What is the mode of inheritance for Crigler-Najjar Syndrome?

Crigler-Najjar Syndrome is characterized as an autosomal recessive genetic disorder. This syndrome arises due to mutations in the UGT1A1 gene, which is essential for the conjugation of bilirubin. In this condition, both copies of the gene (one inherited from each parent) must be mutated for the disease to manifest, leading to severely elevated levels of unconjugated bilirubin in the blood. Because it is autosomal recessive, an individual must inherit two defective copies of the gene—one from each parent—to express the condition.

Individuals who possess only one normal copy of the gene typically do not exhibit any symptoms and can be considered carriers. This inheritance pattern is crucial to understanding the risk of the disorder appearing in siblings of affected individuals, as there is a 25% chance that siblings will inherit the syndrome if both parents are carriers. The other modes of inheritance listed, such as autosomal dominant, X-linked recessive, and mitochondrial inheritance, do not apply to Crigler-Najjar Syndrome, as their patterns do not accurately reflect the genetic transmission observed for this disorder.