The Myositis Profile IgG test is used to detect autoantibodies associated with inflammatory muscle diseases, such as polymyositis (PM), dermatomyositis (DM), and other autoimmune conditions. Here’s a breakdown of the components in your panel:

Understanding the Myositis Profile (IgG: 22)

The IgG: 22 likely refers to a measured immunoglobulin G level, but interpretation depends on the lab’s reference range.

Key Antigens and Their Significance

General Autoimmune Markers

1. ANA (Antinuclear Antibody) – Found in many autoimmune diseases, including systemic lupus erythematosus (SLE) and myositis.
2. dsDNA (Double-Stranded DNA) – Highly specific for lupus (SLE).
3. Histone – Associated with drug-induced lupus.
4. Nucleosome – Related to SLE and lupus nephritis.
5. P0 (Ribosomal P0 protein) – Linked to lupus with neuropsychiatric symptoms.

Centromere and Systemic Sclerosis Markers

6. CENP-A & CENP-B (Centromere Antigens A & B) – Found in limited systemic sclerosis (CREST syndrome).
7. Scl-70 (Topoisomerase I) – Associated with diffuse systemic sclerosis (scleroderma).

Myositis-Specific Autoantibodies (MSAs)

8. Jo-1 (Histidyl-tRNA Synthetase) – A marker of anti-synthetase syndrome, which includes myositis, interstitial lung disease (ILD), and arthritis.
9. PL-7 (Threonyl-tRNA Synthetase) – Associated with polymyositis/dermatomyositis (PM/DM) and ILD.
10. PL-12 (Alanyl-tRNA Synthetase) – Linked to myositis with ILD.
11. M2 (Mitochondrial M2 Antigen) – Found in primary biliary cholangitis (PBC).
12. PM-Scl (Polymyositis-Scleroderma Overlap) – Indicates overlap syndrome between myositis and scleroderma.

RNP and Sm Antibodies (Markers of Mixed Connective Tissue Disease and SLE)

13. RNP-68, RNP-A, RNP-C (Ribonucleoproteins) – High levels suggest Mixed Connective Tissue Disease (MCTD).
14. SmB & SmD (Smith Antibodies) – Highly specific for lupus (SLE).

Sjogren’s Syndrome & Lupus Markers

15. Ro52 & Ro60 (SSA Antibodies) – Associated with Sjogren’s syndrome, lupus, and congenital heart block in newborns.
16. La (SSB Antibody) – Seen in Sjogren’s syndrome and lupus.

Other Autoimmune Markers

17. PCNA (Proliferating Cell Nuclear Antigen) – Found in SLE with active disease.
18. DFS70 (Dense Fine Speckled 70 Antigen) – Often found in healthy individuals; if isolated, it may not indicate autoimmune disease.

How to Interpret Results?

• A positive result for Jo-1, PL-7, PL-12, PM-Scl, or Scl-70 may indicate an inflammatory muscle disease (myositis or scleroderma).
• If multiple antibodies are positive, it may suggest an overlap syndrome (e.g., myositis with scleroderma or lupus).
• Elevated ANA with RNP antibodies suggests mixed connective tissue disease (MCTD).