Genital Lichen Sclerosus - Epidemiology, Comorbidities and the Role of Vulvar and Penile Microbiome

PART A: Microbiome study The participants will be included continuously at the Dermatology clinic in connection with the regular doctor's visit. All cases included will be asked to complete Dermatology Life Quality Index (DLQI) questionnaires. A first cotton swab sample will be taken from a penile affected skin (including glans penis and coronal sulcus) in men with genital LSc before treatment and from vulvar affected skin (including mons pubis, labia minora and labia majora) in women with genital LSc before treatment. A second cotton swab sample will be taken from the same sites at week 12 after the treatment including both topical therapies and circumcision. The topical treatment will be discontinued a week prior to visit. Allowed treatment options include topical and systemic corticosteroids and topical calcineurin inhibitors (tacrolimus, pimecrolimus) for both sexes and circumcision for men. In extreme resistant cases of genital LSc in women even methotrexate, hydroxychloroquine will be recommended as systemic treatment. The samples will be analyzed using 16S ribosomal RNA metagenomic sequencing to identify the microbiome. Microbio analysis at Laboratory Medicine, Ryhov is today an established method based on "next generation sequencing" (NGS) for analysis of 16S rDNA, which has previously been used for analysis of skin and throat samples in psoriasis projects as well as intestinal biopsies and faecal samples from patients with inflammatory bowel disease. The microbial skin flora is sampled using a microbial swab (eNAT, Copan). Taxonomic classification and a determination of numbers per sample of each taxonomic unit is made on the basis of a reference database (Silva; https://www.arb-silva.de/) and suitable bioinformatics analysis tools such as QIIME2 (https://qiime2.org/) and mothur (https://mothur.org/). Group differences are examined with generalized linear models adapted for number data (eg DESeq2 and glue; https://bioconductor.org/) in the statistical programming environment R (https://cran.r-project.org/), and the analyzes are corrected based on gender and age. The biochemical properties of the microbiome are predicted using reference genomes based on the 16S composition of the samples using PICRUSt2 (https://github.com/picrust/picrust2/wiki), and examined for group differences.

PART B:

• A retrospective nationwide cohort study will be conducted using national Swedish registers (National Patient Register, Swedish Cancer Register) and LISA database (Longitudinal integration database for health insurance and labor market studies). The patients diagnosed with LSc (ICD-10 diagnosis code - L90) during 20-years period between January 1, 2001 and January 1, 2021 will be selected.
• Comorbidity will be determined.