From Childhood Icterus to Adolescent Gallstones: Clinically Diagnosed Crigler‐Najjar Syndrome Type <scp>II</scp>

Crigler-Najjar syndrome type II (CNS-II) is an uncommon cause of persistent unconjugated hyperbilirubinemia resulting from partial deficiency of hepatic UDP-glucuronosyltransferase activity. We report the case of a 19-year-old male who presented with intermittent jaundice since childhood and recent worsening of scleral icterus. Laboratory evaluation revealed isolated unconjugated hyperbilirubinemia with normal liver enzymes. Genetic testing was unavailable; however, serum bilirubin levels declined significantly following phenobarbital therapy, confirming the diagnosis of CNS-II. Abdominal ultrasonography demonstrated gallstones, indicating chronic bilirubin supersaturation secondary to longstanding hyperbilirubinemia. The patient was managed conservatively with phenobarbital and counseling on avoiding precipitating factors such as fasting and hepatotoxic drugs. This case underscores the importance of recognizing CNS-II as a differential diagnosis in young adults with isolated unconjugated hyperbilirubinemia and cholelithiasis. It also highlights phenobarbital responsiveness as a valuable diagnostic tool in settings lacking molecular testing.