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Can’t Diagnose That Skin Disease?

RashX is looking to provide you with more clarity on hard-to-diagnose skin diseases.

Dermatologists can now use single cell technology to diagnose even hard-to-identify skin conditions.

Precision medicine has been used in fields such as oncology for over two decades but is yet to be widely used in dermatological settings. [1] A newly published proof-of-concept study has shown that single-cell sequencing can distinguish between two common inflammatory skin diseases: atopic dermatitis (AD) and plaque psoriasis. [2] With drug therapies for these diseases targeting dysregulated pathways specific to the disease, it is key to provide a correct diagnosis, which can be challenging through clinical observations and histology.

Along with healthy control tissue, the study utilized biopsies from patients diagnosed with plaque psoriasis (eight samples) and AD (seven samples), as well as biopsies from six patients with indeterminate rashes. Having isolated cutaneous immune cells, T cells and antigen-presenting cells (APCs) were profiled with single-cell RNA sequencing (scRNA-seq) using 10X Genomics technology.

Skin-resident memory T cells (Trm) are key to the findings, with many genes newly shown to be differentially dysregulated in psoriasis and AD. “By employing a very high-resolution single-cell discovery technology, we expanded the number of known psoriasis-specific genetic abnormalities in this cell population about 10-fold,” said Dr. Jeffrey B. Cheng, co-corresponding author, Department of Dermatology, University of California, San Francisco.

“Interestingly, many of the genes that have been reported as related to psoriatic disease are also abnormal in many other inflammatory skin diseases,” said Dr. Cheng. But now with the identification of these psoriasis-specific genetic abnormalities, the 10X Genomics scRNA-seq technology can be used to distinguish between psoriasis and AD, even in difficult to diagnose cases.

In addition to the diagnostic benefits, the genetic abnormalities found to be unique to psoriasis can be utilized as new drug targets. This would expand available treatment options while potentially reducing the risk of impacting unrelated cells and pathways of the immune system. The authors note that “~20 to 50% of patients still do not achieve substantial improvement on a given drug,” emphasizing the need for additional drug targets. [2]

To facilitate diagnostic potential, the authors launched an online resource, RashX, where invited researchers can submit the molecular profile of indeterminate rash samples to identify psoriasis-like or AD-like abnormalities. RashX is currently based on the same 10X Genomics scRNA-seq technology used in the study, which requires institutions to have the correct expertise, funding, and equipment to utilize the tool. However, the authors are looking to expand accessibility through alternative profiling approaches, such as immunofluorescence technology.

Paralleling the single cell RNA-sequencing research that enabled development of the RashX Precision Medicine platform, Dr. Cheng was selected as a 2021 National Psoriasis Foundation Discovery Grant awardee. This proof-of-concept research award aims to “use new single cell profiling approaches, with an emphasis on highly multiplexed immunofluorescence to improve classification, provide insight into molecular drivers, and identify biomarkers for treatment responsiveness of psoriatic subtypes,” explained Dr. Cheng.

With regard to the future directions of their research, “We anticipate expanding this approach to create a standardized framework to place rashes in the context of large existing datasets,” Dr. Cheng said, “to link an individual rash’s molecular features to disease prognosis and drug response based on contributions from clinical centers worldwide.”

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1.       The Lancet. 20 years of precision medicine in oncology. Lancet. 2021;397(10287):1781. doi:10.1016/S0140-6736(21)01099-0

2.       Liu Y, Wang H, Taylor M, et al. Classification of human chronic inflammatory skin disease based on single-cell immune profiling. Sci Immunol. 2022;7(70):eabl9165. doi:10.1126/sciimmunol.abl9165

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