Novel Cause of Reversible Leukoencephalopathy in an Infant Associated With Illicit Fentanyl Exposure.

Fentanyl is a potent opioid anesthetic and analgesic whose illicit use has been linked to a significant increase in mortality and morbidity, affecting not only adults but also children through accidental exposure. We present a case of a 12-month-old normally developing baby girl who was admitted for hypothermia, acute hypoxic respiratory failure, altered mental status, and metabolic acidosis. A comprehensive workup confirmed the presence of fentanyl in her urine. A magnetic resonance image (MRI) of the brain revealed multiple areas of signal abnormalities in the subcortical and periventricular white matter. The infant recovered and was discharged with an age-appropriate neurologic examination. A repeat MRI at 18 months showed almost complete resolution of the previous findings along with a normal neurologic exam and development for age. This case emphasizes the importance of timely diagnosis and appropriate management in preventing long-term neurologic sequelae associated with fentanyl exposure.