Acute leukemia = rapid clonal expansion of immature hematopoietic cells (blasts) in the bone marrow, spilling into blood. AML (acute myeloid): median age 68, most common adult acute leukemia. ALL (acute lymphoblastic): bimodal -peak in children 2-5y + second peak > 60y. Diagnosis: โฅ 20% blasts in marrow or blood (WHO). Exception: AML with recurrent genetic abnormalities (e.g. t(8;21), inv(16)) can be diagnosed at any blast %. APL (acute promyelocytic leukemia, M3): medical emergency -presents with severe DIC. Treat with ATRA immediately on suspicion, before confirmation. The intern's role: you will not choose chemo regimens -you WILL manage TLS prevention, febrile neutropenia, DIC, transfusion, electrolytes, and pain.
Patient: 32F with 10 days of fatigue, bruising, and epistaxis. WBC 3.2K with 45% blasts, Hgb 7.1, platelets 18K. PT 19, fibrinogen 82. Smear: bilobed blasts with heavy granulation and Auer rods.
Key findings: APL [t(15;17) PML-RARA] with DIC, the hematologic emergency. APL is the most curable leukemia but the most dangerous at presentation due to DIC-related hemorrhage.
Management:
Teaching point: APL is a clinical diagnosis, start ATRA on morphologic suspicion alone (Auer rods + DIC). Waiting for FISH costs lives. ATO+ATRA cures > 95% of low-risk APL without traditional chemotherapy.
Patient: 65M with 1 week of confusion and dyspnea. WBC 142K with 88% blasts, Hgb 8.2, platelets 34K. SpOโ 88% on room air. CXR: bilateral interstitial infiltrates. CT head: no bleed.
Key findings: Leukostasis, WBC > 100K with symptomatic microvascular plugging (pulmonary: hypoxia; CNS: confusion). AML blasts are large and sticky, leukostasis occurs at lower WBC than ALL.
Management:
Teaching point: Leukostasis is a clinical diagnosis, there is no specific WBC threshold. Do not wait for confirmatory tests. The immediate goal is cytoreduction, not diagnosis. Avoid pRBC transfusion until WBC is lowered.
Patient: 22M with 3 weeks of fatigue, bone pain, and fever. WBC 48K with 72% lymphoblasts, Hgb 9.4, platelets 28K. Mediastinal mass on CXR. Flow cytometry: TdT+, CD10+, CD19+, CD22+.
Key findings: B-cell ALL. Young adult with mediastinal mass (T-cell features possible). Must check for Philadelphia chromosome [t(9;22) BCR-ABL], present in 25% of adult ALL and changes therapy entirely.
Management:
Teaching point: Always check for Philadelphia chromosome in adult ALL, it's present in 25% of cases and is the single most important prognostic and therapeutic marker. Ph+ ALL gets TKI + chemo, not chemo alone.
Ms. Chen is a 58-year-old woman presenting with 2 weeks of fatigue, easy bruising, and gum bleeding. Exam: pallor, petechiae, gingival hyperplasia. Labs: WBC 68K with 78% blasts, Hgb 6.8, platelets 12K, LDH 1200, uric acid 9.2. Smear: large blasts with Auer rods. PT 18, fibrinogen 95.