Table 1 Summary of the main features of MSAs and MAAs
Antibody | Antigen | IP | IIF | Clinical association | |
|---|---|---|---|---|---|
Proteins (kDa) | RNA | HEp-2 | |||
Myositis-specific autoantibodies (MSAs) | |||||
 Anti-Jo-1 | Histidyl-tRNA synthetase | 50 | tRNAHis | Cytoplasmic fine speckled | Classic anti-synthetase syndrome with more frequent muscle involvement |
 Anti-PL-7 | Threonyl-tRNA synthetase | 80 | tRNAThr | Cytoplasmic dense fine speckled | Anti-synthetase syndrome with prevalent ILD |
 Anti-PL-12 | Alanyl-tRNA synthetase | 110 | tRNAAla | Cytoplasmic dense fine speckled | Anti-synthetase syndrome with prevalent ILD |
 Anti-EJ | Glycyl-tRNA synthetase | 75 | tRNAGly | Cytoplasmic speckled | Anti-synthetase syndrome |
 Anti-OJ | Isoleucyl-tRNA synthetase | 150 + 170/130/75 | tRNAIso | Cytoplasmic speckled | ILD alone or anti-synthetase syndrome |
 Anti-KS | Asparaginyl-tRNA synthetase | 65 | tRNAAsp | Cytoplasmic speckled | ILD alone or anti-synthetase syndrome |
 Anti-Zo | Phenylalanyl-tRNA synthetase | 60/70 | tRNAPhe | Cytoplasmic speckled | Myositis |
 Anti-YRS/HA | Tyrosyl-tRNA synthetase | 59 | tRNATyr | Cytoplasmic speckled | Myositis |
 Anti-Mi-2 | Nucleosome Remodelling Deacetylase (NuRD) (Mi-2α/β) | 240 + 200/150/75/65/63/50/34 |  | Fine speckled | Classical DM |
 Anti-SAE | Small ubiquitin-like modifier activating enzyme (SAE1/2) | 40/90 |  | Fine speckled | Severe cutaneous disease that classically precede DM with severe dysphagia and systemic symptoms |
 Anti-MDA5 (anti-CADM140) | Melanoma Differentiation-Associated gene 5 (MDA5) | 140 |  | Negative or Cytoplasmic speckled | Hypo-amyopathic, ILD with possible RP-ILD and severe and peculiar skin involvement |
 Anti-TIF1γ/α (anti-p155/p140) | Transcription intermediary factor 1 (TIF1γ/α) | 155/140 |  | Fine speckled | Juvenile DM. Cancer-associated hypo-myopathic DM |
Anti-TIF1β | Transcription intermediary factor 1β | 120 |  | Fine speckled | DM |
 Anti-NXP2 (anti-MJ) | Nuclear matrix protein (NXP-2) | 140 |  | Fine speckled and/or multiple nuclear dots | Juvenile DM, diffused calcinosis. Cancer-associated DM |
 Anti-SRP | Signal recognition particle | 72/68/54/19/14/9 | 7SL | Cytoplasmic dense fine speckled | IMNM with frequent esophageal involvement. Possible ILD |
 Anti-HMGCR | HMG-CoA reductase | 200/100 |  | Negative or Cytoplasmic speckled | IMNM with or without history of statin exposure |
Myositis-associated autoantibodies(MAAs) | |||||
 Anti-PM-Scl | Exosome protein complex (PM/Scl75/100) | 75/100 |  | Nucleolar homogeneous | Overlap PM/SSc |
 Anti-C1D | Exosome associated protein |  |  |  | Overlap PM/SSc |
 Anti-U1-RNP | U1 small nuclear RNP | 11–70 | U1 | Coarse speckled | MCTD |
 Anti-fibrillarin (anti-U3-snRNP) | Fibrillarin | 34 | U3 | Nucleolar clumpy | SSc |
 Anti-Ku | DNA-PK regulatory subunit | 70/80 |  | Fine speckled | PM/SSc. Potentially severe ILD |
 Anti-Ro52 | Ro-52/TRIM21 | 52 |  | Negative, fine speckled or cytoplasmic speckled | ILD. Frequently coupled with other MSA |
 Anti-Ro60/SSA | Ro-60/SS-A | 60 |  | Fine speckled | SjS, SLE |
 Anti-La/SSB | SS-B | 48 |  | Fine speckled | SjS, SLE |
 Anti-cN-1A (anti-Mup44) | Cytosolic 5′nucleotidase 1A |  |  |  | sIBM |
Miscellaneous | |||||
 Anti-RuvBL1/2 | RuvBL1/2 complex | 48/49 |  | Speckled | SSc, PM, Morphea |
 Anti-Su/Ago2 | Argonaute 2 | 100/102 and 200 |  | Cytoplasmic discrete dots | ILD in absence of cancer. Frequently coupled with MSA, Ro-52 and other antibodies |
 Anti-SMN | Survival of Motor Neuron | 38 + 130/120/33 |  | Few nuclear dots | PM/SSc |
 Anti-NUP | Nup358/RanBP2, gp210, Nup90, p200/p130, Nup62 |  |  | Punctate nuclear envelope | Subgroup of PM/SSc patients (so called NUP-syndrome). PBC |
 Anti-mitochondrial (AMA-M2) | Branched-chain α-ketoacid dehydrogenase complex |  |  | Cytoplasmic reticular/AMA | Long-lasting myositis with muscle atrophy and cardiac involvement. PBC |
 Anti-KJ | Translocation factor | 30/43 |  | Cytoplasmic speckled | Anti-synthetase-like syndrome |
 Anti-Fer (anti-eEF1) | Eukaryotic elongation factor 1 |  |  |  | Anti-synthetase-like syndrome |
 Anti-Wa |  | 48 |  | Cytoplasmic speckled | Anti-synthetase-like syndrome |
 Anti-Mas | selenocysteine seryl-tRNA-protein complex | 48 | tRNA[Ser]Sec | Cytoplasmic speckled | Non-immune mediated rhabdomyolysis. Autoimmune hepatitis |
 Anti-PMS | DNA repair mismatch enzyme (PMS1, PMS2, MLH1) |  |  |  | Mild myositis |
 Anti-cortactin | Cortactin | 68 |  |  | PM. Myasthenia gravis |
 Anti-FHL1 | Four-and-a-Half LIM domain 1 |  |  |  | Myositis and muscular atrophy with severe systemic involvement |