The modified Rodnan skin score is an accurate reflection of skin biopsy thickness in systemic sclerosis

To test the ability of the modified Rodnan skin score to reflect skin thickness in skin biopsies from 141 patients with systemic sclerosis (SSc) obtained at entry during a prospective, double blind study of ketanserin versus placebo in SSc.

Punch skin biopsies (4 mm) were obtained from the dorsal surface of the distal forearm of 141 patients. Biopsy specimens were trimmed and weighed (wet weight) and then desiccated and reweighed (dry weight). Skin score was recorded for 17 areas, graded 0-4+, while edema was graded 0-4+ in 10 of the same sites using finger pressure.

Total skin score correlated with wet weight (r = 0.553) and dry weight (r = 0.517) of the skin biopsies. Local skin score from the biopsied forearm also correlated with wet and dry weight (r = 0.536 and 0.530, respectively). Dry weight as a percentage of wet weight was the same for diffuse cutaneous SSc (dSSc) and limited cutaneous SSc (lSSc) (30.7% for both, NS), despite increased wet weight in patients with dSSc versus lSSc (17.75 vs 13.03 g; p < 0.001). Edema scores correlated poorly both with wet weight (r = 0.069) and dry weight (r = 0.169).

Total and forearm skin score correlates well with both wet and dry forearm skin biopsy weight from forearm biopsies, indicating that skin score reflects the underlying pathology of SSc. Further, the percentage of dry to wet weight is similar for lSSc and dSSc, supporting the usefulness of skin score in differentiating SSc disease subtypes.