Increased MxA Protein Expression and Dendritic Cells in Spongiotic Dermatitis Differentiates Dermatomyositis from Eczema

Majid Zeidi¹, Kristen Chen ¹, Basil Patel ², Rachel Lim ³ and Victoria Werth ¹, ¹Corporal Michael J. Crescenz VAMC, Philadelphia, PA, USA and Department of Dermatology, University of Pennsylvania, Philadelphia, PA, USA, Philadelphia, PA, ²Department of Dermatology, University of Pennsylvania, Philadelphia, PA, USA, Philadelphia, PA, ³Corporal Michael J. Crescenz VAMC, Philadelphia, PA, USA, Philadelphia

Meeting: 2019 ACR/ARP Annual Meeting

Keywords: dendritic cells and Autoimmune Skin Disease, dermatomyositis, inflammatory cytokines, interferons

Session Information

Date: Monday, November 11, 2019

Title: Muscle Biology, Myositis & Myopathies Poster II

Session Type: Poster Session (Monday)

Session Time: 9:00AM-11:00AM

Background/Purpose: Dermatomyositis (DM) is conventionally characterized by interface dermatitis (ID) on skin histopathology. A subset of patients with clinically diagnosed DM have skin biopsies showing spongiotic dermatitis (SD), a histopathology more commonly seen in eczema. Diagnosis of DM is challenging, with significant delays following initial presentation. Our goals were as follows: 1) to identify the percentage of clinically diagnosed DM patients with skin biopsies showing SD, 2) to identify cytokine and cell markers that can determine if a skin biopsy showing SD is consistent with DM in a patient with clinical DM.

Methods: Biopsies from 10 DM patients with SD histopathology (DM-SD) were compared to biopsies from 10 healthy controls, 10 patients with eczema, and 12 DM patients with ID histopathology (DM-ID). Skin biopsies were stained by H&E and by immunohistochemistry for MxA, IFN-β, CD11c (mDC), and BDCA2 (pDC). Mucin expression was assessed using Hale’s iron colloidal stain. Cytokines and mucin were quantified as area percent and mean intensity. Cells were quantified as mean number of cells per high power field. Fisher’s exact test was used to compare baseline patient characteristics. One-way ANOVA with Bonferroni’s multiple comparison test was used to compare protein expression between groups.

Results: 11 of 164 (6.7%) patients with a clinical diagnosis of DM at our tertiary care center were identified as having SD. MxA, IFN-β, CD11c (mDC), and BDCA2 (pDC) protein expression was significantly higher in DM-SD compared to eczema (p < 0.01) and healthy controls (p < 0.0001) (Fig. 1, 2). Expression of MxA, IFN-β, and BDCA2 were not significantly different between DM-SD and DM-ID (Fig. 1, 2). Eosinophils identified on H&E were not significantly different between DM-SD and eczema patients, although both were significantly higher compared to healthy controls and DM-ID (p < 0.01) (Fig. 2). Mucin was not significantly different between eczema, DM-SD, and DM-ID, although all were significantly elevated compared to healthy controls (p < 0.0001).

Conclusion: MxA, IFN-β, CD11c (mDC), and BDCA2 (pDC) protein expression were significantly higher in DM-SD compared to eczema skin lesions. These markers can therefore be helpful to distinguish between DM-SD versus eczema.

Figure 1. Comparison of skin biopsies from healthy controls, and patients with eczema, DM-SD, and DM-ID. a- H&E stain; b- MxA immunohistochemical protein expression; and c- IFN-b immunohistochemical protein expression. Note: All images at 10x objective magnification. Area and intensity values represent both epidermis and dermis. Data are displayed as group mean ± SEM.

Figure 2. Comparison of cell types in skin biopsies from healthy controls, and patients with eczema, DM-SD, and DM-ID. a- CD11c immunohistochemical protein expression; b- BDCA2 immunohistochemical protein expression; c- Eosinophils on H&E 40x stain. Note: All other images at 10x objective magnification. CD11c is a marker for myeloid dendritic cells and BDCA2 is a marker for plasmacytoid dendritic cells. Data are displayed as group mean ± SEM.

Disclosure: M. Zeidi, None; K. Chen, None; B. Patel, None; R. Lim, None; V. Werth, Biogen, 2, 5, Corbus Pharmaceuticals, 2, 9, University of Pennsylvania, 9.

To cite this abstract in AMA style:

Zeidi M, Chen K, Patel B, Lim R, Werth V. Increased MxA Protein Expression and Dendritic Cells in Spongiotic Dermatitis Differentiates Dermatomyositis from Eczema [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/increased-mxa-protein-expression-and-dendritic-cells-in-spongiotic-dermatitis-differentiates-dermatomyositis-from-eczema/. Accessed .

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