X-linked infantile nystagmus is a condition characterized by abnormal eye movements. Nystagmus is a term that refers to involuntary side-to-side, up-and-down, or circular movements of the eyes. In people with X-linked infantile nystagmus, the movements are typically side-to-side. In individuals with this condition, nystagmus is present at birth or develops within the first six months of life.

Variants (also called mutations) in the FRMD7 gene cause X-linked infantile nystagmus. The FRMD7 gene provides instructions for making a protein whose exact function is unknown. This protein is found mostly in areas of the brain that control eye movement and in the light-sensitive tissue at the back of the eye (retina). Research suggests that FRMD7 gene variants cause nystagmus by disrupting the development of certain nerve cells in the brain and retina.

The incidence of X-linked infantile nystagmus is estimated to be 4.4 in 10,000 individuals.

X-linked infantile nystagmus is inherited in an X-linked pattern.  The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes.  In males (who have one X chromosome), a variant in the only copy of the gene in each cell is sufficient to cause the condition. In females (who have two copies of the X chromosome), one altered copy of the gene can cause the condition, although the features may be less severe than in individuals with two altered copies. Some of these individuals may have no signs or symptoms at all; approximately half of females with only one altered copy of the FRMD7 gene have no symptoms of this condition.

Published Date: September 01, 2023
Published By: National Institutes of Health