Retinal dysfunction in a presymptomatic patient with Huntington's disease

Huntington's disease (HD) is an autosomal dominant, neurodegenerative disorder characterized by progressive motor dysfunction, cognitive decline, and psychiatric disturbances. Studies have shown retinal abnormalities in patients and mouse models with HD; however, to our knowledge, no prior research papers evaluated retinal structure and function in a presymptomatic patient with HD. The aim of this report is to present a case of retinal dysfunction in a presymptomatic patient with HD. We investigated retinal structure and function in a 25-year-old male who tested positive for the gene that causes HD, but did not have any symptoms normally associated with HD. Vision and ocular testing included a comprehensive dilated ophthalmic examination, 24-2 full-threshold Humphrey visual field, spectral-domain optical coherence tomography (SD-OCT), fundus photography, full-field electroretinogram (ERG), and multifocal electroretinogram (mfERG). Visual electrophysiology testing showed rod and cone functional anomalies in both eyes. Full-field ERG amplitudes were subnormal in both eyes for the dark-adapted (DA) 0.01 ERG, DA 3 ERG, DA 3 oscillatory potentials (OPs), DA 10 ERG, light-adapted (LA) 3 ERG, and LA 30 Hz flicker, but peak times for the six standard ERG responses were not significantly different from normals. mfERGs revealed functional anomalies of the central retina with attenuated P1 amplitudes for five of the six concentric rings in the right eye and all six rings in the left eye. mfERG P1 peak times were normal at all eccentricities. Dilated fundus examination, SD-OCT, and fundus photography were unremarkable in both eyes. The visual field was normal in the right eye, but there was a mild paracentral field defect in the left eye. Our results illustrate that the ERG and mfERG detected early retinal dysfunction in a presymptomatic patient with HD consistent with electroretinogram findings in animal models of HD. However, our report was limited to one patient and additional studies are needed to verify whether the ERG and/or mfERG can uncover neural dysfunction before motor, behavioral, and cognitive abnormalities are discernible in patients with HD.