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Objective: To estimate the incidence and prevalence of Ro/SSA-positive subacute cutaneous lupus erythematosus (SCLE) in Stockholm County, Sweden (1.8 million inhabitants) and to investigate the frequency of photosensitivity and other clinical manifestations associated with Ro/SSA autoantibodies., Methods: Ro/SSA-positive patients in Stockholm were identified via registry-based searches. All patients who tested positive for the presence of Ro/SSA autoantibodies during 1996-2002 (n = 1,323; 85% women) were identified. A questionnaire was sent to all patients still living in Stockholm in 2003 (n = 1,048). Patients who reported having skin symptoms and photosensitivity (n = 125) underwent a clinical examination., Results: Of the 741 (71%) of 1,048 Ro/SSA-positive patients who responded to the questionnaire, 400 (54%) reported having photosensitivity, and of these patients, 125 agreed to be clinically examined. A diagnosis of LE was confirmed in 59 of the 125 patients (SCLE in 20, systemic LE [SLE] in 33, and chronic CLE in 6). Eighty-six patients reported experiencing symptoms consistent with polymorphous light eruption (PLE). Comorbidities such as cardiovascular disease, autoimmune disease, and other skin diseases were common. The incidence of Ro/SSA-positive SCLE during the study period was estimated to be 0.7 cases per 100,000 persons per year and the prevalence was approximately 6.2-14 in 100,000 persons., Conclusion: The incidence of Ro/SSA-positive SCLE in Stockholm County, Sweden is estimated to be 0.7 per 100,000 persons per year as compared with an incidence of SLE in Sweden of 4.8 per 100,000 persons per year. The prevalence is estimated to be 6.2-14 in 100,000 persons. Self-reported photosensitivity commonly corresponds to a history of PLE in Ro/SSA-positive patients, even when the clinical profile of SCLE is absent. Photoprotection should therefore be included in the treatment recommendations for these patients.

Anti-Ro/SSA assays assist the clinician in distinguishing autoimmune diseases such as Sjögrenś syndrome (SS), systemic lupus erythematosus (SLE) and subacute cutaneous lupus erythematosus (SCLE). The objective of the study was to investigate the fine specificity of the autoantibodies in relation to clinical presentation as well as environmental and endogenous factors such as photosensitivity, smoking and immunoglobulin (Ig) levels in patients with Ro/SSA autoantibodies. Serum samples from 96 anti-Ro/SSA positive photosensitive patients were tested for autoantibody levels by enzyme-linked immunosorbent assay (ELISA) using purified recombinant Ro52 kd, Ro60 kd and La proteins as antigens. The highest levels of anti-Ro52 and anti-La were observed in patients with primary SS, and the lowest levels of anti-Ro52 in chronic cutaneous lupus erythematosus (CCLE). SCLE patients with systemic disease (SLE and/or SS) showed higher levels of anti-Ro52 than SCLE limited to the skin. A correlation between high serum levels of IgG and anti-Ro52 (P < 0.01) and between IgA and anti-Ro52 (P < 0.05) and anti-Ro60 (P < 0.05) was found. Polymorphic light eruption (PLE) was common in all diagnostic groups but did not correlate with autoantibody levels. Smoking was more common in lupus patients than in SS patients. Our findings thus propose different mechanisms for different clinical presentations of Ro/SSA positive patients. The testing of anti-Ro52 antibodies might serve as a prognostic tool in photosensitive cutaneous diseases.