Leukemia, Acute
Beginning as a malignant proliferation of white blood cell (WBC) precursors, or blasts, in bone marrow or lymph tissue, acute leukemia results in an accumulation of these cells in peripheral blood, bone marrow, and body tissues. (See Forms of acute leukemia.)
The disease is more common in males than in females, in whites (especially those of Jewish ancestry), in children between ages 2 and 5 (80% of all leukemias in this age-group are acute lymphoblastic ([lymphocytic] leukemia [ALL]), and in those who live in urban and industrialized areas.
Pediatric pointerAmong children, acute leukemia is the most common form of cancer.
Untreated, acute leukemia is invariably fatal, usually because of complications resulting from leukemic cell infiltration of bone marrow or vital organs. With treatment, the prognosis varies.
In ALL, treatment induces remissions in 90% of children (average survival time: 5 years) and in 65% of adults (average survival time: 1 to 2 years). Children between ages 2 and 8 have the best survival rate—about 50%—with intensive therapy.
In acute myeloblastic (myelogenous) leukemia (AML), the average survival time is only 1 year after diagnosis, even with aggressive treatment. Remissions lasting 2 to 10 months occur in 50% of children; adults survive only about 1 year after diagnosis of AML, even if they receive treatment.
Causes
The exact cause of acute leukemia is unknown; however, radiation (especially prolonged exposure), certain chemicals and drugs, viruses, genetic abnormalities, and chronic exposure to benzene are likely contributing factors.
Forms of acute leukemia
The most common forms of acute leukemia include:
acute lymphoblastic (lymphocytic) leukemia, characterized by abnormal growth of lymphocyte precursors (lymphoblasts)
acute myeloblastic (myelogenous) leukemia, which causes rapid accumulation of myeloid precursors (myeloblasts)
acute monoblastic (monocytic) leukemia, or Schilling’s type, which results in a marked increase in monocyte precursors (monoblasts).
Other variants are acute myelomonocytic leukemia and acute erythroleukemia.
In children, Down syndrome, ataxia, and telangiectasia may increase the risk, as may such congenital disorders as albinism and congenital immunodeficiency syndrome.
Although the pathogenesis isn’t clearly understood, immature, nonfunctioning WBCs appear to accumulate first in the tissue where they originate. (Lymphocytes originate in lymph tissue; granulocytes originate in bone marrow.) These immature WBCs then spill into the bloodstream. From there, they infiltrate other tissues.
Complications
Acute leukemia increases the risk of infection and, eventually, organ malfunction through encroachment or hemorrhage.
Assessment
The patient’s history usually shows a sudden onset of high fever and abnormal bleeding, such as bruising after minor trauma, nosebleeds, gingival bleeding, purpura, ecchymoses, petechiae, and prolonged menses. He may also report fatigue and night sweats. More insidious
symptoms include weakness, lassitude, recurrent infections, and chills.
symptoms include weakness, lassitude, recurrent infections, and chills.
The patient with ALL, AML, or acute monoblastic leukemia may also complain of abdominal or bone pain. When assessing this patient, you may note tachycardia and, during auscultation, decreased ventilation, palpitations, and a systolic ejection murmur.
Inspection of any patient with acute leukemia may reveal pallor. On palpation, you may note lymph node enlargement as well as liver or spleen enlargement.
Diagnostic tests
Bone marrow aspiration showing a proliferation of immature WBCs confirms acute leukemia. If the aspirate is dry or free of leukemic cells but the patient has other typical signs of leukemia, a bone marrow biopsy—usually of the posterior superior iliac spine—must be performed. Blood counts show thrombocytopenia and neutropenia, and a WBC differential determines the cell type. Lumbar puncture detects meningeal involvement. A computed tomography scan shows the affected organs, and cerebrospinal fluid analysis detects abnormal WBC invasion of the central nervous system.
