Do histopathological features correlate with systemic manifestations in dermatomyositis? Analysis of 42 skin biopsy specimens from 22 patients

Background: Understanding whether specific histopathologic features on skin biopsy are predictive of systemic associations in dermatomyositis (DM) would be useful to guide clinical screening. Methods: Through retrospective medical record search, clinical and laboratory findings of patients with DM were documented. Existing skin biopsy slides were re-reviewed blindly. Results: Of all biopsy specimens (n = 42), the most frequent histopathological finding was vacuolar interface dermatitis (95%). Other features included perivascular lymphocytic infiltrate (71%), increased dermal mucin (40%), vessel wall thickening (12%), follicular plugging (9.5%), and dermal sclerosis (7%). Neutrophilic infiltrate was observed in three biopsies from a patient with adalimumab-associated DM. Vasculitis was not observed. There was no statistically significant difference in the presence of any histopathological feature and that of various systemic manifestations (i.e., myopathy, interstitial lung disease [ILD] and malignancy). However, we observed that dense lichenoid infiltrate rather than pauci-inflammatory changes correlated with severe itching (p < 0.001). Patients with MDA-5 antibodies were significantly more likely to have vasculopathy than those without (p = 0.029*). Conclusions: No dermatopathologic feature was reliably predictive of myopathy, ILD, or malignancy. This finding implies that, regardless of histopathologic findings, patients should be screened for associated conditions as clinically indicated.