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A 9-mon th-old male patien t is referred by his pediatrician due to an abnormal blood count. Leu kocyte count is 7 , 300/f..Ll. hemoglobin is 7_/..j g/dl with MCV 1 09 fl. reticu-locytes is 1 . 0%, and platelet count is 58 1 .000/ f..Ll. The physical examination reveals no abnormal fi ndi ngs . The peripheral blood smear shows mild macrocytosis but is other-wise unremarkable. The i mage below shows the bone marrow aspirate specimen.
What is the pathophysiologic defect in DBA?
- Defective telomerase enzyme
- Defective ribosome synthesis
- Mutation in colony stimulating factor gene
- Sensitivity to apoptosis due to defective surface receptor proteins
Medicine
B. DBA is caused by failure of hematopoiesis due to ineffective ribosomal proteins. Multi-ple genes have been implicated in DBA, including RPS 19 in 25% of patients. In one study of219 patients, 129 distinct mutations were found. Haploinsufficiency for ribosomal protein genes may cause activa-tion of p53 in erythroid progenitor cells in DBA (ISO Hum Mutat. 201 0;3 1 (12):1269). (Blood. 201 1;11 7:2567-2576).
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