Gastrointestinal · Year 2 · from Gastrointestinal
Case 3: Gilbert Syndrome
Patient Presentation
Demographics: 22-year-old male college student
Chief Complaint: Intermittent yellow eyes noticed by friends
History of Present Illness: The patient's roommates have commented that his eyes "look yellow" occasionally, particularly during finals week or when he has been sick. He reports no abdominal pain, change in stool color, or dark urine. He feels well between episodes. He recently had a viral upper respiratory infection and noticed his eyes became more yellow.
Past Medical History: Mononucleosis 2 years ago (recovered without complications)
Family History: Father has "the same thing" with occasional yellow eyes
Social History: College student, occasional alcohol at parties, no medications, no supplements
Physical Examination
- Vital Signs: Normal
- General: Healthy-appearing young male with mild scleral icterus
- Abdomen: Soft, non-tender, no hepatomegaly, no splenomegaly
- Skin: Faint jaundice, no pruritus marks
Workup and Results
- Liver Function Tests: Total bilirubin 3.8 mg/dL, indirect (unconjugated) bilirubin 3.4 mg/dL, direct bilirubin 0.4 mg/dL; AST 22 U/L, ALT 25 U/L, ALP 68 U/L (all normal)
- CBC: Hemoglobin 14.8 g/dL, reticulocyte count normal (rules out hemolysis)
- Haptoglobin: Normal
- LDH: Normal
- Fasting Bilirubin (48-hour fast provocation): Rose to 5.2 mg/dL (characteristic increase with fasting)
Diagram illustrating bilirubin metabolism in Gilbert syndrome, showing reduced activity of UGT1A1 enzyme leading to unconjugated hyperbilirubinemia without liver disease or hemolysis.
Image Source: Adapted from educational materials
Diagnosis
Gilbert Syndrome
Clinical Correlation to Bilirubin Metabolism
Gilbert syndrome is a benign condition affecting 5-10% of the population, caused by reduced activity of UDP-glucuronosyltransferase 1A1 (UGT1A1), the hepatocyte enzyme that conjugates bilirubin with glucuronic acid. A promoter region polymorphism (TA repeat) in the UGT1A1 gene reduces expression to approximately 30% of normal. This is sufficient for normal bilirubin handling under basal conditions but becomes limiting during physiologic stress (fasting, illness, exercise). The unconjugated hyperbilirubinemia is harmless because bilirubin levels rarely exceed 5 mg/dL, far below neurotoxic thresholds. The normal aminotransferases and alkaline phosphatase exclude liver disease. The absence of hemolysis markers (normal reticulocytes, LDH, haptoglobin) excludes prehepatic causes.
Treatment
- No treatment required - this is a benign condition
- Reassurance and education: episodes are expected during stress, illness, or fasting
- Avoid prolonged fasting
- Genetic counseling not typically needed (benign condition)
- Note in medical record to avoid unnecessary workup in future
- Relevant for drug metabolism: reduced UGT1A1 affects clearance of some drugs (e.g., irinotecan toxicity risk)