Complications of Transplantation

Transplant Rejection - Attack of the Clones

• Recipient's immune system attacks donor alloantigens (MHC/HLA).
• Types & Timing (📌 Mnemonic: Hot Apple Crumble):

  • Hyperacute Rejection:

    • Minutes to hours.
    • Cause: Pre-formed anti-donor antibodies (e.g., ABO, anti-HLA Class I).
    • Mechanism: Type II Hypersensitivity. Results in complement activation, endothelial damage, thrombosis, graft necrosis.

  • Acute Rejection:

    • Days to weeks (usually <6 months); most common type.
    • Cellular: CD8+ T-cells (cytotoxic) directly damage graft; CD4+ T-cells (helper) mediate inflammation. Type IV HSR.
    • Humoral: Anti-donor antibodies (de novo or anamnestic) target graft vasculature. Type II HSR.

  • Chronic Rejection:

    • Months to years. Often irreversible, leading to progressive graft failure.
    • Mechanism: Complex; involves cellular and humoral immunity, cytokines, growth factors.
    • Pathology: Vascular changes (graft arteriosclerosis), interstitial fibrosis, parenchymal atrophy.
• Diagnosis: Graft biopsy is the gold standard.
• Prevention: HLA matching, immunosuppressive drugs.

⭐ Acute cellular rejection, primarily mediated by T-lymphocytes, is the most common form of rejection and is often reversible with increased immunosuppression.

Post-Transplant Infections - Bugs on Board

Post-transplant infections impact outcomes. Timing reveals likely pathogens. Immunosuppression level is key.

• Common Pathogens & Concerns:
  • CMV: Pneumonitis, GI disease, hepatitis. Prophylaxis/pre-emptive therapy common.
  • PJP: Interstitial pneumonia. TMP-SMX prophylaxis.
  • Aspergillus: Invasive pulmonary disease, high mortality.
  • BK Virus: Polyomavirus nephropathy in renal transplants.
• Key Prophylaxis Durations:
  • PJP: TMP-SMX for 6-12 months.
  • CMV: Valganciclovir/Ganciclovir for high-risk (D+/R-), typically 3-6 months.
  • Fungal (Candida): Fluconazole for early post-op period.
  • HSV/VZV: Acyclovir/Valacyclovir if seropositive.

⭐ CMV is the most common opportunistic infection in Solid Organ Transplant (SOT) recipients, typically occurring 1-6 months post-transplant, causing fever, leukopenia, or organ-specific disease.

Drug Side Effects & PTLD - Pills & Perils

• Calcineurin Inhibitors (CNIs): Nephrotoxicity, neurotoxicity, HTN, hyperglycemia.
  • Cyclosporine: 📌 "Cyclo Spor Hirsute Gums" (Hirsutism, Gingival hyperplasia).
  • Tacrolimus: Alopecia, ↑diabetes risk.
• Antiproliferatives:
  • Mycophenolate (MMF): GI upset (diarrhea), leukopenia.
  • Azathioprine: Myelosuppression, pancreatitis.
• mTOR Inhibitors (Sirolimus, Everolimus):
  • Hyperlipidemia, impaired wound healing, mouth ulcers, pneumonitis.
• Corticosteroids:
  • Cushingoid features, hyperglycemia, osteoporosis, ↑infection risk.
• PTLD (Post-Transplant Lymphoproliferative Disorder):
  • EBV-driven lymphoma; risk ↑ with immunosuppression intensity.
  • Sx: Fever, lymphadenopathy.
  • Rx: Reduce immunosuppression, Rituximab.

  ⭐ PTLD is most commonly associated with Epstein-Barr Virus (EBV) infection in transplant recipients.

GVHD & Other Complications - Graft's Grudge

• Graft-versus-Host Disease (GVHD): Donor T-cells attack recipient tissues. 📌 Targets: Skin, Liver, Gut.
  • Acute GVHD: Develops <100 days. Affects skin (maculopapular rash), liver (↑bilirubin, ↑LFTs), GIT (diarrhea, pain).
  • Chronic GVHD: Develops >100 days. Autoimmune-like; multi-organ (skin, mouth, eyes, joints, lungs).
  • Prophylaxis/Treatment: Immunosuppressants (CNIs, methotrexate), steroids.
• Surgical Complications:
  • Vascular: Arterial/venous thrombosis, stenosis.
  • Organ-specific: Biliary strictures/leaks (liver); lymphocele, urinoma (kidney).
  • General: Wound infection, dehiscence.
• Long-term Sequelae:
  • Malignancy: PTLD (EBV-associated), skin cancers (SCC > BCC), Kaposi sarcoma.
  • Cardiovascular disease (accelerated).
  • Nephrotoxicity (CNIs).
  • Opportunistic infections.

⭐ Post-Transplant Lymphoproliferative Disorder (PTLD) is a significant EBV-related malignancy risk, especially in the first year.

High‑Yield Points - ⚡ Biggest Takeaways

• Hyperacute rejection is antibody-mediated (Type II hypersensitivity), occurring minutes to hours post-transplant.
• Acute rejection, typically T-cell mediated (Type IV), occurs days to weeks later; it's the most common type.
• Chronic rejection involves fibrosis and scarring, leading to graft loss over months to years.
• Opportunistic infections like CMV, PJP, and BK virus are significant post-transplant risks.
• Increased risk of malignancies, especially PTLD (EBV-related) and skin cancers.
• Calcineurin inhibitor toxicity (e.g., nephrotoxicity, neurotoxicity) is a major long-term concern.
• Graft-versus-host disease (GVHD) is a critical complication, especially in bone marrow transplants but can occur in solid organs too.