Definition

Leukemia is the uncontrolled production of leukocytes caused by cancerous mutation of lymphogenous cells or myelogenous cells. Lymphocytic leukemias begin in lymph nodes or other lymphogenous tissues and then spread to other areas of the body. Myeloid leukemias begin as cancerous production of myelogenous cells in bone marrow, with spread to extramedullary organs. Cancerous cells usually do not resemble other leukocytes and lack the usual functional characteristics of white blood cells. Leukemia cells may infiltrate the liver, spleen, and meninges and produce signs of dysfunction at these sites.

Incidence, pathophysiology, laboratory results, and treatment

Acute lymphoblastic leukemia accounts for approximately 15% of all leukemias in adults. Central nervous system dysfunction is common. These patients are highly susceptible to life-threatening infections, including those produced by Pneumocystis carinii (jiroveci) and cytomegalovirus.

Chronic lymphocytic leukemia accounts for approximately 25% of all leukemias and is most common in elderly men. The diagnosis is confirmed by the presence of lymphocytosis (>15,000/mm³) and lymphocytic infiltrates in bone marrow. There may be neutropenia with an associated increased susceptibility to bacterial infections. Treatment is with cancer chemotherapeutic drugs classified as alkylating agents.

Acute myeloid leukemia can result in death in about 3 months if untreated. Patients present with fever, weakness, bleeding, and hepatosplenomegaly. Chemotherapy produces a temporary remission in about half of patients.

Patients with chronic myeloid leukemia present with massive hepatosplenomegaly and white blood cell counts greater than 50,000/mm³. Fever and weight loss reflect hypermetabolism. Anemia may be severe. Splenectomy is routine in these patients.

Chemotherapy is the best available therapy for irradiation of cancerous cells anywhere in the body. Adverse clinical effects of these drugs include bone marrow suppression (susceptibility to infection, thrombocytopenia, and anemia), nausea, vomiting, diarrhea, ulceration of the gastrointestinal mucosa, and alopecia. Destruction of tumor cells by chemotherapy produces a uric acid load that may result in urate nephropathy and gouty arthritis. Bone marrow transplantation is also becoming an increasingly successful treatment for leukemia.