Myositis Specific Autoantibody | Anti-p155/140 [8] | Anti-MJ | Anti-synthetase (including anti-Jo-1) | Anti-Mi-2 | Anti-MDA-5 [9] |
---|---|---|---|---|---|
Autoantigen Target | TIF-1 | NXP-2 | Histidyl-tRNA synthetase | Mi-2 | CADM140 |
Frequency | 18–30% | 15–20% | 2–4% | 2–10% | 6% (UK) – 38% (Japan) |
JIIM subgroup (predominant) | JDM | JDM > JPM | JDM > Overlap CTD > JPM | JDM | JDM |
Median age at onset (years) | 7 (4–10) | 6 (4–8) | 14 (10–14) | 11 (6–12) | 6 (4–10) |
Race/ethnicity | White | White | White>Black | Hispanic | Variable, case reports in Japan |
Skin | Classic rash, photosensitive rash, cutaneous ulceration | Classic rash | Mechanics hands, Raynauds | Classic rash | Palmar papules, cutaneous ulceration |
Weakness | Moderate | Severe | Mild/moderate | Mild | May be amyopathic |
Muscle enzyme elevation | Low | Moderate | Moderate | High | Mild |
Additional musculoskeletal features | Muscle atrophy | Muscle cramps, joint contractures | Arthritis/ arthralgias | Less Common | Arthritis |
Major organ involvement | Less common | Dysphagia, GI ulceration | Interstitial lung disease | Less common | Interstitial lung disease |
Complications | Calcinosis (30%), lipodystrophy | Highest rate of calcinosis (47%) | Less calcinosis (10%), lipodystrophy (33%) | Calcinosis (18%) | Calcinosis (27%) |
Prognosis | Chronic course, low mortality | Chronic course, 1/3 monocyclic, low mortality | Highest risk of mortality | Best prognosis | Poor prognosis in Japan cohort |
References | 4,5,7,11 | 4,5,7 | 4,5,7 | 4,7 | 6,7, 9,10,12 |