Membrane attack complex deposits in cutaneous lesions of dermatomyositis

Clinico-Pathologic Conference: Case 6

“…Kissel et al [5] have suggested a complement-mediated pathway in DM-related vasculopathy. These findings were corroborated by other studies [6] that have demonstrated an increased perivascular and junctional deposition of membrane attack complex (C5b-9) in lesional skin biopsies of DM patients. Magro and Crowson [7] have shown that the vascular deposition of C5b-9, as shown by immunofluorescence, may be an important tool in differentiating DM from lupus.…”

Plasmacytoid dendritic cells are present in cutaneous dermatomyositis lesions in a pattern distinct from lupus erythematosus

“…Once recruited to sites of inflammation PDCs can serve as effector cells to elaborate cytokines related not only to vacuolar interface changes seen histologically in each disease, but also to a complement cascade resulting in C5b-9 seen along the dermal-epidermal junction in DM. 13 Most of our cases, of DM and LE showed evidence of chronic solar damage in the biopsy ( Table 1). The degree of solar elastosis did not correlate closely with the number or location of PDCs in tissue, suggesting that other mechanisms, either related to acute UV exposure or other factors, may be important in pathogenesis as well.…”

Photoimmunology of Lupus Erythematosus and Dermatomyositis: A Speculative Review

“…Components of the membrane attack complex of complement have recently been described to occur at the dermal-epidermal junction and microvasculature of DM skin lesions (101). Lesional dermalepidermal junction immunoglobulin or complement deposits have been reported to occur in 5-67% of patients depending upon the site of biopsy.…”