. Acute Immune thrombocytopenic purpura occurs with an equal gender distribution.

Young children usually present with acute onset of petechiae and purpura and a history of a viral illness 1 to 4 weeks previously. Bleeding from the gingivae and other mucous membranes may occur. Examination findings include petechiae and purpura, especially in trauma areas. If significant lymphadenopathy or organomegaly is found, other causes for thrombocytopenia are considered.

Laboratory findings include thrombocytopenia, which can be severe (<20,000/mm3), but the platelet size is normal or increased. The WBC count and hemoglobin level are normal (unless excessive bleeding has occurred).

Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are normal. The peripheral blood smear may reveal eosinophilia or atypical lymphocytes; immature WBCs and abnormal red cell morphology are absent.

Generally, bone marrow aspiration is unnecessary. If the peripheral blood smear is concerning, the WBC count is abnormal, or adenopathy or organomegaly is present, bone marrow evaluation aids in proper diagnosis, demonstrating an increased number of megakaryocytes in ITP. Within a month of presentation, more than half of untreated children have complete resolution of their thrombocytopenia and up to another 30% have resolution by 6 months.

Persistence beyond 6 months is considered chronic Immune thrombocytopenic purpura.

The most serious ITP complication, intracranial hemorrhage, occurs in less than 1% of affected children.

Patients with severe thrombocytopenia (<20,000/mm3), extensive mucosal bleeding, severe complications (eg, massive gastrointestinal bleeds), or without a protective environment may require medical intervention.

Treatment to decrease platelet destruction includes intravenous immunoglobulin for 1 to 2 days, intravenous anti-D therapy, or a 2-to 3-week course of systemic corticosteroids. Platelet transfusion is reserved for life-threatening bleeding. Splenectomy may be considered in children with serious complications not responding to other therapies. After splenectomy, pneumococcal vaccine and penicillin prophylaxis are required because of risk for sepsis.

From 10% to 20% of ITP patients have chronic thrombocytopenia lasting for more than 6 months, occurring more commonly in older children and in females; it may be part of other autoimmune disease or may occur with infection such as human immunodeficiency virus (HIV) or Epstein-Barr virus (EBV).

The ITP treatment options listed above are available for chronic ITP patients; the goal remains prevention of serious thrombocytopenia complications.

Many pharmacologic agents may cause immune-mediated thrombocytopenia, including penicillins, trimethoprim-sulfamethoxazole, digoxin, quinine, quinidine, cimetidine, benzodiazepine, and heparin. The measles, mumps, and rubella (MMR) vaccine is associated with thrombocytopenia and is used cautiously in ITP patients.

Pediatric Case Studies – Case 1 – Immune thrombocytopenic purpura (ITP)

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