Extranodal lymphoid microstructures in inflamed muscle and disease severity of new‐onset juvenile dermatomyositis

• Published in: Arthritis and rheumatism 2009-04, Vol.60 (4), p.1160-1172
• Main Authors: López De Padilla, Consuelo M., Vallejo, Abbe N., Lacomis, David, McNallan, Kelly, Reed, Ann M.
• Format: Article
• Language: English
• Subjects: Adolescent; Antigens, CD20 - metabolism; B-Lymphocytes - metabolism; Biological and medical sciences; Biopsy; CD4-Positive T-Lymphocytes - metabolism; Chemokine CXCL13 - metabolism; Child; Child, Preschool; Chimerism; Dendritic Cells, Follicular - pathology; Dermatomyositis - genetics; Dermatomyositis - immunology; Dermatomyositis - pathology; Diseases of the osteoarticular system; Female; Humans; In Situ Hybridization, Fluorescence; Leukocyte Common Antigens - metabolism; Lymph Nodes - immunology; Lymph Nodes - pathology; Lymphotoxin-alpha - metabolism; Lymphotoxin-beta - metabolism; Male; Medical sciences; Muscle, Skeletal - immunology; Muscle, Skeletal - pathology; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; Severity of Illness Index; Skin - immunology; Skin - pathology; Venules - pathology; Young Adult
• ISSN: 0004-3591; 1529-0131
• DOI: 10.1002/art.24411

Objective Juvenile dermatomyositis (DM) is an autoimmune disease of childhood characterized by lesions in skin and muscle that are populated by plasmacytoid dendritic cells (PDCs) and lymphocyte infiltrates. We undertook this study to examine the cellular composition, organization, and molecular milieu of the cellular infiltrates in muscle in juvenile DM and to correlate the infiltrates with clinical disease manifestations. Methods Since PDCs and lymphocyte foci express CCL19 and CCL21, we investigated for in situ formation of lymphoid microstructures that could be sites of extranodal immune activation. Results Analyses of muscle biopsy samples from children with new‐onset juvenile DM showed 3 categories of lesions: diffuse infiltrates, lymphocytic aggregates lacking follicle‐like organization, and follicle‐like structures. The last of these exhibited elements of classic lymphoid follicles, including networks of follicular dendritic cells and high endothelial venules. They also expressed high levels of CXCL13 and lymphotoxins known to support lymphoid organogenesis. There were also resident naive CD45RA+ T cells and maternally derived B cells and PDCs. Patients with diffuse infiltrates or lymphocytic aggregates were responsive to standard therapy with steroids and methotrexate, but those with follicle‐like structures tended to have severe disease that required additional agents such as intravenous Ig or rituximab. Conclusion These data suggest that lymphoneogenesis is a component of the early disease process in juvenile DM. Ectopic lymphoid structures could indicate a severe course of disease; their early detection could be a tool for disease management.