A 26-year-old woman comes to the emergency department with severe shortness of breath. She has a long history of asthma with periodic exacerbations. Her home medications include inhaled albuterol and fluticasone. The patient does not use tobacco, alcohol, or illicit drugs. Her temperature is 37.2 C (99 F), blood pressure is 150/90 mm Hg, pulse is 110/min, and respirations are 24/min. On examination, she has moderate respiratory distress, prolonged expiratory phase, and diffuse wheezing. Complete blood count shows a hemoglobin of 13.8 g/dL and a leukocyte count of 9,200/mm³. Chest x-ray reveals hyperinflated lungs but no infiltrates. The patient is admitted and is given nebulized albuterol, intravenous methylprednisolone, and supplemental oxygen. The next day, her respiratory status is improved. Repeat vital signs show temperature of 37.2 C (99 F), blood pressure of 130/80 mm Hg, pulse of 90/min, and respirations of 20/min. Some scattered bilateral wheezes are heard on lung auscultation. Changes in laboratory results are as follows: What is the most likely explanation for the abnormal laboratory findings in this patient?

Question

Quizplus · Accepted Answer

Explanation: This patient being treated for an asthma exacerbation now has leukocytosis with neutrophilic predominance, which is a common effect of systemic glucocorticoids (eg, methylprednisolone). Glucocorticoid use causes a leukocytosis due to the following: Mobilization of marginated neutrophils into the bloodstream (predominant mechanism): Marginated neutrophils are attached to the endothelium of blood vessels; glucocorticoid-induced mobilization of these neutrophils leads to a higher number of circulating neutrophils Stimulation of release of immature neutrophils from the bone marrow (as evidenced by the 3% band forms in this patient) Inhibition of neutrophil apoptosis In contrast, glucocorticoids decrease the number of circulating lymphocytes and eosinophils through a combination of increased apoptosis, increased emigration into the tissues, and decreased production. (Choice A) Hypersensitivity reaction is a potential cause of leukocytosis due to hypersensitivity-induced inflammation, but eosinophilia would be expected. (Choice C) There is no evidence to suggest a metabolic disorder (eg, ketoacidosis, poisoning) as the cause of the leukocytosis in this patient. (Choice D) A myeloproliferative disorder causing an abrupt leukocytosis in this young patient would be extremely unlikely, especially given the lack of immature forms on peripheral smear. (Choice E) This patient's presentation with dyspnea, wheezing, prolonged expiratory phase, and hyperinflation on chest x-ray is consistent with an asthma exacerbation. Pneumonia is unlikely as there is no cough, fever, or infiltrates on chest x-ray. Educational objective: Glucocorticoids cause a leukocytosis mainly through mobilization of marginated neutrophils and an increase in the number of circulating neutrophils. References: Prednisone-induced leukocytosis. Influence of dosage, method and duration of administration on the degree of leukocytosis. (http://www.ncbi.nlm.nih.gov/pubmed/7304648)

A 26-Year-Old Woman Comes to the Emergency Department with Severe