3.2 Acute Myeloid Leukemia and Related Myeloid Disease

Acute myeloid leukemia (AML) is less common than ALL in children, but it is not a milder disease. AML biology is myeloid rather than lymphoid, treatment produces deeper and more prolonged myelosuppression, invasive fungal infection is a real induction threat, and hematopoietic stem cell transplant (HSCT) is used more often than in ALL for high-risk or relapsed disease. CPHON questions often hinge on three special entities—acute promyelocytic leukemia (APL), myeloid disease in Down syndrome, and chloromas—plus the emergency of hyperleukocytosis with leukostasis.

How AML differs from ALL at the bedside

Children with AML may present with fever, pallor, bleeding, gingival infiltration, bone pain, or a soft-tissue mass. Circulating myeloid blasts, anemia, and thrombocytopenia are common. The white-cell count may be extremely high. Compared with ALL, families should hear a different intensity message: fewer months of total therapy than ALL's 2- to 3-year backbone, but far more profound aplasia per cycle and a higher early-death risk from infection, bleeding, and leukostasis.

Chloromas (myeloid sarcomas) are extramedullary collections of myeloid blasts. They can appear in skin, orbit, gingiva, bone, or the CNS. A greenish hue is historically described because of myeloperoxidase, but many chloromas are not green. An orbital or facial mass in a child with cytopenias is not just cellulitis until myeloid disease is excluded.

Classification: FAB versus WHO, without memorizing a museum

Older teaching used the French-American-British (FAB) morphologic types M0 through M7. Contemporary diagnosis uses World Health Organization (WHO) categories that integrate morphology, immunophenotype, cytogenetics, and molecular genetics. Nurses are not scored on reciting every FAB subtype, but you should recognize why lineage and genetics change treatment: core-binding-factor AML, KMT2A-rearranged AML, and APL are not interchangeable. Monoblastic and myelomonocytic disease (historically FAB M4/M5) is the group most associated with gum infiltration, chloromas, and leukostasis.

APL: a nursing emergency

APL is defined by t(15;17) creating the PML-RARA fusion. The clinical crisis is coagulopathy—disseminated intravascular coagulation (DIC) and hyperfibrinolysis—not simply a high blast count. A teenager with bruising, gingival oozing, a rapidly falling fibrinogen, and a new APL diagnosis can bleed into the brain before the first conventional chemotherapy dose. Priority is urgent initiation of differentiation therapy with tretinoin (all-trans retinoic acid) and, on current protocols, arsenic trioxide, plus aggressive blood-product support for DIC. Do not wait for a perfectly complete genetic report if the morphology and coagulation picture already scream APL; start differentiation therapy per protocol while confirmation is pending.

Differentiation syndrome (formerly called retinoic-acid syndrome) is the treatment-related counterpart: fever, weight gain, edema, hypotension, respiratory distress, and pleural or pericardial effusions as promyelocytes mature. Hold differentiating agents per protocol and give dexamethasone when the syndrome is diagnosed. Do not teach APL as ALL with a different name. An asparaginase-vincristine induction map is the wrong map and delays the one intervention that stops the coagulopathy.

Down syndrome: TAM and ML-DS

Neonates with Down syndrome can develop transient abnormal myelopoiesis (TAM), also called transient myeloproliferative disorder. Circulating blasts, often megakaryoblastic, and GATA1-mutation biology are characteristic. Many cases regress spontaneously, but TAM can cause life-threatening liver failure, respiratory compromise, or hydrops and can later evolve into myeloid leukemia of Down syndrome (ML-DS). ML-DS typically appears in the first 4 years of life, often around 1 to 2 years of age.

ML-DS is usually treated with reduced-intensity AML-style therapy compared with non–Down syndrome AML, because these children are both more chemosensitive and more vulnerable to toxic death. Nursing takeaway: not every neonate with Down syndrome and blasts goes straight to transplant, and protocol observation is not neglect when it is paired with close laboratory and organ surveillance. Conversely, do not dismiss progressive cytopenias at age 18 months in a child with a TAM history as ordinary viral marrow suppression.

Induction backbone, infection, and transplant

Pediatric AML induction is built on cytarabine plus an anthracycline (often daunorubicin or mitoxantrone; protocol-specific), with additional agents such as etoposide on some regimens (for example, ADE-style blocks). Gemtuzumab ozogamicin appears on selected protocols. Cycles produce prolonged severe neutropenia. Invasive fungal infection—Candida and molds such as Aspergillus—is a major cause of morbidity. Many children receive mold-active prophylaxis during intensive AML therapy; fever that persists despite antibacterial drugs triggers imaging and antifungal escalation. Mucositis, typhlitis, central-line infection, and septic shock are day-to-day nursing threats.

Because residual disease and genetics drive outcome, HSCT in first remission is used more often in high-risk AML than in standard-risk ALL. Relapsed AML is also a common transplant indication. Start transplant education earlier than you would for standard-risk B-ALL. Nursing roles include infection isolation teaching, central-line care, nutritional support through mucositis, and early recognition of abdominal pain that may be typhlitis.

Hyperleukocytosis and leukostasis

Hyperleukocytosis with true leukostasis—sludging of blasts in the microcirculation—is more classic in AML than in ALL, especially monoblastic subtypes. The child with a WBC well above 100,000/µL who develops dyspnea, hypoxia, visual change, headache, or confusion is in a medical emergency. Management is protocol-based cytoreduction, careful transfusion (avoid overtransfusing red cells, which raise viscosity), hydration, and prevention of TLS as blasts fall. Leukapheresis is used selectively, not automatically, and never replaces starting disease-directed therapy.

Keep the comparison honest: ALL still causes TLS, infection, and occasional hyperleukocytosis. What AML uniquely demands on CPHON is the DIC/APL script, the Down syndrome myeloid script, chloromas, fungal risk during prolonged aplasia, and leukostasis in monoblastic disease.