AUTHOR=Tochigi Mei , Takamiya Yuko , Morita Megumi , Anzawa Kazushi , Shimizu Akira , Togi Sumihito , Ura Hiroki , Niida Yo 
  
TITLE=Case Report: A case with Xeroderma pigmentosum type F manifested a mild phenotype due to a deep intronic variant of the ERCC4 gene
  
JOURNAL=Journal of Cutaneous Immunology and Allergy
  
VOLUME=Volume 9 - 2026
  
YEAR=2026
  
URL=https://www.frontierspartnerships.org/journals/journal-of-cutaneous-immunology-and-allergy/articles/10.3389/jcia.2026.16180
  
DOI=10.3389/jcia.2026.16180
  
ISSN=2574-4593
  
ABSTRACT=Xeroderma pigmentosum (XP) is a disorder that causes sun sensitivity, pigmented spots in sun-exposed areas, and neurological symptoms due to an inborn error in the DNA repair process for damage caused by sun exposure. We report a case with XP type F (XPF) diagnosed in a patient in her 70s. We identified that she was homozygous for a deep intronic variant of ERCC4, NC_000016.10(NM_005236.3): c.207+196T>A. This variant causes aberrant mRNA splicing, which confirmed the diagnosis of XP. Seven cases with the same intronic variant have been reported in Japan. In our case, we independently analyzed the qualitative and quantitative aspects of abnormal mRNA splicing, which had not been reported previously, and found approximately 7.7% of the mRNA retained normal splicing. Furthermore, immunostaining of patient’s skin with anti-ERCC4/XP antibody confirmed that the ERCC4 protein was partially expressed rather than being completely absent. This partial expression was predicted to be associated with the relatively mild phenotype observed in our patient.