Scl-70

Anti–Scl-70 antibodies are considered a specific marker for the diffuse type of systemic sclerosis. However, these autoantibodies can be seen in SLE, ranging from 0% to 25% of patients. The serum antibody titers in patients with SLE are significantly lower than those observed in patients with systemic sclerosis.

Scl-70 is also known as Topoisomerase I Antibody.

Topoisomerase I antibodies were initially named Scl-70 based on immunoblot detection of a 70-kDa protein.

The prevalence of Scl-70 antibodies in SSc varies widely across geographies and ethnicities, ranging from 9% to 71%.

These antibodies are strongly associated with dcSSc but also occur in lcSSc.

The 2 main types of SSc are defined according to the pattern of skin involvement: limited cutaneous SSc (lcSSc) and diffuse cutaneous SSc (dcSSc). In lcSSc, skin thickening is present distal to the elbows and knees, and facial skin thickening may or may not be present. In contrast, dcSSc is characterized by thickening of the skin of the whole extremity, as well as that of the anterior chest, abdomen, and back, with or without facial skin involvement. Multiple organs, including the heart, lungs, gastrointestinal tract, and kidneys, can be affected in both forms, though organ involvement is generally less severe in lcSSc. CREST syndrome (calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia) occurs frequently in lcSSc but can also occur in longstanding dcSSc.

Furthermore, they are highly specific to SSc and are included in the 2013 ACR-EULAR classification criteria.

The presence of Scl-70 antibodies is associated with pulmonary and cardiac involvement as well as renal crisis and vascular complications. Therefore, these antibodies indicate a poor prognosis.

The increased mortality associated with Scl-70 antibodies results primarily from the higher risk for severe ILD (Interstitial lung disease is an umbrella term used for a large group of diseases that cause scarring --fibrosis-- of the lungs.)

References:

Kayser C, Fritzler MJ. Autoantibodies in systemic sclerosis: unanswered questions. Front Immunol. 2015;6:167. doi:10.3389/fimmu.2015.00167

Pokeerbux MR, Giovannelli J, Dauchet L, et al. Survival and prognosis factors in systemic sclerosis: data of a French multicenter cohort, systematic review, and meta-analysis of the literature. Arthritis Res Ther. 2019;21(1):86. doi:10.1186/s13075-019-1867-1

van den Hoogen F, Khanna D, Fransen J, et al. 2013 classification criteria for systemic sclerosis: an American College of Rheumatology/European League against Rheumatism collaborative initiative. Arthritis Rheum. 2013;65(11):2737-2747. doi:10.1002/art.38098

Stochmal A, Czuwara J, Trojanowska M, et al. Antinuclear antibodies in systemic sclerosis: an update. Clin Rev Allergy Immunol. 2020;58(1):40-51. doi:10.1007/s12016-018-8718-8

Hamaguchi Y, Takehara K. Anti-nuclear autoantibodies in systemic sclerosis: news and perspectives. J Scleroderma Relat Disord. 2018;3(3):201-213. doi:10.1177/2397198318783930