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Constitutional symptoms (fever and weight loss), petechial rash, and blasts on peripheral blood smear in a child are very concerning for acute lymphoblastic leukemia (ALL). Stridor suggests a mediastinal mass which is found in T-cell ALL. Pre-T-cell markers include CD2 - CD8.Peak incidence of ALL is in children aged 2-5 years. B-cell precursors form 70-80% of ALL cases and have a more favorable prognosis than the less common pre-T-cell ALL cases. Pre-T-cell ALL results in a mass in the anterior mediastinum due to thymic enlargement, which may compress both the trachea and the esophagus, which are posterior to it, and cause cough, dysphagia, or dyspnea. Superior vena cava syndrome may also result from compression of the mediastinal vessels by the enlarging mass. Young et al. provide an overview of diagnosis of common childhood malignancies for the primary care physician. More than half of cancer cases in children are leukemias, lymphomas, and CNS tumors. They note that leukemias should be suspected if the child has bleeding, bone pain, or lymphadenopathy. Attarbaschi et al. conducted a retrospective study of 116 Austrian patients to examine whether responsiveness of mediastinal mass to treatment predicted overall treatment outcome. 70/116 patients presented with initial mediastinal mass. In patients whose mass had incompletely responded to therapy by either day 35 or day 70, outcomes were no worse when compared to responders. They suggest that lack of mass response to therapy should not be used as a sign that overall treatment is failing. However, validation of this finding in prospective trials is indicated.Figure A shows a child with petechial rash as would be seen in ALL.Figure V shows inspiratory stridor which is caused in this child by compression of the trachea due to the mediastinal mass.Illustration A compares CD markers between B and T cells throughout their maturation.Incorrect Answers:Answer 1: CD1 is expressed on mature antigen presenting cells, not pre-T-cells, and functions in aiding T-cell recognition of lipid antigens.Answers 3-5: Pre-B-cell ALL would be expected to express CD10, CD19, CD20.
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