Imaging description

A six-year-old male presented with hyponatremia and hyperpigmentation. MRI of the brain was obtained which showed abnormal FLAIR signal within the splenium of the corpus callosum (Fig. 8.1a). Sagittal and axial postcontrast T1-weighted images demonstrated prominent zonal enhancement along the anterior margin of the lesion (Fig. 8.1b, c).The findings were strongly suggestive of adrenoleukodystrophy.

Importance

X-linked adrenoleukodystrophy (XALD) is a genetic disorder affecting the adrenal cortex and the central nervous system (CNS) with wide phenotypic variability. XALD is caused by mutations in the ABCD1 gene located on chromosome Xq28 which encodes a peroxisomal membrane transporter protein (XALDP). This mutation causes accumulation of saturated very long chain fatty acids in all tissues, especially CNS white matter and adrenal cortex. As such, XALD is considered within the general category of peroxisome disorders.

The pathologic abnormalities in the brain consist of widespread demyelination of the white matter. In most cases, the process starts in the splenium of the corpus callosum and spreads bilaterally to the occipital and parietal periventricular regions. Histopathologic examination reveals different zones of demyelination within the affected brain, with anterior zones demonstrating active inflammatory demyelination, while posterior zones appear destroyed and burnt out.