Complications associated with allogeneic hematopoietic cell transplantation in children

1

Why is it important to understand complications after allogeneic hematopoietic cell transplantation?

Allogeneic hematopoietic cell transplantation (AlloHCT) is a lengthy and complex process. The majority of the patients sustain complications after AlloHCT. These complications can have a significant impact on survival, quality of life, cost, and healthcare utilization. Hence, it is crucial to understand the landscape of complications after alloHCT.

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How do we classify complications after AlloHCT?

Complications after alloHCT can be divided into early complications (0–100 days), intermediate complications (101–180 days), late complications (6–24 months), and very late complications (> 24 months).

• A.

  Early complications are predominantly related to:

  • a.

    Conditioning regimens (i.e., mucositis, infections, kidney, liver, and lung injury) Immunological responses (i.e., engraftment syndrome, acute graft-versus-host disease [aGVHD], idiopathic pneumonia syndrome, and graft rejection) and/or

  • b.

    Polypharmacy (i.e., posterior reversible encephalopathy syndrome from calcineurin inhibitors, renal insufficiency because of antibiotics and calcineurin inhibitors, liver injury because of antibiotics, total parenteral nutrition, myelosuppression because of mycophenolate mofetil and antiviral medications).

• B.

  Intermediate complications are usually because of the presence of aGVHD and chronic GVHD (cGVHD) and because of the immunosuppressive therapies used to control these complications. This often predisposes patients to bacterial, viral, and fungal infections.

• C.

  Late complications often are a byproduct of cGVHD therapy. The backbone of cGVHD therapy includes steroids, which can predispose patients to osteopenia and avascular necrosis of the bones, short stature, chronic hypertension, and adrenal suppression.

• D.

  Very late complications are not infrequent and many of those complications are related to conditioning regimens, including alkylating agents and total body irradiation. These complications include gonadal failure resulting in early menopause, infertility, growth retardation, thyroid dysfunction, cataracts, and second malignancies.

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What are the most common infections after transplant and their time course?

After alloHCT, children are at risk for several opportunistic infections. The majority of the infections among transplant patients are derived from the host gastrointestinal (GI) tract, skin, and/or respiratory system. Because of a weakened host innate immune system, gut dysbiosis, central lines, and other catheters, patients are at risk for bacterial, fungal, and viral infections. Additionally, once discharged after alloHCT, patients are not only at risk of opportunistic infections but also community-acquired infections such as, but not limited to, influenza, respiratory syncytial virus, and parainfluenza. Patterns of infection are time dependent as summarized in Figure 51.1 .

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