Recognizing PSO-HS as a Distinct Subset with Shared Genetic Risk

A recent multicenter study published in Journal of the American Academy of Dermatology in June 2025 characterizes patients with coexisting psoriasis (PSO) and hidradenitis suppurativa (HS), termed PSO-SH, as a clinically distinct subset, emphasizing the importance of its recognition to improving patient management.

Here’s a quick look at the study and what it found.

Clinical Characteristics and Comorbidity Burden
Drawing from the US-based All of Us research initiative and international dermatology referral centers, the authors identified 87 PSO-SH patients and compared them to PSO-only and HS-only cohorts.

Nearly 90 percent of PSO-SH patients had at least 1 comorbidity, with obesity being particularly prevalent. The risk of Crohn’s disease was significantly elevated, ranging from 4.6 to 11.9 times higher than in the comparator groups. Patients with PSO-SH also reported significantly lower physical and social health scores compared to those with PSO alone.

Genetic Susceptibility and Shared Pathways
Genetic analysis using a psoriasis-specific polygenic risk score (PRS) based on 88 loci revealed that PSO-SH patients carried the highest cumulative genetic risk. The investigators examined both human leukocyte antigen (HLA) and non-HLA regions, and found that genetic susceptibility overlapped between PSO and HS at non-HLA loci.

Notably, HS-only patients also demonstrated elevated PSO-PRS compared to healthy controls, reinforcing the presence of shared immunopathogenic pathways. In contrast, HLA-associated risk was primarily observed in PSO and PSO-SH patients, suggesting that HLA-linked susceptibility is specific to PSO.

Higher non-HLA PRS scores were associated with earlier onset of psoriasis and improved response to TNF-α inhibitors in PSO. Clinically, PSO-SH presented with features distinct from HS-only and PSO-only cohorts. HS typically preceded the onset of psoriasis by several years, and nearly half of patients exhibited HS involvement beyond intertriginous sites. Most had moderate-to-severe HS (Hurley stage II or III), and although joint pain was reported by over a third (36.5%), psoriatic arthritis was confirmed in only 13.5%, distinguishing PSO-SH from syndromic variants such as PsAPASH.

Limitations and Implications for Care
The study’s limitations include the retrospective collection of some clinical data, limited information on PSO severity, and a relatively small number of genome-sequenced patients. Nonetheless, all diagnoses were confirmed by board-certified dermatologists, and the integration of clinical registry data with deep phenotyping strengthens the overall conclusions.

Taken together, this study establishes PSO-SH as a distinct patient group with an increased risk of Crohn’s disease and high morbidity, and highlights the shared genetic susceptibility of HS and PSO at non-HLA loci. Accordingly, the shared genetic susceptibility supports consideration of therapeutic strategies developed for PSO in the management of HS.

Reference
Wiala A, Elhage KG, Leung A, et al. Patients with PSOriasis and Suppurative Hidradenitis (PSO-SH) share genetic risk factors and are at risk of increased morbidity. J Am Acad Dermatol. 2025;92(6):1303-1311. doi:10.1016/j.jaad.2025.02.015