Studies of fetal hemoglobin and bone marrow ultrastructure were performed on a patient with a recently described syndrome consisting of lymphosarcoma, short stature, defective cellular Immunity, hypogammaglobulinemia, and mosaicism for a marker chromosome. Abnormalities of the erythroid cells, including multinucleated erythroblasts, nuclear bodies, megaloblasts, and frayed cytoplasm, were seen ...