The intestinal and immune disorder trichohepatoenteric syndrome (THES) is characterized by mutations in human Ski2 and Ski3, also known as SKIV2L and TTC37, respectively. The mechanism by which these mutations leads to the immunodeficiency, chronic diarrhea, failure to thrive and liver disease associated with THES is unknown. To what degree THES patient mutations in Ski2 affect Ski2 function and how the differences in Ski2 function could lead to varying patient outcomes has not been studied. Here, we assayed function of THES ski2 mutants in the yeast homolog. Our results show that most THES patient mutations cause severe dysfunction in Ski2. This provides the first functional analysis of these mutations and suggests that the yeast assay may be helpful in distinguishing between pathological and benign variants.