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Bone Marrow The bone marrow is usually readily aspirated but dilute on smear, and the fatty biopsy specimen may be grossly pale on withdrawal; a "dry tap" instead suggests fibrosis or myelophthisis. | Chapter 102. Aplastic Anemia Myelodysplasia and Related Bone Marrow Failure Syndromes Part 7 Bone Marrow The bone marrow is usually readily aspirated but dilute on smear and the fatty biopsy specimen may be grossly pale on withdrawal a dry tap instead suggests fibrosis or myelophthisis. In severe aplasia the smear of the aspirated specimen shows only red cells residual lymphocytes and stromal cells the biopsy which should be 1 cm in length is superior for determination of cellularity and shows mainly fat under the microscope with hematopoietic cells occupying 25 of the marrow space in the most serious cases the biopsy is virtually 100 fat. The correlation between marrow cellularity and disease severity is imperfect in part because marrow cellularity declines physiologically with aging. Additionally some patients with moderate disease by blood counts will have empty iliac crest biopsies while hot spots of hematopoiesis may be seen in severe cases. If an iliac crest specimen is inadequate cells may also be obtained by aspiration from the sternum. Residual hematopoietic cells should have normal morphology except for mildly megaloblastic erythropoiesis megakaryocytes are invariably greatly reduced and usually absent. Areas adjacent to the spicule should be searched for myeloblasts. Granulomas in cellular specimens may indicate an infectious etiology of the marrow failure. Ancillary Studies Chromosome breakage studies of peripheral blood using diepoxybutane or mitomycin C should be performed on children and younger adults to exclude Fanconi s anemia. Genetic analysis applicable to the constitutional marrow failure states is available in some laboratories. Chromosome studies of bone marrow cells are often revealing in MDS and should be negative in typical aplastic anemia. Flow cytometric assays have replaced the Ham test for the diagnosis of PNH. Serologic studies may show evidence of viral infection such as Epstein-Barr virus and HIV. Posthepatitis aplastic anemia is .
