Genome-Wide Association Study Identifies Genes for Hair Growth and Patterning are Associated With Pilonidal Disease

BACKGROUND: Pilonidal sinus disease is a highly morbid condition characterized by the formation of chronic sinus tracts throughout the sacrococcygeal region. Despite its commonality and strong association with family history, there is no prior investigation of genetic risk factors for pilonidal sinus disease.

OBJECTIVE: To identify genetic risk factors for pilonidal sinus disease.

DESIGN: Genome-wide association study.

SETTINGS: The United Kingdom Biobank, FinnGen Biobank, and PennMedicine Biobank.

PATIENTS: There were 772,072 participants.

MAIN OUTCOME MEASURE: Genome-wide significant variants (p < 5x10 -8) were mapped to genes using physical distance and gene expression in skin. Genetic correlation between pilonidal sinus disease and morphometric, androgen-driven, and hair phenotypes was estimated with LD score regression. Finally, a genome-first approach to rare, predicted deleterious variants in hair shaft genes TCHH, PADI3, and TGM3 was conducted for association with pilonidal sinus disease via PennMedicine Biobank.

RESULTS: Genome-wide association study comprised of 2,835 individuals with pilonidal sinus disease identified 5 genome-wide significant loci, prioritizing HDAC9, TBX15, WARS2, RP11-293M10.1, PRKAR1B, TWIST1, GPATCH2L, NEK9, and EIF2B2, as putative causal genes; several of these genes have known roles in balding and hair patterning. There was significant correlation between the genetic background of pilonidal sinus disease and that of the androgen-driven hair traits male pattern baldness and young age at first facial hair. In a candidate analysis of genes associated with syndromic hair disorders, rare coding variants in TCHH, a monogenic cause of uncombable hair syndrome, were associated with increased prevalence of pilonidal sinus disease (OR 4.81 [5% CI, 2.06-11.2]).

LIMITATIONS: This study is limited to European ancestry. However, because there is a higher incidence of pilonidal sinus disease in men of European ancestry, this analysis is focused on the at-risk population.

CONCLUSION: Genetic analysis of pilonidal sinus disease identified shared genetic architecture with hair biology and androgen-driven traits. As the first study investigating the genetic basis of pilonidal sinus disease, this provides biological insight into the long-appreciated connection between the disease state, male gender, and hair. See Video abstract.