Shared Genetic Architecture of Multiple Sclerosis and Psoriasis: Evidence for IL-17 and JAK–STAT Pathway Involvement
Multiple sclerosis and psoriasis are clinically distinct diseases, yet both are driven by immune dysregulation and T-cell-mediated inflammation. Multiple sclerosis primarily damages central nervous system myelin, whereas psoriasis produces chronic inflammatory plaques in the skin; however, both conditions involve overlapping immune pathways, including IL-17, TNF, and interferon signaling. The article addresses an important clinical paradox: therapies effective in one disease may worsen the other, as reported for TNF inhibitors in multiple sclerosis and interferon-β in psoriasis. This makes the shared biology of these diseases highly RELevant for precision medicine.
Study Design: Epidemiology Integrated With Human Genetics
Patrick and colleagues used a multi-layered design combining epidemiological analysis, trans-disease genetic meta-analysis, colocalization, pathway analysis, and Mendelian randomization. The epidemiological component drew on Optum Clinformatics medical claims data from more than 30 million individuals, including 141,544 patients with multiple sclerosis, 742,919 with psoriasis, and 4,637 with both diseases. The genetic component used genome-wide association study summary statistics from psoriasis and multiple sclerosis cohorts, allowing the authors to ask whether the two disorders share risk loci beyond the major histocompatibility complex.
Epidemiological Evidence for Comorbidity
The claims-based analysis showed that psoriasis was associated with a modest but statistically significant increase in multiple sclerosis risk after adjustment for demographic and clinical covariates. In the fully adjusted model, psoriasis was associated with multiple sclerosis with an odds ratio of 1.07, while multiple sclerosis was associated with psoriasis with an odds ratio of 1.10. Both diseases were also associated with several overlapping clinical factors, including vitamin D deficiency, smoking, asthma, diabetes, inflammatory bowel disease, rheumatoid arthritis, coronary artery disease, and morbid obesity. These findings support the concept that psoriasis and multiple sclerosis do not meRELy coexist by chance, but may arise in part from shared systemic inflammatory mechanisms.
Genetic Architecture: Shared and Opposing Risk Loci
The trans-disease meta-analysis identified more than 20 genetic loci outside the major histocompatibility complex that were associated with both diseases. Importantly, some loci showed the same direction of effect in psoriasis and multiple sclerosis, whereas others showed opposing effects. This mixture of concordant and discordant genetic architecture is biologically informative: it suggests that the two diseases share immune regulatory pathways, but that specific variants may push those pathways toward different pathological outcomes depending on tissue context, cellular state, or downstream signaling balance. Notable loci implicated genes such as IL12B, TNFAIP3, TYK2, TNFRSF1A, STAT3, STAT5A/B, SOCS1, REL, and RUNX3.
Functional Interpretation: IL-17, TNF, and JAK–STAT Pathways
The most mechanistically important result is the convergence of shared genetic loci onto immune signaling pathways already known to be central in inflammatory disease. Co-expression and pathway enrichment analyses identified clusters enriched for IL-17 signaling, TNFα signaling, JAK–STAT signaling, IL-12 signaling, and IL-6–JAK–STAT3 signaling. One cluster containing CSF2 and TNFAIP3 was enriched for IL-17 signaling, another containing IL12B and TYK2 was enriched for JAK–STAT signaling, and a third containing CAMK2G and TNFRSF1A was enriched for necroptosis. These findings place the psoriasis–multiple sclerosis RELationship within a coherent immunological framework involving Th17 biology, cytokine transduction, and inflammatory cell survival pathways.
Mendelian Randomization: Evidence for Directionality
To move beyond association, the authors applied six Mendelian randomization methods. Psoriasis showed evidence of a causal effect on multiple sclerosis in four of six methods, while the remaining two methods were nominally significant. In contrast, the analysis did not support a significant causal effect of multiple sclerosis on psoriasis. Multivariable Mendelian randomization further showed that the psoriasis-to-multiple-sclerosis effect remained significant after conditioning on type 1 diabetes, type 2 diabetes, inflammatory bowel disease, vitamin D level, body mass index, and alcohol-RELated traits. This strengthens the interpretation that psoriasis itself, or its underlying genetic liability, contributes to multiple sclerosis risk independently of several measured comorbidities.
Clinical and Translational Implications
The study has important implications for risk stratification and therapeutic development. It suggests that clinicians should be attentive to neurological symptoms in patients with psoriasis, particularly in those with additional immune-mediated comorbidities or risk factors. At the same time, the presence of opposing genetic effects cautions against assuming that all anti-inflammatory interventions will behave similarly across diseases. The findings help explain why some immune pathways, such as TNF or interferon signaling, may have disease-specific therapeutic consequences. Overall, the article advances a precision-medicine view in which psoriasis and multiple sclerosis are connected through shared but complex immune-genetic networks, especially IL-17/TNFα and JAK–STAT signaling.
Disclaimer: This blog post is based on the provided research article and is intended for informational purposes only. It is not intended to provide medical advice. Please consult with a healthcare professional for any health concerns.
References:
Patrick, M. T., Nair, R. P., He, K., Stuart, P. E., Billi, A. C., Zhou, X., ... & Tsoi, L. C. (2023). Shared genetic risk factors for multiple sclerosis/psoriasis suggest involvement of interleukin‐17 and Janus Kinase–signal transducers and activators of transcription signaling. Annals of neurology, 94(2), 384-397.
