SNP Shot: Genomic Insights

Familial exudative vitreoretinopathy (FEVR) is an inherited condition that can lead to progressive vision impairment. It affects the retina, the light-sensitive tissue at the back of the eye responsible for sight. In FEVR, blood vessels fail to develop properly at the periphery of the retina, reducing blood flow to this area.

The symptoms of FEVR vary considerably, even among members of the same family. Some individuals with retinal abnormalities experience no vision problems. However, in others, the decreased blood supply can cause the retina to fold, tear, or detach from the back of the eye (retinal detachment). This damage can result in vision loss and even blindness. Other possible eye issues include misaligned eyes (strabismus) and leukocoria, a white reflection in the pupil.

Some individuals with FEVR may also experience reduced bone mineral density, making their bones weaker and increasing their susceptibility to fractures.

Inheritance:

FEVR can be inherited in different ways depending on the specific gene involved. The most common cause involves mutations in the FZD4 or LRP5 genes, which typically follow an autosomal dominant inheritance pattern. This means that only one copy of the mutated gene is needed in each cell to cause the condition. Often, individuals with autosomal dominant FEVR inherit the gene from a parent, who may or may not exhibit any symptoms of the disorder.

FEVR resulting from LRP5 gene mutations can also be inherited in an autosomal recessive manner. This requires both copies of the gene in each cell to be mutated for the condition to develop. In this case, both parents of an affected individual carry one copy of the mutated gene, but they themselves do not have FEVR.

When FEVR is caused by mutations in the NDP gene, it is inherited in an X-linked recessive pattern. The NDP gene resides on the X chromosome, one of the two sex chromosomes. Males, possessing only one X chromosome, will develop the condition if they inherit one mutated copy of the gene. Females, with two X chromosomes, would need mutations in both copies to be affected. Consequently, X-linked disorders like this one are much more common in males than in females. A defining characteristic of X-linked inheritance is that fathers cannot transmit X-linked traits to their sons.