Diagnosing Leukemia: Understanding the Criteria for Acute and Chronic Forms
Leukemia is broadly categorized into two main types: acute leukemia and chronic leukemia. The latter further divides into chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML). Accurate diagnosis depends on a thorough evaluation of cellular characteristics, bone marrow composition, genetic markers, and clinical symptoms. Modern diagnostic protocols combine laboratory findings with patient history to ensure early detection and effective management.
Acute Leukemia: Rapid Onset and Aggressive Progression
Acute leukemia is characterized by the rapid accumulation of immature blood cells, known as blasts, in the bone marrow and bloodstream. A definitive diagnosis is typically made when blast cells account for 20% or more of the nucleated cells in the bone marrow. This threshold is a key benchmark used by hematologists worldwide.
Patients with acute leukemia often experience a sudden onset of symptoms, including severe fatigue, frequent infections due to low white blood cell function, easy bruising or bleeding from thrombocytopenia (low platelet count), and anemia-related weakness. Because the disease progresses quickly, prompt diagnosis and immediate treatment—usually involving chemotherapy, targeted therapy, or stem cell transplantation—are critical to improving survival rates.
Chronic Leukemia: Slower Progression with Unique Diagnostic Markers
In contrast to its acute counterpart, chronic leukemia develops gradually and may remain asymptomatic for years. However, careful monitoring and timely intervention are essential once signs of disease progression appear. There are two primary subtypes: chronic lymphocytic leukemia and chronic myeloid leukemia, each with distinct diagnostic criteria and treatment pathways.
Chronic Lymphocytic Leukemia (CLL): B-Cell Dominance and Watchful Waiting
Chronic lymphocytic leukemia primarily involves abnormal B-lymphocytes that accumulate slowly in the blood, bone marrow, and lymph nodes. In early stages, many patients do not require immediate treatment—a strategy referred to as "watchful waiting." Diagnosis is confirmed through flow cytometry, which identifies specific surface markers on B cells such as CD5, CD19, and CD23.
When symptoms like persistent low-grade fever, unexplained weight loss, night sweats, or enlarged lymph nodes emerge, treatment becomes necessary. Targeted therapies have revolutionized CLL management. BTK inhibitors—such as ibrutinib, acalabrutinib, and zanubrutinib—have shown remarkable efficacy in controlling disease progression and extending progression-free survival, with fewer side effects than traditional chemotherapy.
Chronic Myeloid Leukemia (CML): Genetic Signature and Targeted Treatment
Chronic myeloid leukemia is defined by the presence of the Philadelphia chromosome, a genetic abnormality resulting from a translocation between chromosomes 9 and 22 (t(9;22)), which produces the BCR-ABL1 fusion gene. This mutation drives the overproduction of mature and maturing granulocytes, particularly neutrophils, in the bone marrow and peripheral blood.
Diagnosis is typically confirmed via molecular testing, including fluorescence in situ hybridization (FISH) or quantitative polymerase chain reaction (qPCR) to detect BCR-ABL1 transcripts. Patients may present with splenomegaly (enlarged spleen), fatigue, or abdominal discomfort due to organ enlargement.
The advent of tyrosine kinase inhibitors (TKIs) such as imatinib, dasatinib, nilotinib, and bosutinib has transformed CML from a fatal disease into a manageable chronic condition for most patients. These drugs specifically target the abnormal protein produced by the BCR-ABL1 gene, leading to deep molecular responses.
Exciting research is now focused on achieving treatment-free remission (TFR)—a state where patients maintain undetectable disease levels even after discontinuing medication. This goal is becoming increasingly attainable for individuals who sustain long-term molecular remission under TKI therapy.