Increased histological severity and chronicity of interface inflammation in anti‐MDA5 dermatomyositis—A comparative dermatopathological analysis

Abstract

AbstractAnti‐melanoma differentiation‐associated gene 5 (MDA5) dermatomyositis is characterized by serological detection of anti‐MDA5 antibody and rapidly progressive interstitial lung disease. In this study, the largest cohort of skin biopsies to date of anti‐MDA5 dermatomyositis was reviewed and compared with cases of dermatomyositis with negative serology. Findings contribute to the histological diagnosis and evaluation of the severity of cutaneous inflammation in anti‐MDA5 dermatomyositis. Skin biopsies collected over a 7‐year period from individuals with clinically and histologically confirmed dermatomyositis with anti‐MDA5 serology were reviewed. A total of 46 cases with 17 anti‐MDA5 positive cases were retrieved. Patients with positive antibody were younger (53.7 vs. 60.6 years, p = .013). No differences in epidermal changes (p > .05) were observed. Pertaining to interface changes, anti‐MDA5 dermatomyositis showed a higher degree of pigmentary incontinence (p = .014), suggesting increased and sustained cutaneous inflammation. Periodic acid–Schiff (PAS) stain demonstrated a greater degree of basement membrane thickening (p = .045). Other parameters, including dermal inflammation, dermal mucin deposition and vasculitic/vasculopathic features did not show statistical difference between anti‐MDA5 positive and negative dermatomyositis (p > .05). Findings suggest increased cutaneous inflammation for anti‐MDA5 dermatomyositis. In skin biopsies, marked pigmentary incontinence or basement membrane thickening should raise suspicion of anti‐MDA5 dermatomyositis.