Families

Prevalence
The SLC9A7-related variant (p.L515F) is very rare. It has been reported in two unrelated families with multigenerational non-syndromic intellectual disability.

Clinical characteristics
Male individuals with the SLC9A7-related variant (p.L515F) are characterized by moderate to severe intellectual disability, motor and speech delay, decreased muscle tone (hypotonia), proximal muscle weakness, variable deep tendon reflexes, and a finger - usually the little (pinky) finger - that curves to one side (bilateral clinodactyly).

Inheritance
Since the SLC9A7gene is located on the X chromosome (position Xp11.3), SLC9A7-related conditions are known as X-linked conditions. As males have only one X chromosome, those possessing the defective variant SLC9A7p.L515F are invariably affected. Females who are genetic carriers of the condition will have one X chromosome with a SLC9A7variant, while the other X chromosome will contain a functional copy of the gene. Hence, female carriers may not show any signs or symptoms of the condition. When a female who is carrying the defective variant SLC9A7 p.L515F variant has children and the variant is passed on to her children, then a male child will have a SLC9A7-related condition.