Sickle cell disease (NORD) Quiz: Ace Your Exams

An 8-year-old African-American boy is brought to the clinic by his parents due to shortness of breath and  fatigue. The patient states that he first noticed the symptoms a couple months ago, but that they became much worse recently. He is diagnosed with a hemolytic condition, treated for his symptoms, and discharged. Over the following year, the symptoms worsen, and he presents to the hospital 3 more times with severe chest pain. Family history includes renal papillary necrosis in his paternal grandfather and sickle cell anemia in his maternal uncle. Current temperature is 37°C (98.9°F), pulse is 88/min, respirations are 18/min, and blood pressure is 116/74 mmHg. He is at the 40th percentile for height and 35th percentile for weight. Physical examination shows scleral icterus and splenomegaly. Laboratory tests are obtained and the results are shown below.  
 

Laboratory value	Result	Reference Range
Hematologic
Hemoglobin	8.3 g/dL	13.5-17.5 g/dL
Mean corpuscular volume (MCV)	96 fL	80-100 fL
Platelet count	210,000/mm3	150,000-400,000/mm3
Leukocyte count	9,500/mm3	4,500-11,000/mm3
Reticulocyte count	8.6%	0.5-1.5%

   
The patient is administered a medication that selectively inhibits ribonucleoside diphosphate reductase. Which of the following is most likely increased as a result of this patient’s treatment?