Adenosine deaminase in progressive systemic sclerosis.

The aim of the present study was to confirm the increase of adenosine deaminase (ADA) activity in progressive systemic sclerosis (PSS), described by Sasaki & Nakajima, and to compare plasma ADA activity of patients in different stages of the disease. Enzyme activity was measured with a colorimetric assay. The 48 patients were subdivided into 3 groups: subgroup 1 (n = 10), disease still limited to the skin; subgroup 2 (n = 21), involvement of the skin and oesophagus; and subgroup 3 (n= 17), involvement of the skin and multiple internal organs. ADA levels were highest in subgroup 3. However, the difference with respect to subgroup 2 did not reach statistical significance. Subgroup 1 was different from controls and subgroups 2 and 3 (p<0.001). Our results confirm that ADA activity is increased in PSS, and that this finding is observed even in the early stages of the disease process. We speculate that the increase in ADA, a well-known marker of T-cell activation, might be an indicator of disease activity in PSS, in the beginning as well as during phases of exacerbation in later stages of the disease.