Acute myeloid leukemia

Acute lymphoblastic leukemia is a clonal proliferation of lymphoid precursor blasts that replace the bone marrow, the most common cancer in children, diagnosed when TdT-positive lymphoblasts make up 20% or more of the marrow and classified by flow cytometry immunophenotype and cytogenetics. Treatment is multi-phase chemotherapy (induction, consolidation, CNS prophylaxis, maintenance for up to 2 years), with a tyrosine kinase inhibitor added for Philadelphia-chromosome-positive disease and aggressive tumor lysis prophylaxis at the start of therapy.

Chronic myeloid leukemia is a myeloproliferative neoplasm driven by the Philadelphia chromosome t(9;22), which produces the constitutively active BCR-ABL1 tyrosine kinase and marked, left-shifted granulocytosis with a low leukocyte alkaline phosphatase score. Diagnosis is confirmed by cytogenetics or molecular testing for BCR-ABL1, and a BCR-ABL tyrosine kinase inhibitor such as imatinib is first-line, continued indefinitely with molecular-response monitoring, reserving allogeneic transplant for TKI failure or blast crisis.

Myelodysplastic syndromes are clonal stem cell disorders producing ineffective hematopoiesis: a dysplastic, usually hypercellular bone marrow with peripheral cytopenias and a variable risk of transformation to acute myeloid leukemia. Diagnosis requires bone marrow biopsy showing dysplasia after excluding reversible mimics, risk is stratified with the IPSS-R, and treatment ranges from supportive transfusions and lenalidomide in lower-risk disease to hypomethylating agents and allogeneic transplant, the only cure, in higher-risk disease.

Disseminated intravascular coagulation is a secondary, systemic activation of coagulation and fibrinolysis, most often from sepsis, that simultaneously consumes platelets and clotting factors, causing microvascular thrombosis and bleeding. Diagnosis rests on a laboratory constellation, thrombocytopenia, prolonged PT and aPTT, low fibrinogen, and elevated D-dimer, in a predisposing clinical setting, and management centers on treating the underlying trigger while replacing blood components only for active or high-risk bleeding.

Tumor lysis syndrome is a metabolic oncologic emergency in which massive tumor cell breakdown, spontaneous or chemotherapy-induced, releases potassium, phosphate, and nucleic acids into the blood, producing hyperuricemia, hyperkalemia, hyperphosphatemia, and secondary hypocalcemia that can precipitate acute kidney injury, arrhythmia, seizure, and death. Risk-stratified prophylaxis with hydration plus allopurinol or rasburicase before chemotherapy, and aggressive correction of electrolytes with renal replacement therapy when needed, are the cornerstones of management.

Neutropenic fever is an oncologic emergency defined as a single oral temperature of 38.3 C or higher, or 38.0 C sustained for 1 hour, with an ANC of 500/microL or lower, most often during the chemotherapy nadir. Management is empiric antipseudomonal beta-lactam therapy within 60 minutes, with vancomycin, antifungal therapy, and growth factors added only for specific indications.

Aplastic anemia is an acquired or inherited hematopoietic stem cell disorder that produces pancytopenia with a hypocellular, fatty bone marrow and no dysplasia, blasts, or fibrosis. Diagnosis rests on marrow biopsy showing less than 25% cellularity with severity graded by the Camitta criteria, and treatment is allogeneic stem cell transplantation for young fit patients with a matched donor or antithymocyte globulin plus cyclosporine and eltrombopag for everyone else.

Graft-versus-host disease is a complication of allogeneic hematopoietic stem cell transplantation in which donor T cells attack recipient tissues, classically the skin, liver, and gut in the acute form and multi-organ fibrosis in the chronic form. Diagnosis is clinical, supported by biopsy, and management is prophylaxis with a calcineurin inhibitor plus methotrexate and treatment with corticosteroids, escalating to agents such as ruxolitinib for steroid-refractory disease.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.