X-linked infantile periodic alternating nystagmus.

Objective: To describe the clinical and electrophysiological characterization of four family members from three generations who have X-linked infantile periodic alternating nystagmus (XIPAN).
Methods: Complete clinical ophthalmological evaluation, pedigree analysis, electroretinograms (ERG), eye movement recordings (EMR), color vision, and fundus photography were performed on all subjects.
Results: Three males in two generations and one female were examined. Clinical examinations showed a jerk/pendular nystagmus with a latent component, strabismus, and a significant refractive error in the three affected males, while the female had only myopic astigmatism. ERG, color contrast, and fundus examinations were normal in all four family members. All four family members showed EMR abnormalities with infantile jerk/dual jerk and pendular nystagmus waveforms. The female had nystagmus present on EMR only and all patients showed (a)periodicity to their nystagmus.
Conclusions: In this family with no other congenital visual sensory system disease, affected males had obvious periodic alternating nystagmus, strabismus, and refractive errors, while the female had clinically "silent" periodic nystagmus that is probably a marker for the carrier state.