A 45-year-old man comes to the office due to a week of purulent nasal discharge, headache, sore throat, and nonproductive cough. He has no significant past medical history except for an episode of infectious mononucleosis at age 22. The patient smokes a pack of cigarettes daily. His temperature is 38 C (100.4 F). He has maxillary sinus tenderness, pharyngeal erythema, and tender anterior cervical lymphadenopathy. Laboratory results are as follows: The leukocyte alkaline phosphatase score is low. Which of the following is the most likely diagnosis?

Question

A 45-year-old man comes to the office due to a week of purulent nasal discharge, headache, sore throat, and nonproductive cough.  He has no significant past medical history except for an episode of infectious mononucleosis at age 22.  The patient smokes a pack of cigarettes daily.  His temperature is 38 C (100.4 F).  He has maxillary sinus tenderness, pharyngeal erythema, and tender anterior cervical lymphadenopathy.  Laboratory results are as follows:  The leukocyte alkaline phosphatase score is low.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_3972_aa45_9249_b5bf4aa00e82_MD0001_00 This patient with sinusitis is found to have a markedly elevated white blood cell (WBC) count with an increase in myeloid precursor forms on peripheral blood smear. The differential diagnosis is chronic myelogenous leukemia (CML) (uncontrolled mature granulocyte production, mostly neutrophils but also basophils and eosinophils) or leukemoid reaction (over-exuberant WBC response associated with bacterial infection or malignancy, among others). Both cause an elevated WBC count (>50,000/mm³) with an increase in precursor forms (eg, bands, metamyelocytes, myelocytes). However, the enzyme leukocyte (neutrophil) alkaline phosphatase is decreased in CML (as seen in this patient) because the WBCs are cytochemically abnormal; by contrast, it is normal or elevated in a leukemoid reaction (Choice I). Other clues to the diagnosis of CML are the predominance of myelocytes compared to more mature forms such as metamyelocytes ("myelocytic bulge") and the absolute basophilia and eosinophilia. CML is confirmed by demonstration of the Philadelphia chromosome (translocation between chromosomes 9 and 22) or the BCR-ABL1 fusion gene or mRNA. Immature blast cells (eg, myeloblasts, promyelocytes) are typically <2%. Management generally includes a tyrosine kinase inhibitor. (Choice A) This patient has an abnormality of myeloid (not lymphoid) cells and his smear shows only 1% blasts. In general, >25% bone marrow lymphoblasts are seen in acute lymphoblastic leukemia, which is much more common in young children. (Choice B) Acute myelogenous leukemia is the most common acute leukemia in adults. However, the mean age at diagnosis is around 65, and most patients will have a WBC count of about 15,000-20,000/mm³ with a significant increase in blast cells (eg, >20%) rather than the 1% seen in this patient. (Choices C, F, and G) Follicular lymphoma, Burkitt lymphoma, and diffuse large B-cell lymphoma cause lymph node and/or soft-tissue (not peripheral blood) abnormalities. In addition, these cancers are all lymphoid, not myeloid, in nature. (Choice D) Patients with chronic lymphocytic leukemia have increased circulating mature lymphoid cells, not increased myeloid cells. (Choices H and J) Parasitic superinfection (which can lead to eosinophilia) and fungal infection would not explain the predominance of myeloid neutrophil precursor forms in this patient. Educational objective: Chronic myelogenous leukemia (CML) and leukemoid reaction can have presentations similar to leukocytosis; however, leukocyte (neutrophil) alkaline phosphatase level is normal or elevated in a leukemoid reaction but decreased in CML. The definitive diagnosis of CML requires demonstration of the Philadelphia chromosome t(9;22) or BCR-ABL fusion gene or mRNA. __________ References: How I treat newly diagnosed chronic myeloid leukemia in 2015. (http://www.ncbi.nlm.nih.gov/pubmed/25370814)

A 45-Year-Old Man Comes to the Office Due to a Week