A 29-year-old woman is found, on routine annual blood testing, to have a small increase in unconjugated bilirubin. There is no evidence of hemolysis and her liver enzymes and function tests are otherwise normal. She has no prior history of liver disease and is not taking any medications. Her physical examination is completely normal with no signs of chronic liver disease. Which of the following is the most likely diagnosis?

## **Core Concept**
The question describes a scenario where a patient has an isolated increase in unconjugated bilirubin levels without any evidence of hemolysis, liver dysfunction, or other abnormalities. This presentation suggests a condition affecting the uptake or processing of bilirubin in the liver.

## **Why the Correct Answer is Right**
The most likely diagnosis in this case is **Gilbert syndrome**. Gilbert syndrome is a benign genetic disorder characterized by mildly elevated levels of unconjugated bilirubin in the blood, particularly during fasting or illness. It results from a partial deficiency of the enzyme **UDP-glucuronyltransferase** (UGT), which is necessary for converting unconjugated bilirubin into conjugated bilirubin. This condition does not lead to liver dysfunction or structural damage and is consistent with the patient's normal liver enzymes, lack of hemolysis, and absence of other symptoms.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, conditions like **Crigler-Najjar syndrome** could be considered. However, Crigler-Najjar syndrome presents with much higher levels of unconjugated bilirubin and often leads to kernicterus in newborns, which does not fit this patient's mild presentation.
- **Option B:** Similarly, not provided, but another differential could be **hemolytic anemia**. However, the question explicitly states there is no evidence of hemolysis, making this option incorrect.
- **Option D:** Without the specific details of option D, another potential differential could be **chronic liver disease**. However, the patient's normal liver enzymes, lack of signs of liver disease on physical examination, and absence of a history of liver disease make this option unlikely.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **Gilbert syndrome** is a common, benign condition that can cause mild increases in unconjugated bilirubin levels. It is often discovered incidentally during routine blood tests and does not require treatment. A classic feature is that bilirubin levels may increase during fasting or with illness, which can help distinguish it from other causes of elevated bilirubin.

## **Correct Answer:** . **Gilbert syndrome**

✓ Correct Answer: D. Gilbert syndrome