X linked retinoschisis.

X-linked retinoschisis (MIM#312700) is linked to mutations in RS1 encoding retinoschisin a protein critical for cell-cell adhesion and intercellular matrix interactions. It is a rare inherited disorder with a prevalence estimated between 1/5,000 and 1/20,000, affecting male subjects with female carriers being asymptomatic with only few reports of subtle changes. Age of onset can be as early as pre-school screening. Clinical manifestations are variable even within the same family with little phenotype/genotype correlation. Macular abnormalities are present in virtually all cases, the most typical picture being the classic spoke-wheel appearance of macular cysts. Atrophic lesions will develop in later stages. The full-field electroretinogram is critical for the diagnosis especially in case of atypical presentation or in late stages. It typically reveals an electronegative waveform in response to a standard or bright flash under scotopic conditions with a reduced b/a ratio in keeping with generalized inner retinal dysfunction. The diagnosis can be molecularly confirmed by identifying mutations in RS1. Management will include a careful refraction, low vision aids, school support and anhydrase carbonic inhibitors. Gene therapy trials are underway.