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Bone Marrow Transplantation: Indications, Donor Matching, and Transplant Types

What Is Bone Marrow Transplantation?

Hematopoietic stem cell transplantation (HSCT) replaces diseased or damaged bone marrow with healthy stem cells. It is curative for many hematologic malignancies, bone marrow failure syndromes, immune deficiencies, and metabolic disorders.

Transplant Types

  • Autologous: Patient’s own stem cells (harvested pre-chemotherapy). Used for multiple myeloma, lymphoma, some solid tumors. No graft-versus-host disease (GVHD) risk.
  • Allogeneic: Stem cells from a donor. Curative potential via graft-versus-leukemia/tumor effect. Requires HLA matching.
    • Matched related donor (MRD): Sibling (25% chance per sibling).
    • Matched unrelated donor (MUD): Via registries (e.g., NMDP/Be The Match).
    • Haploidentical: Half-matched family member (parent, child, half-sibling) with post-transplant cyclophosphamide to reduce GVHD.
    • Umbilical cord blood: Lower cell dose, less stringent HLA matching, slower engraftment.

HLA Matching: The Critical Factor

Human leukocyte antigen (HLA) genes on chromosome 6 encode proteins that present peptides to T cells. High-resolution matching at HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1 (10/10 or 12/12 alleles) minimizes rejection and GVHD. Mismatches increase risks but may be acceptable with haploidentical protocols.

Donor Selection Process

  1. HLA typing of patient and potential related donors.
  2. If no MRD, search unrelated donor registries and cord blood banks.
  3. Confirmatory typing, infectious disease screening, and donor health assessment.
  4. Stem cell source: Peripheral blood stem cells (PBSC, most common), bone marrow harvest, or cord blood.

Key Complications

  • GVHD (acute/chronic) – major cause of morbidity/mortality in allogeneic HSCT.
  • Infections (bacterial, viral, fungal) during neutropenia and immune reconstitution.
  • Veno-occlusive disease (VOD/SOS), hemorrhagic cystitis, organ toxicity from conditioning.
  • Relapse of underlying disease.

HSCT requires a multidisciplinary team and specialized center. Outcomes have improved dramatically with better HLA typing, reduced-intensity conditioning, and supportive care.

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