Abstract: Objective: To detect the mutation of KRT9 gene in two epidermolytic palmoplantar keratosis families. Methods: Clinical data of each family were collected. DNA was extracted from the peripheral blood of patients, normal people in two family and 200 healthy volunteers. All exons of KRT9 gene were amplified by polymerase chain reaction (PCR) and the product was performed by sanger sequencing. Results: A missense mutation c.487C>T (p.163R>W) was identified in exon 1 of KRT9 gene in all patients of both families. This missense mutation was not found in healthy family members and 200 normal controls. In family one, the daughter and grandfather not only manifested hyperkeratosis of the palmoplantar skins, but congenital knuckle pads and congenital flexion deformity, while all the patients in another family did not have this symptom. Conclusion: The missense mutation of 487C > T of the KRT9 gene is the genetic cause of these two families with epidermolytic palmoplantar keratosis. Clinical phenotypes caused by the same mutation among individual from different family or same family may be different.

Key words: epidermolytic palmoplantar keratosis families, KRT9, clinical manifestation