Allogeneic Stem Cell Transplant: Process, Risks, and Indications

Allogeneic transplant uses healthy stem cells from a donor (related or unrelated) to replace diseased marrow. Key steps:

1. HLA Matching: Donor-recipient compatibility at human leukocyte antigen loci reduces graft-versus-host disease (GVHD) risk.
2. Donor Selection: Sibling (25% match chance), matched unrelated donor (registry), or haploidentical (half-matched family).
3. Conditioning: High-dose chemo ± radiation to eradicate disease and immunosuppress recipient.
4. Stem Cell Collection: Peripheral blood apheresis (most common) or bone marrow harvest.
5. Infusion: Cells given IV; migrate to marrow and engraft (2–4 weeks).
6. Supportive Care: Infection prophylaxis, transfusions, GVHD prevention (calcineurin inhibitors, methotrexate).

Indications

Leukemia, lymphoma, myeloma, aplastic anemia, hemoglobinopathies, immune deficiencies.

Major Complication

GVHD: Donor T-cells attack host tissues (skin, liver, gut). Acute (<100 days) or chronic. Managed with immunosuppression.