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The following is a summary of “Comparative Whole Metagenome Analysis in Lesional and Nonlesional Scalp Areas of Patients with Psoriasis Capitis and Healthy Individuals,” published in the March 2025 issue of Journal of Investigative Dermatology by Pessemier et al. 

Psoriasis capitis, a common immune-mediated disorder, remains challenging to treat due to the restricted effectiveness of current therapies.  

Researchers conducted a retrospective study to analyze the whole-metagenome of the scalp microbiome in psoriasis capitis and identify metagenomic biomarkers, including taxonomic, functional, virulence factors (VF), and antimicrobial resistance genes, that might have contributed to its development.  

They collected scalp samples from 83 healthy individuals (top and back scalp) and 64 lesional and nonlesional sites from individuals with untreated psoriasis capitis. The qPCR targeting the 16S and 18S ribosomal RNA (rRNA) genes measured microbial load. Metagenomic analysis identified taxonomic and functional microbial changes.  

The results showed a significant reduction in microbial load in psoriatic scalp regions compared to nonlesional areas. Metagenomic analysis identified lower levels of  Cutibacterium species (C. modestum, C. namnetense, C. granulosum, C. porci) and increased Staphylococcus aureus in lesions. A higher presence of efflux pump protein–encoding genes suggested antimicrobial resistance (AMR) mechanisms, potentially targeting human antimicrobial peptides (AMP) like cathelicidin LL-37 (commonly found in psoriasis lesions).  

Investigators concluded the changes in the scalp microbiome, characterized by reduced Cutibacterium species and increased Staphylococcus aureus, along with potential AMR, played a role in the development of psoriasis capitis. 

Source: jidonline.org/article/S0022-202X(24)01984-5/fulltext