[Photic sneeze reflex or autosomal dominant compelling helio-ophthalmic outburst syndrome].

Sneeze is an ubiquitous phenomenon that happens to everyone. In spite of this, little attention has been paid to it, among medical literature in general, and even less in neurologic texts. A curious entity, called photic sneeze reflex, solar sneeze reflex, light sneeze reflex or autosomal dominant compelling helio-ophthalmic outburst syndrome, known perhaps since ancient Greek, has been scarcely described in the scientific literature, mainly as clinical notes and letters to the editor, but in a detailed way, we can find just a few reports. This reflex appears when subjects are exposed suddenly to intense sunlight and it consists of long incoercible sneeze bursts. It is usually ignored by its sufferers, who report it as a curiosity or a minor complaint, and its importance has been neglected in spite of its hereditary nature and its apparently high prevalence. We review the history, epidemiology, genetics, neuroanatomy, neurophysiology and physiopathology of this reflex hereditary response.