# Beyond the Pump: The Evolving Molecular Landscape of Intrahepatic Cholestasis

## TL;DR

This paper reviews how genetics is changing the understanding and treatment of cholestatic liver diseases, linking specific genetic defects to new targeted therapies.

## Contribution

The paper presents a new framework for cholestasis as a continuous spectrum and highlights the role of genetics in diagnosis and treatment.

## Key findings

- Genetic analysis has expanded the classification of intrahepatic cholestasis to 13 distinct types.
- Next-Generation Sequencing is now preferred over liver biopsy for diagnosing cholestatic diseases.
- Specific genetic profiles determine eligibility for targeted therapies like IBAT inhibitors.

## Abstract

Cholestasis encompasses a broad spectrum of hepatobiliary disorders characterized by impaired bile formation or flow. Historically classified based on clinical onset and severity, the landscape of cholestatic liver disease has been revolutionized by the advent of high-throughput genomic technologies. This review elucidates the critical role of genetics in redefining the pathophysiology, diagnosis, and management of cholestasis, framing pediatric Progressive Familial Intrahepatic Cholestasis (PFIC) and Adult-Onset Cholestatic Disease (AOCD) as a continuous phenotypic spectrum. We discuss the expansion of the molecular nosology to include 13 distinct PFIC types, highlighting how defects in canalicular transporters, tight junctions, and nuclear receptors underpin clinical heterogeneity. Furthermore, we examine the paradigm shift in the diagnostic flowchart, where Next-Generation Sequencing (NGS) has largely superseded liver biopsy for etiological definition. Finally, we address the therapeutic implications of this molecular precision, demonstrating how specific genotypes dictate eligibility for novel targeted therapies, such as IBAT inhibitors, marking the transition from supportive care to personalized medicine.