Diffuse Soft-Tissue Swelling in Antinuclear Matrix Protein-2 Antibody-Associated Dermatomyositis Sine Dermatitis

A 66-year-old man presented with progressive weakness and myalgia for 3 months, followed by anasarca and dysphagia. Physical examination showed symmetric limb-girdle weakness and generalized edema without skin rashes. Creatine kinase was 1584 U/L (normal: <308). Muscle biopsy displayed inflammatory myopathy with perifascicular pathology (Figure 1). Myositis-specific antibody panel identified positive antinuclear matrix protein 2 (NXP2) autoantibody. Results of a whole-body computed tomography scan were normal except for subcutaneous and soft-tissue edema (Figure 2).Figure 2Computerized tomography of neck, sagittal (A); chest, axial (B); abdomen, axial (C): Generalized subcutaneous edema (asterisks) consistent with anasarca. Hypodense, nonenhancing prevertebral soft tissue thickening with pressure effect on the oropharynx (arrow heads).View Large Image Figure ViewerDownload Hi-res image Download (PPT) Despite the lack of classic skin rash, the severe diffuse subcutaneous and soft-tissue swelling should raise the suspicion for edematous myositis, which is mostly dermatomyositis.1Duchesne M. Leonard-Louis S. Landon-Cardinal O. et al.Edematous myositis: a clinical presentation first suggesting dermatomyositis diagnosis.Brain Pathol. 2020; 30: 867-876PubMed Google Scholar Subcutaneous edema, calcinosis, and dysphagia are common features of anti-NXP2 antibody-associated dermatomyositis.2Albayda J. Pinal-Fernandez I. Huang W. et al.Antinuclear matrix protein 2 autoantibodies and edema, muscle disease, and malignancy risk in dermatomyositis patients.Arthritis Care Res (Hoboken). 2017; 69: 1771-1776Crossref PubMed Scopus (75) Google Scholar Dysphagia could be from pharyngeal muscle weakness, esophageal calcinosis,3Jerome R. Sebastien H. Nadine M.B. An unusual cause of dysphagia.Gastroenterology. 2020; 158: e3-e5Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar or prevertebral soft-tissue swelling, as demonstrated in this patient. Prompt identification of anti-NXP2 antibody in patients with dermatomyositis and these distinct clinical features can serve as useful prognostic markers and guidance for further management. Dr Chompoopong conceptualized the study, gathered data, and drafted the manuscript for intellectual content. Dr Liewluck conceptualized the study and revised the manuscript for intellectual content. Dr McMenomy revised the manuscript for intellectual content. Dr Harper conceptualized the study and critically edited the manuscript. Download .docx (.01 MB) Help with docx files Appendix