26th January 2024

Diagnosis

Limited or diffuse systemic sclerosis can be diagnosed in patients with skin thickening of the fingers and hands, which extend from the proximal interphalangeal joints to the metacarpophalangeal joints. In many cases, there would be positive anti-topoisomerase (anti-Scl-70) antibodies, anti-centromere or anti-RNA polymerase III antibody or a positive ANA (anti-nuclear antibody). 

In differentiating between both limited and cutaneous systemic sclerosis, it is important to note that patients with diffuse cutaneous systemic sclerosis will have widespread skin involvement, which includes proximal limbs and significant internal organ involvement. In addition, diffuse cutaneous systemic sclerosis would be more associated with Anti-Scl-70 (Anti-topoisomerase) or Anti-RNA polymerase III positivity. 

Investigations such as pulmonary function tests may show restrictive changes, while CT may show evidence of interstitial pulmonary disease. Echocardiography may reveal pulmonary arterial hypertension. Dermoscopy may show abnormal capillaries. 

Sine sclerosis is a rare autoimmune disease diagnosed in patients with no evidence of skin manifestations of systemic sclerosis but have positive clinical features such as Raynaud’s phenomenon, digital ischemia, abnormal capillaries, and pulmonary and renal involvement. It can be very difficult to diagnose due to the lack of external cutaneous manifestations; however, in these cases, antibodies such as ANA would be positive, but antibodies such as Anti-Scl-70 and Anti-centromere antibodies would be expected to be negative.  

Scleroderma overlap syndrome occurs in approximately 20% of patients where there is cutaneous sclerosis and features of another connective tissue disease (most often an inflammatory myopathy such as polymyositis and dermatomyositis). However, these patients can also have symptoms of other autoimmune illnesses such as rheumatoid arthritis, Sjogren’s syndrome and SLE. In these cases, it is more common to find other antibodies such as Anti-U1RNP, Anti-Ro, Anti-La and Anti-Jo rather than Anti-Scl-70 and Anti-centromere. 

Table 3: The American College of Rheumatology/European League Against Rheumatism criteria for the classification of systemic sclerosis (2013). It incorporates the clinical features of systemic sclerosis and corresponding scores for each aspect. A score of 9 or more is required to confirm the diagnosis.

Table 3: Hoogen et al. 2013 Classification Criteria for Systemic Sclerosis: An American College of Rheumatology/European League Against Rheumatism Collaborative Initiative. Arthritis & Rheumatism. 2013 Nov; 65 (11):2737-2747. Available from: https://www.rheumatology.org/Portals/0/Files/2013%20ACR%20EULAR%20SSc%20Classification%20Criteria_Complete%20article.pdf