Optic disk and white matter abnormalities in a patient with a de novo 18p partial monosomy

Purpose: Neuro-ophthalmologic and neuroimaging features of partial chromosome 18p deletion syndromes have not yet been fully described. Methods: Careful neuro-ophthalmologic and neuroimaging evaluation of a young woman with a partial 18p deletion, including 3 Tesla MRI and diffusion tensor imaging, cytogenetic analysis on GTG-banded chromosomes, and 244K array CGH analysis. Results: This 17-year-old girl had modest mental retardation, facial dysmorphism, other characteristics typical of 18p deletion syndrome, and anomalous optic disks. MRI showed enlarged third and lateral ventricles, a thin corpus callosum and patchy white matter signal hyperintensities without enhancement, while diffusion tensor imaging (DTI) revealed significant abnormalities of the corpus callosum with relative sparing of the corticospinal tracts. She had a de novo 14.6Mb deletion on chromosome 18p [del(18)(p11. 2>pter)], a region including 143 genes, only 10 of which were likely candidates for phenotypic expression. Conclusions: This young woman had clinical features similar to those described previously with the 18p deletion syndrome, including moderate mental retardation and dysmorphism without focal neurologic signs. She was myopic, like other 18p deletion patients, supporting the concept that 18p contains a candidate locus for myopia. She also had anomalous optic disks, a feature that may be more common in this syndrome than previously recognized. MRI revealed enlarged ventricles and white matter abnormalities that may be explained in part by haploinsufficiency of ADCYAP1 and LPIN2 in the deleted region of chromosome 18.