Parents

The KCNN2 gene encodes the SK2 channel, a protein that functions as a pore in a cell membrane and permits the selective passage of potassium ions. SK2 is mainly expressed in certain cells of the brain (neurons) where it contributes to cognition, memory and movement.

Clinical features
Patients with a genetic variants in the KCNN2 gene have variable manifestations, some of which appear early on (delays in acquiring developmental milestones such as language and walking) and other which are revealed later on during childhood or adolescence. These symptoms include, intellectual disability, autism, and abnormal involuntary movement, coordination or balance.

Prevalence
KCNN2-disorder is likely very rare, with less than 20 individuals described so far worldwide but it is possible that this disorder is underdiagnosed because of its clinical variability.

Inheritance
KCNN2-related disorders follow autosomal dominant inheritance. Mutations causing severe sporadic disorders usually occur de novo while mutations associated with milder phenotypes can be inherited from affected parents, or be transmitted over several generations
Mutations in KCNN2 are inherited in an autosomal dominant manner, with each affected individual having a 50% risk of transmitting it to his/her children. However, most mutations occur de novo and affected individuals are very often sporadic cases, i.e. a single occurrence in a family. When the mutation is de novo in a child, the recurrence risk for future pregnancies in the family is considered low (possibly <1%).