Different mutations in the PUM1 gene have been described. Some individuals with PADDAS are missing the entire PUM1 gene because a piece of their chromosome was deleted.
The underlying pathophysiology of PUM1-related disorders is still being researched. PUM1 is an RNA-binding protein that controls the expression of hundreds of mRNA targets in the brain. These targets become deregulated when there is insufficient PUM1 function, meaning that some proteins get expressed at levels that are too high.