An 18-year-old man presents for a screening physical exam to join his college freshman lacrosse team. He reports no medical problems and does not take any medications. The physical exam is unremarkable. His immunizations are up-to-date, and he denies sexual activity or smoking. A review of routine labs reveals an elevation in unconjugated bilirubin. Liver enzymes, serum electrolytes, complete blood count, and conjugated bilirubin level are within normal limits. What is the most likely diagnosis for the 18-year-old man with an elevation in unconjugated bilirubin?

a) Gilbert syndrome
b) Hemolytic anemia
c) Cirrhosis
d) Hepatitis

The most likely diagnosis for the young man's elevated unconjugated bilirubin is Gilbert syndrome, due to the absence of other symptoms and normal liver enzymes.

Explanation:

The most likely diagnosis for the 18-year-old man with an elevation in unconjugated bilirubin is Gilbert syndrome. Gilbert syndrome is a mild liver condition where there is a defect in the uptake of bilirubin by the liver, due to slightly lowered activity of the enzyme UDP-glucuronyl transferase. This leads to a mild increase in unconjugated bilirubin in the bloodstream. Other conditions such as hemolytic anemia, cirrhosis, or hepatitis are less likely since liver enzymes, serum electrolytes, complete blood count, and conjugated bilirubin levels are within normal limits, and there are no other symptoms present.