Kernicterus is a rare but serious condition that occurs in newborns when there is a high level of bilirubin in the blood. Bilirubin is a yellow substance produced during the breakdown of red blood cells. If not treated, excessive bilirubin can cross the blood-brain barrier and cause damage to the brain, leading to severe neurological issues. Symptoms of Kernicterus may include lethargy, poor feeding, and abnormal muscle tone. Early detection and treatment of high bilirubin levels, often through phototherapy or exchange transfusion, are crucial to prevent this condition. Long-term effects can include hearing loss, vision problems, and movement disorders.