Crigler-Najjar syndrome type 2 complicating cholecystitis in a patient with UGT1A1 gene double homozygous mutations
Higher Education PressCrigler-Najjar syndrome (CNS) and Gilbert syndrome (GS) are rare autosomal recessive disorders causing unconjugated hyperbilirubinemia due to reduced UGT1A1 enzyme activity, with CNS type 2 (CNS2) carrying a higher risk of gallbladder stones and cholecystitis than the typically benign GS. This case report details a 28-year-old male patient with recurrent right upper abdominal pain and lifelong persistent jaundice, diagnosed with CNS2 complicated by gallbladder stones and cholecystitis after genetic testing revealed rare double homozygous mutations—A(TA)₇TAA (rs3064744) and P229Q (rs35350960)—in the UGT1A1 gene. Pedigree analysis showed the patient’s parents, who had mildly elevated bilirubin levels, carried compound heterozygous mutations of the same two variants and were diagnosed with GS. Bioinformatics analysis indicated A(TA)₇TAA, located in the UGT1A1 promoter’s TATA-box region, impairs gene transcriptional initiation, while P229Q alters the protein’s three-dimensional structure and is likely pathogenic. The double homozygous mutations in the patient resulted in a more severe phenotype than the compound heterozygous mutations in his parents. The case highlights the need to suspect inherited hyperbilirubinemia causes after ruling out biliary obstruction, and suggests early bilirubin reduction (to < 103 μmol/L (6 mg/dL)) may lower CNS2 patients’ risk of complications like cholecystitis, though longer follow-up studies are required to confirm this.
- Journal
- Frontiers of Medicine