Panniculitis in dermatomyositis: A systematic review of the clinicopathologic features.

Background: Panniculitis in patients with dermatomyositis (PDMS) is rare. Objectives: Assess the clinicopathologic features described for PDMS. Methods: A systematic review of the PubMed/MEDLINE database was performed. We included cases with dermatomyositis (DMS) and confirmed panniculitis (histology/imaging). Extracted data included demographics, global region of origin, comorbidities, hallmark/nonhallmark features, muscle disease, panniculitis onset relative to classical DMS, symptomatology, physical findings, triggers, autoantibodies, extracutaneous involvement, histopathology, treatment, and prognosis. Results: Fifty-eight studies were included (91 patients). PDMS primarily occurred in relatively young women (mean age 35 years, female to male ratio 4.4:1). Adults predominated (adult:juvenile ratio 2.6:1). All had hallmark DMS features. A minority had nonhallmark findings. <1/4 reported extracutaneous involvement (pulmonary complications predominated). Cancer-associated disease was uncommon (7.4%). Panniculitis occurred before/simultaneously/after features of classical DMS. The clinical and histopathologic findings mimic lupus panniculitis, although lipoatrophy was uncommon (12.7%). A lobular/lobular predominant, lympoplasmacytic panniculitis was most common. Treatment regimens included combinations of systemic steroids/traditional steroid-sparers/Janus kinase inhibitors/biologics. The majority had a good/complete response (67.3%), but recalcitrant disease (22.4%) was reported. Limitations: Retrospective nature, inconsistent reporting of parameters, lack of longitudinal data. Conclusions: PDMS primarily occurs in females, mimics lupus panniculitis, and responds to therapy.