 Most cases are caused by mutations in the EDA gene, which are inherited in an X-linked recessive pattern, called x-linked hypohidrotic ectodermal dysplasia (XLHED).A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes.In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition.