A 4-month-old boy is brought to the office due to abnormal twisting movements of the limbs and torso. The patient also is not able to push up on his arms when prone. He was born at full term to a 30-year-old woman by forceps-assisted vaginal delivery. The delivery was complicated by cephalohematoma. The patient has not been evaluated since discharge at age 2 days. Vital signs are normal. Weight and length are at the 50th percentile for age. His eyes are crossed, and he does not react to sound. Dystonic extremities are noted on examination. Which of the following is the most likely explanation for this patient's current condition?
Bilirubin-induced neurologic dysfunction | |
Pathophysiology |
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Risk factors |
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Acute |
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Chronic |
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This infant who was not evaluated beyond the immediate newborn period now has dystonic movements (ie, involuntary twisting/writhing), a finding concerning for bilirubin-induced neurologic dysfunction (BIND). BIND occurs when bilirubin concentration dramatically rises (total bilirubin ≥30 mg/dL) and exceeds the binding capacity of albumin. Unbound bilirubin crosses the blood-brain barrier and deposits in the basal ganglia and brainstem nuclei (eg, oculomotor, auditory), causing neuronal damage.
Although many patients have no known risk factors, the cephalohematoma this patient sustained during delivery likely led to localized red blood cell breakdown that caused unconjugated hyperbilirubinemia.
Acute BIND typically presents with lethargy; tone abnormalities; and high-pitched, inconsolable crying. However, symptoms may be subtle or overlooked.
Prolonged, unrecognized or untreated hyperbilirubinemia can lead to chronic BIND (ie, kernicterus), typically presenting after early infancy with irreversible neurologic damage. Common manifestations include hyperkinetic movements (eg, choreoathetosis, dystonia), sensorineural hearing loss, and abnormal eye movements (eg, upward gaze palsy). Developmental delay (eg, inability to push up when prone at age 4 months) is also typical.
Serial examinations and/or bilirubin monitoring in the early neonatal period, particularly in patients with risk factors, as well as early treatment of hyperbilirubinemia (eg, phototherapy) can help prevent BIND.
(Choice A) Autoimmune injury to the basal ganglia describes Sydenham chorea, a manifestation of acute rheumatic fever (ARF). This complication of an untreated Streptococcus pyogenes infection typically presents at age 5-15, not in infancy. None of the other ARF findings (eg, fever, rash, arthritis) is present in this case, and the patient's hearing loss and gaze abnormality are inconsistent with the diagnosis.
(Choice C) MECP2 gene mutation causes Rett syndrome, a disorder characterized by speech regression, abnormal gait, and loss of purposeful hand movements (eg, repetitive hand wringing). It also is a condition that affects girls, and neurologic degeneration begins after age 6 months.
(Choice D) Physiologic chorea of infancy refers to benign, chorea-like movements in normal newborns. It resolves by age 8 months. Neither hearing loss nor gaze abnormalities are seen.
(Choice E) Huntington disease, caused by a trinucleotide repeat expansion on chromosome 4p, typically presents in adulthood with chorea (ie, involuntary, jerky movements) and progressive dementia. This patient's age excludes the diagnosis.
Educational objective:
Bilirubin-induced neurologic dysfunction is due to extreme unconjugated bilirubinemia in which unbound bilirubin crosses the blood-brain barrier. Chronic disease (ie, kernicterus) results in hyperkinetic movements (eg, chorea, dystonia), sensorineural hearing loss, and gaze abnormalities.