Did you know that August is Psoriasis Awareness Month? In celebration of this, we are shining a light on the complex relationship between the microbiome and psoriasis, with the help of a review by Dr. Daniel Lewis.
In scientific terms, psoriasis is a chronic inflammatory disorder characterized by keratinocyte hyper-proliferation and thickening of the stratum corneum.
In simpler terms, it is a skin condition that causes red, flaky or crusty patches of skin – some describe it has having your skin covered with silvery scales. While most people are affected with small patches, this can vary. As it is a long-lasting condition, those affected by psoriasis may also suffer from flare-ups – periods where a person shows no symptoms or severe ones.
The research of Dr. Daniel Lewis and team aimed to characterize the microorganisms associated with psoriasis. To do this, they examined the results of major associations’ studies and possible mechanisms of pathogenesis. Two different authors searched both science journals, Medline and Scorupus, using terms related to psoriasis. When examining the various studies, they identified there were changes in the levels of microorganisms in the presence of psoriasis. The bacteria involved were numerous. This included higher rates of Streptococcus found in psoriatic lesions when compared with normal skin. Staphylococcus may also play a role in the formation of psoriatic lesions with 60% of isolates excreting staphylococcal enterotoxins. Found out more about Staphylococci in our blog post by Dr. Egert.
Cutibacterium decreases in the presence of psoriasis and this suggests lower levels of this microorganism may impair the skin protective barrier function. In another study, Malassezia count went down in patients with scalp psoriasis and when they received oral ketoconazole they also showed clinical improvements. If you want to know more about the relationship between Malassezia and the microbiome, we wrote about it here.
It was also found that the pathogenesis of psoriasis may involve a breakdown of immune tolerance to cutaneous microorganisms, that is, bacteria that affects the skin.
In conclusion, it remains unclear if changes in the composition of the microbiome have a casual association with psoriasis or are simply a consequence of the inflammatory microenvironment. Techniques enabling strain-level analysis rather than species-level analysis of the skin microbiome are likely necessary to determine microbial signatures of psoriasis. The next steps here are about furthering this research and channeling this into actionable insight. For now, for this year’s Psoriasis Awareness Month, we will continue to raise awareness and celebrate the increasing scientific understanding.
 Lewis, 2019 Mechanisms of microbial pathogenesis and the role of the skin microbiome in psoriasis: A review, p.161
 Tomi NS, Kranke B, Aberer E. Staphylococcal toxins in patients with psoriasis, atopic dermatitis, and erythroderma, and in healthy control subjects. J Am Acad Dermatol 2005;53:67-72.
 Farr PM, Krause LB, Marks JM, et al. Response of scalp psoriasis to oral ketoconazole. Lancet 1985;2:921-922