A 40-year-old man presents with 5 days of productive cough and fever. Pseudomonas aeruginosa is isolated from a pulmonary abscess. The CBC shows an acute effect characterized by marked leukocytosis (50,000 WBC/mL), and the differential count reveals numerous immature cells (band forms). Which of the following terms best describes these hematologic findings?

Leukemoid reaction. Circulating levels of leukocytes and their precursors may occasionally reach very high levels (>50,000WBC/mL). Such a situation, referred to as a leukemoid reaction, is sometimes difficult to differentiate from leukemia. In contrast to bacterial infections, viral infections (including infectious mononucleosis) are characterized by lymphocytosis, an absolute increase in the number of circulating lymphocytes. Parasitic infestations and certain allergic reactions cause eosinophilia, an increase in the number of circulating eosinophils. Leukopenia is defined as an absolute decrease in the circulating WBC count. Myloid metaplasia (choice C) and myeloproliferative disease (choice D) are chronic disorders of the hematopoietic system. Although technically correct, neutrophilia (choice E) by itself does not demonstrate immature cells (band forms) and usually refers to lower levels of increased neutrophils.Diagnosis: Pulmonary abscess