Systemic Sclerosis blot (Antibodies to: Scl-70, CENP-A, CENP-B, RPII, RP155, Fibrillarin (U3 RNP), NOR90, Th/To, PM-Scl75, Ku, PDGFR (platelet derived growth factor receptor), Ro52).

Immunology

---

Description

Systemic sclerosis (SSc) is an autoimmune connective tissue disease which causes cutaneous changes, microvascular abnormalities and visceral fibrosis (1). SSc is divided onto limited and diffuse forms: The limited form affects the skin of the distal extremities. In the diffuse form (also known as proximal systemic sclerosis) patients may present with widespread and rapidly progressing skin thickening over the trunk, proximal and distal extremities and the face. They may also have internal organ involvement affecting the connective tissue of the lungs, kidneys, oesophagus and heart (1,2,3,5). SSc specific autoantibodies can aid in early diagnosis and differentiation of the disease types and may be present in more than 95% of patients (1, 3).

The 1980 American College of Rheumatology criteria for diagnosis of SSc did not use the presence of SSc specific antibodies as major or minor criterion for diagnosis, therefore was not particularly sensitive for early diagnosis or in patients with the limited form. The joint ACR –EULAR group published new diagnostic criteria for SSc in 2013 (2) which does put weight on the presence of autoantibodies as well as the typical clinical manifestations for diagnosis.

Scl-70 (DNA topoisomerase I) is present in up to 42% of SSc patients (1). Strongly associated with diffuse SSc but may be seen in some patients with the limited form. Increased risk of pulmonary fibrosis and cardiac involvement. Patients with Raynauds disease and positive Scl-70 are at higher risk of developing SSc (1).

CENP-A and CENP-B (Centromere protein –A and –B) are the most comment autoantibodies detected in SSc. Centromere antibodies may also be observed in other autoimmune conditions such as SLE, PBC and Sjogrens syndrome. Patients with Raynauds disease and positive centromere antibodies are at higher risk of developing SSc (1). Centromere antibodies are usually indicative of limited SSc. They can be associated with both forms of the disease.

Fibrillarin (U3-RNP) antibodies are detected in 4-10% of SSc patients and are associated with diffuse SSc. They are more frequently observed in African-American populations than Caucasian or Asian cohorts. They are associated with severe pulmonary disease, pulmonary hypertension, small bowel involvement and a poor prognosis (1, 3).

NOR90 (Nucleolus organising region) is not considered to be sensitive for SSc (3).

Th/To (7-2-RNP/7-2 RNA protein complex) are not highly specific for SSc but are primarily associated with limited SSc and increased frequency of pulmonary fibrosis and scleroderma renal crisis.

PM-Scl includes the major autoantigens PM-Scl75 and PM-Scl-100. Antibodies to PM-Scl75 and PM-Scl100 antigen are found in 50-70% of patients with the polymyositis/scleroderma overlap syndrome. PM-Scl75 is seen in 8% of patients with myositis and 3% of patients with systemic sclerosis but 25% of patients with scleroderma/myositis overlap syndrome (4). PM-Scl100 is not as closely associated with systemic sclerosis as PM-Scl75. Strong nucleolar staining with weak, fine speckled, nucleoplasmic staining can be seen on Hep2 immunofluorescence.

Ku antibodies are seen in a variety of diseases including systemic lupus erythematosus, mixed connective tissue disease, scleroderma and the polymyositis/scleroderma overlap syndrome (4). They are also seen in patients with pulmonary hypertension. They show fine speckled nuclear and nucleolar staining on Hep2 immunofluorescence and are of little diagnostic value

PDGFR (Platelet derived growth factor receptor) antibodies have a potential pathogenic role in tissue fibrosis via activation of fibroblasts but are a rarely seen in SSc (<5% of cases) (1).

RPII and RP155 (RNA polymerase III subunits) are part of the RNA polymerase III complex. Antibodies to RNA polymerase III are highly specific for SSc, particularly the diffuse form with increased risk of renal crisis

---

Indications

Investigation of Systemic Sclerosis (diffuse and limited forms of the disease).

---

Sample Type

2mL Serum (Gel 5mL Yellow tube) or 2mL Plasma (EDTA, heparin or citrate). Requests from outside Sheffield: Transport at ambient temperature via Royal Mail or Courier.

---

Reference Range

Negative = Normal

---

Turnaround Time

Within 10 days

---

Testing Frequency

Weekly

---

References

Kayser C and Fritzler MJ. Autoantibodies in systemic sclerosis: Unanswered questions. Front Immunol. 2015. 6: Article 167. [Ref 1]. Van den Hoogen F, Khanna D, Fransen J, Johnson SR, Baron M, Tyndall A, et al. 2013 classification criteria for systemic sclerosis: an American College of Rheumatology/European league against rheumatism collaborative initiative. Arthritis Rheum (2013) 65:2737-4710. [Ref 2]. Villalta D, Imbastari T, Di Giovanni, et al. Diagnostic accuracy and predictive value of extenced autoantibody profile in systemic sclerosis. Autoimmun Rev. 2012. 12(2): 114-120. [Ref 3]. PRU Handbook of Autoimmunity. 2007. 4th Edition. [Ref 4].

---

See Also

Hep 2; ENA; ENA types; Myositis screen

Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.