Multimodality neuroimaging findings in chromosome 18p deletion extending to 18q12.3: MRI features of developmental white matter abnormality suggestive of hypomyelination

Abstract Chromosome 18 deletions are rare genomic disorders associated with heterogeneous neurologic and structural abnormalities. Neuroimaging findings in deletions extending from the short arm into the proximal long arm remain incompletely characterized. We report multimodality neuroimaging findings in a pediatric patient with cytogenetically confirmed 46, XX, del(18)(pter→q12.3). Clinical manifestations included global developmental delay, progressive microcephaly, congenital hypothyroidism, bilateral sensorineural hearing loss, atrial septal defect, and progressive left equinovarus deformity. Cranial ultrasonography demonstrated lenticulostriate vasculopathy, and CT showed minimal nonspecific basal ganglia hypodensity. Brain MRI revealed diffuse supratentorial white matter T2 hyperintensity with relative preservation of T1 gray–white differentiation, suggestive of a developmental hypomyelination phenotype, along with corpus callosum thinning, mild cerebral volume loss, and mild reduction in pontine volume. Imaging findings remained stable without evidence of progressive leukodystrophy. Notably, the deletion did not extend to the distal 18q23 region containing the myelin basic protein locus, suggesting that hypomyelination may occur in proximal 18q deletions independent of distal gene loss. This case underscores the central role of MRI in characterizing genetic white matter disorders and differentiating hypomyelination from leukodystrophy and acquired injury.