Congenital-type nystagmus emerging in later life.

We describe six patients who, as teenagers or adults, developed florid nystagmus with consequent visual symptoms without any other manifestation of disease. In three patients, previous ophthalmologic examination had excluded nystagmus, and there was medically informed witness to its onset. The remainder may or may not have had a milder, unsuspected nystagmus before the development of symptoms. Ophthalmologic and neurologic investigations were negative, and follow-up of 2 to 15 years has been uneventful. Eye movement recordings showed the characteristics of the nystagmus to be indistinguishable from congenital nystagmus, which normally becomes manifest in early infancy. We conclude that a congenital-type nystagmus can emerge or enhance in later life without apparent provocation and is probably associated with a benign pathophysiology.