A 60-Year-Old Man Comes to the Emergency Department Due to 10

question 66

Multiple Choice

A 60-year-old man comes to the emergency department due to 10 days of worsening cough, shortness of breath, and right-sided chest pain.  The patient also has had low-grade fever, fatigue, and unspecified weight loss.  A month ago, he was hospitalized for 2 days due to right lower lobe pneumonia.  Although oral antibiotics were prescribed at discharge, he did not get the prescription filled because his symptoms had improved.  Temperature is 38.2 C (100.8 F) , blood pressure is 116/70 mm Hg, pulse is 104/min, and respirations are 18/min.  Physical examination is notable for decreased breath sounds at the right lung base.  Chest imaging reveals loculated pleural fluid on the right side.  Laboratory analysis reveals the following: Blood cell counts were normal a month ago at the time of hospital discharge.  Which of the following is the most likely underlying cause of this patient's increased platelet count?

• A)Autonomous clonal proliferation of megakaryocytes
• B)Chronic hypoxia-induced erythropoietin release
• C)Cytokine-mediated megakaryocyte proliferation and maturation
• D)Decreased platelet sequestration by the spleen
• E)Increased platelet production from extramedullary hematopoiesis

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Definitions:

Allele

One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Blending Inheritance

An outdated theory of heredity proposing that the traits of offspring are a uniform blend of the parents' traits.

Dominant Alleles

Alleles that mask the effect of other alleles for the same gene in heterozygous individuals, determining the phenotype.

Recessive Alleles

Genetic variations that must be present in two copies (homozygous) to express a trait, as opposed to dominant alleles that require only one copy.