(a) Normal bone marrow biopsy demonstrating a predominance of erythroid precursors (note cells with round, dark nuclei). This image was originally published in ASH Image Bank. Peter Maslak. Normal adult bone marrow. ASH Image Bank. 2010; Trephine Biopsy-2. ©The American Society of Hematology. (b) Bone marrow biopsy taken from the patient, demonstrating marked reduction in erythroid precursors.