Exome sequencing in familial corticobasal degeneration

Background: Corticobasal degeneration (CBD) is a neurodegenerative, sporadic disorder of unknown cause. Few familial cases have been described. Objective: We aim to characterize the clinical, imaging, pathological and genetic features of two familial cases of CBD. Methods: We describe two first cousins with CBD associated with atypical MRI findings. We performed exome sequencing in both subjects and in an unaffected first cousin of similar age. Results: The cases include a 79-year-old woman and a 72-year-old man of Native American and British origin. The onset of the neurological manifestations was 74 and 68 years respectively. Both patients presented with a combination of asymmetric parkinsonism, apraxia, myoclonic tremor, cortical sensory syndrome, and gait disturbance. The female subject developed left side fixed dystonia. The manifestations were unresponsive to high doses of levodopa in both cases. Extensive bilateral T1-W hyperintensities and T2-W hypointensities in basal ganglia and thalamus were observed in the female patient; whereas these findings were more subtle in the male subject. Postmortem examination of both patients was consistent with corticobasal degeneration; the female patient had additional findings consistent with mild Alzheimer's disease. No Lewy bodies were found in either case. Exome sequencing showed mutations leading to possible structural changes in MRS2 and ZHX2 genes, which appear to have the same upstream regulator miR-4277. Conclusions: Corticobasal degeneration can have a familial presentation; the role of MRS2 and ZHX2 gene products in CBD should be further investigated.