Serologic studies in patients with lupus erythematosus and psoriasis.

We present four patients with coexistent lupus erythematosus (LE) and psoriasis. This is an unusual combination. All four patients had antibodies to Ro, which were absent in twenty-four control psoriatics. Antibodies to Ro occur in only 25% to 30% of unselected SLE patients, but occur in approximately 60% of "antinuclear antibody (ANA)-negative" LE patients, many of whom are highly photosensitive. The increased frequency of anti-Ro in our patients suggests that this may be a specific serologic marker for the LE/psoriasis overlap. Also, since anti-Ro correlates with photosensitivity, LE/psoriasis overlap patients may be at increased risk for photosensitivity, which occurred in two of our patients, one of whom developed severe systemic disease following ultraviolet (UVB) phototherapy. Screening for anti-Ro antibodies may be appropriate in psoriatics prior to UVB phototherapy.