X-Linked Cerebral Adrenoleukodystrophy Presenting With Acute Encephalitis-Like Illness and Optic Neuropathy in a Child.

An 8-year-old boy was found unconscious after febrile gastroenteritis. Upon arrival to the emergency department, he was unresponsive with fixed dilated pupils, high fever, tachycardia, and severe hypoxia. Brain computed tomography followed by brain MRI revealed diffuse cerebral edema with tonsillar herniation. He was treated with mannitol, hypertonic saline, broad-spectrum antimicrobials, and corticosteroids, resulting in rapid systemic recovery. Four months later, follow-up MRI revealed new nonenhancing hyperintense lesions involving optic nerves, chiasm and tracts, and subtle midbrain lesions. Ophthalmologic examination revealed profound vision loss, bilateral optic disc pallor and marked thinning of the retinal nerve fiber and ganglion cell layers on optical coherence tomography. An infectious and autoimmune workup, including anti-MOG and anti-AQP4 antibodies, was negative. Seronegative autoinflammatory demyelinating disease was suspected, and treatment with high-dose steroids and plasmapheresis yielded only mild visual improvement. Monthly intravenous immunoglobulin led to subjective and objective gains. A subsequent MRI demonstrated progression of midbrain lesions. Given the MRI findings and the atypical disease course, genetic testing was performed, identifying a pathogenic ABCD1 mutation and confirming X-linked cerebral adrenoleukodystrophy, following which the patient underwent allogeneic hematopoietic stem cell transplantation.