SNP Shot: Genomic Insights

Choroideremia is an inherited disorder primarily affecting males and causing a gradual decline in vision. Initial symptoms often manifest in early childhood as difficulty seeing in low light conditions (night blindness). Subsequently, individuals experience a gradual constriction of their peripheral vision, leading to tunnel vision, and a reduction in visual acuity, making it difficult to discern fine details. These visual impairments arise from the progressive atrophy, or loss, of cells in the retina, the light-sensitive tissue at the back of the eye, and the choroid, the adjacent vascular layer. While the rate of vision deterioration varies from person to person, all individuals with choroideremia eventually experience blindness, typically by late adulthood.

Inheritance:

Choroideremia follows an X-linked recessive inheritance pattern. The CHM gene, responsible for this condition, resides on the X chromosome, one of the two sex chromosomes. Males, possessing only one X chromosome, develop the condition if they inherit just one altered copy of the CHM gene. Females, with two X chromosomes, must inherit a mutated copy of the gene on both X chromosomes to be affected. Consequently, X-linked recessive disorders are far more prevalent in males than females. A defining feature of X-linked inheritance is that fathers cannot transmit X-linked traits to their sons. In X-linked recessive inheritance, a female carrying a single mutated copy of the CHM gene on one X chromosome is considered a carrier. While she can pass the altered gene onto her offspring, she generally remains asymptomatic. However, female carriers of a CHM mutation may exhibit minor areas of retinal cell loss, detectable through comprehensive eye examinations. These subtle changes can potentially lead to vision problems later in life.