Hematologic and Neoplastic Diseases
Two weeks after a viral syndrome, a 2-year-old child develops bruising and generalized petechiae, more prominent over the legs. No hepatosplenomegaly or lymph node enlargement is noted. The examination is otherwise unremarkable. Laboratory testing shows the patient to have a hemoglobin of 12.3 g/dL, white blood cell count (WBC) of 8,000/μL, and a platelet count of 15,000/μL. Which of the following is the most likely diagnosis?
a. Von Willebrand disease (vWD)
c. Idiopathic (immune) thrombocytopenic purpura (ITP)
e. Thrombotic thrombocytopenic purpura (TTP)
The answer is c. (Hay et al, pp 859-861. Kliegman et al, pp 1714-1718. McMillan et al, pp 1731-1733. Rudolph et al, pp 1582-1583.) In children, ITP is the most common form of thrombocytopenic purpura. In most cases, a preceding viral infection can be noted. Autoantibodies to platelet membrane antigens cause increased platelet destruction by macrophages, particularly those in the spleen. No diagnostic test identifies this disease; exclusion of the other diseases listed in the question is necessary. In this disease, the platelet count is frequently less than 20,000/μL, but other laboratory tests yield essentially normal results, including the bone marrow aspiration (if done). Complications are uncommon; significant bleeding occurs in only 5% of cases and intracranial hemorrhage is even rarer. The treatment of childhood ITP is controversial. Patients with mild symptoms such as bruising and self-limited epistaxis may be observed, while patients with significant bleeding should be treated. IVIG and corticosteroids are effective in causing a rapid increase in platelet count, but controversy exists surrounding the use of prednisone before ruling out leukemia with a bone marrow aspirate. For Rh-positive patients with a working spleen, the use of anti-D immunoglobulin also results in an increase in platelet count. Platelet transfusion usually is not indicated, as anti-platelet autoantibodies will target the transfused platelets as well. Only in cases of life-threatening hemorrhage (such as an intracranial hemorrhage) is transfusion appropriate. For patients with chronic (> 1 year) ITP, a splenectomy may be necessary.
Aplastic anemia is unlikely if the other cell lines are normal. vWD might be expected to present with bleeding and not just bruising. It is unlikely that acute leukemia would present with thrombocytopenia only. TTP is rare in children.
An 11-month-old African American boy has a hematocrit of 24% on a screening laboratory done at his well-child checkup. Further testing demonstrates: hemoglobin 7.8 g/dL; hematocrit 22.9%; leukocyte count 12,200/μL with 39% neutrophils, 6% bands, 55% lymphocytes; hypochromia on smear; free erythrocyte protoporphyrin (FEP) 114 μg/dL; lead level 4 μg/dL whole blood; platelet count 175,000/μL; reticulocyte count 0.2%; sickle cell preparation negative; stool ...