Eosinophilic Cellulitis Pathogenesis May Involve JAK1/JAK2-STAT5 Pathways

Doug Brunk

June 26, 2023


Eosinophilic cellulitis (EC) is a type 2 inflammatory disease that activates the JAK1/JAK2-STAT5 pathways, an analysis of skin biopsy specimens suggests.


  • To better understand the pathogenesis of EC, also called Wells syndrome, French researchers analyzed archival skin biopsy samples from 14 patients with EC and eight healthy controls.

  • Assessment of samples in the case series was conducted between 2020 and 2022 and included histology, Janus kinase (JAK)–signal transducer and activator of transcription (STAT) immunohistochemistry, and gene profiling.

  • The mean age of the patients and healthy controls was 50 years.


  • The researchers observed pronounced type 2 inflammation in the EC lesions, characterized by several markers, including chemokines CCL17, CCL18, and CCL26 and interleukin 13.

  • They also observed preferential activation of the JAK1/JAK2–STAT5 pathways in the lesions.

  • In one index patient with EC that was refractory to treatment with methotrexate, oral prednisone, and other therapies, complete clinical remission of skin lesions was observed after 1 month of treatment with the JAK inhibitor baricitinib. (No other patients were treated.)


  • While the results need to be replicated, the researchers conclude that the findings are "promising" and "advocate for the development of JAK1/JAK2 targeting treatment approaches in EC and other eosinophilic diseases."


  • Axel P. Villani, MD, PhD, of the University of Lyon, France, led the research. The study was published online June 21, 2023, in JAMA Dermatology.


  • Response to baricitinib therapy was observed in only one patient with EC; replication in other patients is required.


  • Villani reported receiving consulting fees from AbbVie, Almirall, Amgen, Bristol-Myers Squibb, Eli Lilly, Janssen, LEO Pharma, MSD, Novartis, and UCB outside the submitted work. Many of the co-authors reported having received funding and other support from several pharmaceutical companies. No information on funding for the study was provided.

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