What symptom commonly arises several weeks after bone marrow transfusion?

Cytopenia is a reduction in the number of blood cells, which can indeed occur several weeks after a bone marrow transplant. The process of engraftment, where the transplanted hematopoietic cells begin to produce new blood cells, typically takes a few weeks. During this period, it is not uncommon for patients to experience a drop in blood cell counts, leading to various forms of cytopenia, including anemia (low red blood cells), thrombocytopenia (low platelets), and leukopenia (low white blood cells).

Infection can occur due to immunosuppression, but it typically presents earlier, during the immediate post-transplant period as the immune system is still recovering. While headaches may occur for various reasons during the post-operative phase, they are not specifically linked to bone marrow transplantation in the context of a common delayed symptom. Gastrointestinal bleeding could be a concern but is not as directly associated with the timing and process of bone marrow engraftment as cytopenia. Therefore, cytopenia stands out as the most characteristic symptom to expect several weeks after a bone marrow transfusion.