PMC9366100_01
PMC9366100_02
(A) Low power view (Top) of hypocellular bone marrow biopsy (~30% cellular) taken at 26 months of age (4x, H, and E stain) in the patient with MPL-mutant CAMT. Higher power view (Middle) of hypocellular marrow with myeloid and erythroid hematopoiesis and absence of megakaryocytes (10x, H, and E stain). Immunohistochemical stain for CD42b (platelet receptor for von Willebrand factor) is negative (Bottom), confirming absent megakaryocytes (10x). (B) Total, T cell, and myeloid donor chimerism through 14 months post-bone marrow transplant showing evolution to complete myeloid donor chimerism and rising donor T cell chimerism over time.
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F1
A repeat BM biopsy (Figure 1A) at this time showed evolving hypocellularity (30-40%) with absent megakaryocytes. Initial peripheral blood donor chimerism was 76% overall on Day +28 with 88% myeloid donor chimerism (Figure 1B).