Increased MxA protein expression and dendritic cells in spongiotic dermatitis differentiates dermatomyositis from eczema in a single-center case-control study

Abstract

Background: Dermatomyositis (DM) is conventionally characterized by interface dermatitis (ID) on skin histopathology. A subset of DM patients has skin biopsies showing spongiotic dermatitis (SD), a histopathology more commonly seen in eczema. In this study, we aimed to (a) identify the percentage of clinically diagnosed DM patients with SD skin biopsies, (b) identify cytokine and cell markers that can help determine if a SD skin biopsy is consistent with DM.

Methods: In this case-control study, biopsy specimens from ten DM patients with SD (DM-SD) were compared to specimens from ten healthy controls, ten patients with eczema, and 12 patients with DM with ID (DM-ID). Specimens were stained by immunohistochemistry for MxA, IFN-β, CD11c, and BDCA2. One-way ANOVA with Bonferroni's multiple comparison test was used to compare protein expression between groups.

Results: Eleven 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, and BDCA2 protein expression was significantly higher in DM-SD compared to eczema and healthy controls. Expressions of MxA, IFN-β, and BDCA2 were not significantly different between DM-SD and DM-ID.

Conclusion: Increased MxA, IFN-β, CD11c, and BDCA2 protein expression may aid in distinguishing between DM-SD and eczema and warrants further investigation.

Keywords: IFN-β; MxA; dendritic cells; dermatomyositis; interface dermatitis; spongiotic dermatitis.

Figure 1.

Clinical images of patient 10 (see table 2) with classic dermatomyositis and histopathologic spongiotic dermatitis. a) Göttron papules on fingers and mechanics hands, b) Göttron papules on elbows.

Figure 2.

Representative H&E stain in skin of (a) healthy controls, and lesional skin of patients with (b) eczema, (c) dermatomyositis with spongiotic dermatitis (DM-SD) histopathology, and (d) dermatomyositis with interface dermatitis (DM-ID) histopathology. Immunohistochemical protein expression of MxA in skin of (e) healthy controls, and lesional skin of (f) eczema patients, (g) DM-SD patients, and (h) DM-ID patients. Immunohistochemical protein expression of IFN-β in skin of (i) healthy controls, and lesional skin of (j) eczema patients, (k) DM-SD patients, and (l) DM-ID patients. All images at 200X total magnification.

Figure 3.

MxA (a) area percent and (b) mean fluorescence intensity and IFN-β (c) area percent and (d) mean fluorescence intensity were evaluated: n= 10 for healthy controls, eczema and dermatomyositis with spongiotic dermatitis (DM-SD); n=12 for dermatomyositis with interface dermatitis (DM-ID). IFN-β: interferon beta, MxA: human myxovirus resistance protein 1. Area and intensity values represent both epidermis and dermis. Data are displayed as group mean ± SEM. **p< 0.01, ***p<0.001, and “ns” indicates p>0.05.

Figure 4.

Immunohistochemical protein expression of CD11c in skin of (a) healthy controls, and lesional skin of patients with (b) eczema, (c) dermatomyositis with spongiotic dermatitis (DM-SD), and (d) dermatomyositis with interface dermatitis (DM-ID). Immunohistochemical protein expression of BDCA2 in skin of (e) healthy controls, and lesional skin of patients with (f) eczema, (g) DM-SD, and (h) DM-ID. H&E staining for identification of eosinophils in (i) healthy controls, and lesional skin of patients with (j) eczema, (k) DM-SD, and (l) DM-ID. (m) CD11c, (n) BDCA2, and (o) eosinophil cell counts/HPF were quantified: n= 10 for healthy controls, eczema, and DM-SD; n=12 for DM-ID. HPF: high power field. Eosinophils on H&E at 400X total magnification. All other images at 200X total magnification. Data are displayed as group mean ± SEM. *p<0.05, **p< 0.01, ***p<0.001, and “ns” indicates p>0.05.

Figure 5.

Mucin stain in skin of (a) healthy controls, and lesional skin of patients with (b) eczema, (c) dermatomyositis with spongiotic dermatitis (DM-SD), and (d) dermatomyositis with interface dermatitis (DM-ID). Mucin (e) area percent and (f) mean fluorescence intensity were evaluated: n= 10 for healthy controls, eczema, and DM-SD; n=12 for DM-ID. Hale staining; mucin represented in blue, collagen represented in red. All images at 100X total magnification. Data are displayed as group mean ± SEM. ***p< 0.001 and “ns” indicates p>0.05.