Hereditary primary lateral sclerosis with cone dysfunction

To describe the clinical phenotype and electroretinographic changes in two siblings with primary hereditary lateral sclerosis.

Case series of two male siblings from a consanguineous family. A clinical evaluation and full field electroretinography according to International Society for Clinical Electrophysiology of Vision (ISCEV) standards was performed.

Both siblings had reduced central vision without nystagmus and a normal fundus examination. The electroretinogram showed cone dysfunction with markedly reduced amplitude 30-Hz flicker, and broad, delayed photopic single flash of normal amplitude. The rod driven electroretinography (ERG) b-waves were within the normal range.

Cone dysfunction has not been reported previously in patients with primary lateral sclerosis. Although it is possible this is a chance association it is more likely that the retinal dysfunction is caused by the same genetic mutation causing the neurological disease. Investigation of other cases will be helpful in delineating the phenotype. The association may also help prioritize candidate gene analysis in the search for the underlying genetic mutation causing primary lateral sclerosis.