Clinical factors associated with cutaneous histopathologic findings in dermatomyositis

Background Common histopathologic findings in cutaneous dermatomyositis include vacuolar interface with dyskeratosis, mucin, and perivascular inflammation. Data examining the relationships between these and other histologic abnormalities, or their dependence on biopsy site, and medications are limited. Methods Using 228 dermatomyositis skin biopsies and statistical analyses including Chi‐squared analyses, calculations of relative risk, and adjusted generalized estimating equation regressions, we investigated relationships between 14 histopathologic findings and the impact of clinical factors on these findings. Results In biopsies taken from sites of visible rash, interface dermatitis was seen in 91%, and 95% had at least one of perivascular inflammation, mucin, or basal vacuolization. Vascular abnormalities were not closely associated with epidermal or inflammatory findings. Concomitant prednisone significantly decreased the odds of basal vacuolization (odds ratio [OR] = 0.34, 95% confidence interval [CI]: 0.12‐0.98, P‐value = 0.05), perivascular inflammation (OR = 0.19, 95% CI: 0.07‐0.53, P‐value = 0.002), and vessel damage (OR = 0.81, 95% CI: 0.68‐0.96, P‐value = 0.02). Conclusion Vasculopathy and classic findings of interface dermatitis may be driven by unique pathways in dermatomyositis. Corticosteroid use may impact skin biopsy findings. There is a need for clinicopathologic correlation when diagnosing dermatomyositis.