# From Childhood Icterus to Adolescent Gallstones: Clinically Diagnosed Crigler‐Najjar Syndrome Type II

## TL;DR

A young man with lifelong jaundice and gallstones was diagnosed with a rare liver metabolism disorder using a drug response test.

## Contribution

Demonstrates phenobarbital responsiveness as a diagnostic tool for CNS-II in settings without genetic testing.

## Key findings

- Phenobarbital therapy significantly reduced bilirubin levels, confirming CNS-II diagnosis.
- Chronic hyperbilirubinemia led to gallstone formation in a CNS-II patient.
- Phenobarbital responsiveness can serve as a diagnostic marker in resource-limited settings.

## Abstract

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.

This case highlights an uncommon adult presentation of Crigler–Najjar syndrome type II, complicated by cholelithiasis, underscoring the need to consider inherited disorders of bilirubin metabolism in persistent unconjugated hyperbilirubinemia. Recognizing phenobarbital responsiveness remains crucial for diagnosis in resource‐limited settings where genetic testing is not readily available.