The prevalence of antinuclear antibodies in patients with apparent polymorphic light eruption.

Polymorphic light eruption (PLE) is a very common photosensitive disorder, the most important differential diagnosis of which is lupus erythematosus (LE). One-hundred and forty-two patients with PLE were screened for circulating antinuclear (ANA), Ro and La antibodies over a 2-year period. Results were negative in 66 patients. Sixty-two patients had low-titre ANA of various patterns, ranging from trace to 1/80 without evidence of LE although one later developed subacute cutaneous LE. Fourteen had more significant findings, six with ANA ranging from 1/160 to 1/1280 but no anti-Ro antibodies, four with ANA ranging from 1/160 to 1/1280 and also with anti-Ro antibodies and four patients with anti-Ro antibodies but low-titre ANA, one of whom later developed discoid LE. Three of these 14 patients fulfilled the American Rheumatism Association criteria for the diagnosis of systemic LE, but it was not certain in any of the patients whether the PLE-like rash represented cutaneous LE or coincidental PLE. However the overall 10% incidence of definite or possible LE in patients with suspected PLE suggests that all PLE patients should be screened for LE.