Genetic Spectrum of Cholestasis in Tunisia and Diagnostic Yield of Next-Generation Sequencing: Case Series of 70 Patients.

Cholestasis is caused by genetic disorders in 25% of cases. Our study aimed to describe the clinical and genetic profile of cholestasis and to demonstrate the importance of next-generation sequencing (NGS) in the etiologic diagnosis of genetic cholestasis. We included patients referred for cholestasis over a 10-year period. Molecular studies using NGS consisted of a 292-gene panel and/or whole exome sequencing. Our cohort included 70 patients from 66 unrelated families. A genetic diagnosis was established in 70% of the families. The most common diagnoses were Type 2 progressive familial intrahepatic cholestasis (n = 12), neonatal sclerosing cholangitis (n = 4), low phospholipid-associated cholelithiasis syndrome (n = 4), and Alagille syndrome (n = 4). The ABCB11 gene was most frequently mutated (15/46), with two recurrent variants, c.1062T>A (p.Tyr354*) and c.1826_1827dup (p.Ile610Glnfs*45), found in six and four families, respectively. Our results showed a 62% diagnostic yield of molecular testing using NGS in cholestasis. An accurate diagnosis was key to providing appropriate genetic counseling, guiding screening of variant carriers, and prenatal diagnosis.