Analysis index

1 ml serum

negative

Suspicion of myositis, anti-synthetase syndrome

Ro-52:

Anti-Ro-52 is often positive in case of various collagenosis. No disease specificity. Ro-52 today is no longer assigned to the SS-A complex.

PM:

Autoantibodies against the target antigens PM-Scl75 and PM-Scl100 are seen in progressive systemic sclerosis (prevalence 7 % – 10 %), polymyositis and dermatomyositis (8 % – 12 %) as well as in patients with overlap syndrome of polymyositis/dermatomyositis and progressive systemic sclerosis (18 %).

Mi-2:

Antibodies against Mi-2 are a strong indicator for dermatomyositis. Figures are given for the prevalence between 16 % and 67 %. The prevalence in juvenile dermatomyositis is 4 % – 10 % (high titers are characteristic) and in polymyositis it is 1 %.

TIF1g:

Autoantibodies against TIF1gamma are associated with dermatomyositis. Its prevalence in adult patients with dermatomyositis is 21 %. In 50 % – 75 % of cases, there is a malignant neoplasm. Tumor screening is indicated! In juvenile dermatomyositis, prevalence is 23 % – 29 %. High titers are characteristic and tumor association rare.

SRP:

Antibodies against SRP (signal recognition particle) are found in

• Polymyositis, often with an acute onset and with severe course, prevalence 3 % – 5 % and in
• Necrotizing myopathy, prevalence 4 %. A participation of lungs, skin or joint is not described, in contrast to patients with antibodies against aminoacyl-tRNA synthetases.

Ku:

Autoantibodies against Ku occur in poly/dermatomyositis and progressive systemic sclerosis overlap syndrome, often accompanied by primary pulmonary hypertension. In addition to this, they are also detected in various myositis forms, in systemic lupus erythematosus and in progressive systemic sclerosis.

MDA5:

Melanoma differentiation associated gene 5, synonym IFIH1, interferon induced with helicase c domain 1. Autoantibodies against MDA5 are seen in approximately 20 % of patients with dermatomyositis. They are associated with clinically amyopathic dermatomyositis (CADM), which is often accompanied with an interstitial lung disease (ILD). Asians in particular appear to be affected by a rapid progressive form of ILD and a less favorable prognosis.

NXP2:

Nuclear matrix protein 2, 18 % – 23 % in juvenile dermatomyositis, 5 % in adult dermatomyositis.

SAE1:

SUMO activating enzyme subunit 1. 8 % in dermatomyositis, 5 % in dermatomyositis associated with interstitial lung disease (ILD).

Jo-1:

Autoantibodies against Jo-1 (Histidyl-tRNA synthetase) occur in polymyositis with a prevalence of 25 – 35 % and in dermatomyositis with a prevalence of 5 %. They are associated with the anti-synthetase syndrome, which is characterized by myositis, interstitial pulmonary fibrosis, Raynaud syndrome, arthritis, fever and so-called mechanic’s hands.

PL-7/-12:

Autoantibodies against the target antigens PL-7 (Thyreonyl-tRNA synthetase) and/or PL-12 (Alanyl-tRNA synthetase) indicate polymyositis/dermatomyositis. They have a prevalence of 3 % – 4 %. They belong to the anti-synthetase antibodies and are associated with interstitial pulmonary fibrosis.

OJ:

Anti-OJ antibodies (Isoleucyl-tRNA synthetase) are associated with polymyositis (prevalence < 5 %). They belong to the anti-synthetase antibodies and are associated with interstitial pulmonary fibrosis.

EJ:

Anti-EJ antibodies (Glycyl-tRNA synthetase) are very rare antibodies, which may occur in patients with anti-synthetase syndrome and may be associated with interstitial pneumonia.

HMGCR:

Antibodies against HMGCR (3-hydroxy-3-methylglutaryl-coenzyme A reductase) can be associated with an immune-mediated necrotizing myopathy (INM), in 2/3 of all patients, previous statin-exposure.

cN-1A:

Antibodies against cN-1A (cytosolic 5’-nucleotidase 1A) can be associated with an inclusion body myositis (IBM, in approx. 30 %), but were also found in patients with Sjögren-syndrome or SLE.