A study identified the typical pathologic features of dermatomyositis (DM) associated with anti-Mi-2 autoantibodies (anti-Mi-2 DM).

The observations from the study were described as follows-

• Higher severity scores in muscle fibre and inflammatory domains were found in patients with anti-Mi-2 DM than non-Mi-2 DM patients.
• The more frequent presence of perifascicular necrosis, increased perimysial alkaline phosphatase activity, and sarcolemmal membrane attack complex deposition was reported in patients with anti-Mi-2 DM.
• No significant differences in the percentages of the features mentioned above between the patients with anti-Mi-2 DM and those with ASS were found after Bonferroni correction.

Thus the researchers concluded that the previously reported features of ASS- Perifascicular necrosis and perimysial pathology are common in patients with anti-Mi-2 DM. This observation assists in differentiating anti-Mi-2 DM from other DM subtypes and also suggests the possibility of an overlapping mechanism between anti-Mi-2 DM and ASS.

Source:  Tanboon J, Inoue M, Hirakawa S, Tachimori H, Hayashi S, Noguchi S, Suzuki S, Okiyama N, Fujimoto M, Nishino I. Pathologic Features of Anti-Mi-2 Dermatomyositis. Neurology. 2021 Jan 19;96(3):e448-e459. doi: 10.1212/WNL.0000000000011269. Epub 2020 Dec 4. PMID: 33277422.