In some cases, symptoms and physical findings of kernicterus appear two to five days after birth. Within the first few days of life, affected infants develop abnormally high levels of bilirubin in the blood (hyperbilirubinemia) and persistent yellowing of the skin, mucous membranes, and whites of the eyes (jaundice). Toxic levels of bilirubin may accumulate in certain areas of the brain (i.e., the basal ganglia and the brainstem), potentially resulting in a variety of symptoms and physical findings that, in some cases, may cause life-threatening complications.
Initial findings associated with kernicterus may vary from case to case, but often include lack of energy (lethargy) or drowsiness, poor feeding habits, fever, a shrill high-pitched cry, and/or absence of certain reflexes (e.g., Moro reflex, etc.). Affected infants may eventually experience respiratory distress, mild to severe Muscle spasms including those in which the head and heels are bent backward and the body bows forward (opisthotonus), and/or diminished muscle tone (hypotonia).
As an affected infants ages, other symptoms and physical findings may develop including delayed and/or abnormal motions or motor development; convulsions or seizures; impaired ability to coordinate voluntary movements (ataxia); abnormal muscle rigidity resulting in Muscle spasms (dystonia); slow, continuous, involuntary, writhing movements (athetosis) of the arms and legs (limbs) and/or entire body; problems with sensory perception; lack of upward gaze; and/or hearing loss. In some cases, affected infants may exhibit Mental retardation and Difficulty speaking (dysarthria). In most cases, the syndrome characteristic of kernicterus develops by three to four years of age.