Short answer · Medically reviewed summary · Last updated: 2026-04-06

Alagille syndrome is a multisystem genetic disorder characterized by a reduction in the number of bile ducts in the liver, which leads to cholestasis, alongside potential abnormalities in the heart, skeleton, eyes, and kidneys. Understanding Alagille Syndrome Alagille syndrome is a rare, autosomal dominant condition, meaning it is typically caused by a mutation in a single gene—most commonly the JAG1 gene, and less frequently the NOTCH2 gene. These genes are vital for the Notch signaling pathway, which tells cells how to develop and communicate during fetal growth.

What is Alagille Syndrome

Name: What is Alagille Syndrome
Creator: DiseaseMaps Editorial Team
Published: 2015-06-17UTC01:53:19.0000000

What is Alagille Syndrome? Plain-language, medically reviewed definition plus the lived reality told by patients.

Understanding Alagille Syndrome

Alagille syndrome is a rare, autosomal dominant condition, meaning it is typically caused by a mutation in a single gene—most commonly the JAG1 gene, and less frequently the NOTCH2 gene. These genes are vital for the Notch signaling pathway, which tells cells how to develop and communicate during fetal growth. Because this pathway is essential for many organs, the impact of Alagille syndrome is widespread.

Body Systems Affected

The clinical presentation of Alagille syndrome varies significantly even among family members. Key systems involved include:

Liver: The hallmark is "paucity of bile ducts," where the small bile ducts within the liver are underdeveloped or reduced in number, causing bile to build up and potentially damage the liver.

Heart: Pulmonary artery stenosis (narrowing of the vessels carrying blood to the lungs) is the most common cardiac manifestation.

Skeleton: Many individuals exhibit "butterfly vertebrae," a distinct fusion abnormality of the spine visible on X-rays.

Eyes/Kidneys: Posterior embryotoxon (a visible ring in the eye) is common, as are various structural kidney issues.

Prevalence and Classification

The estimated prevalence of Alagille syndrome ranges from 1 in 30,000 to 1 in 50,000 live births. It affects males and females equally and shows no specific geographic or ethnic predisposition. While there are no formal "subtypes," the disease is classified by the broad spectrum of its severity; some individuals may have only mild liver involvement, while others experience profound cardiac or hepatic complications. It is distinguished from other cholestatic liver diseases by its multisystem involvement, particularly the combination of heart murmurs, specific facial features (such as a prominent forehead and deep-set eyes), and spinal findings.

Medical Disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions regarding a medical condition.