Diagnosis and Clinical Presentation
Children with ALL develop symptoms related to infiltration of blasts in the bone marrow, lymphoid system, and extramedullary sites, such as the central nervous system (CNS). Common constitutional symptoms include fever (60%), fatigue (50%), pallor (25%), and weight loss (26%). Infiltration of blast cells in the marrow cavity and periosteum often lead to bone pain (23%) and disruption of normal hematopoiesis. Thrombocytopenia with platelet counts less than 100,000 are seen in about 75% of patients. Approximately 40% of patients with childhood ALL present with hemoglobin levels less than 7 g/dL. Although leukocyte counts greater than 50,000/mm3 occur in 20% of cases, neutropenia defined as an absolute neutrophil count less than 500 is common at presentation and is associated with an increased risk of infection.[15,16] Infiltration of the lymphoid system may cause lymphadenopathy and hepatosplenomegaly. CNS involvement is found in less than 5% of children at presentation. When present, the signs and symptoms include headache, vomiting, papilledema, and sixth-nerve palsy.[17,18,19]
Although peripheral blasts with anemia and thrombocytopenia are strongly suggestive of ALL, the definitive diagnosis of ALL is based on the bone marrow aspiration or biopsy demonstrating more than 25% lymphoblasts. In patients with large leukemia cell burden, serum chemistries may reveal signs of tumor lysis, including hyperkalemia, hypocalcemia, hyperphosphatemia, and lactic acidosis. Serum uric acid may be elevated due to increased cell turnover. Tumor lysis can be a metabolic emergency at the time of presentation and may be exacerbated by initiation of therapy.
Once the diagnosis of ALL is made, cytogenetic analysis, immunophenotyping by flow cytometry, and immunohistochemical staining are performed to further characterize ALL subtype and guide therapy. A lumbar puncture and cerebrospinal fluid examination are also performed to determine the presence of occult CNS involvement.
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Cite this: Topics in Pediatric Leukemia -- Acute Lymphoblastic Leukemia - Medscape - Feb 28, 2005.