Application of the diagnostic criteria for systemic lupus erythematosus to patients with multibacillary leprosy

Introduction: Systemic lupus erythematosus (SLE) is a chronic inflammatory disease that affects multiple organs or systems. There is no pathognomonic clinical or laboratory test sensitive and specific enough for a specific diagnosis. The criteria proposed by the American College of Rheumatology (ACR), as modified in 1997, are used for the diagnosis. The presence of four or more criteria presents sensitivity and specificity of 96%. However, these diagnostic criteria for SLE may have lower specificity in areas that are endemic for chronic infectious diseases, such as Brazil (endemic for leprosy), which may have similar clinical and laboratory manifestations. Methods: A prevalence study was conducted, applying the SLE criteria to patients with recently diagnosed multibacillary leprosy who were registered at the leprosy outpatient clinic, Department of Dermatology, Federal University of Pernambuco (UFPE), during the data gathering period. The specificity and the number of false positives in this group were calculated. Results: One hundred patients were included. The prevalences of some of the SLE criteria were high. The criteria with the highest prevalence were malar erythema (44%), arthritis (23%), photosensitivity (29%), lymphopenia (19%) and presence of antiphospholipid antibodies, including immunological criteria (20%). The specificity found (84%) was lower than the specificity allocated to the criteria in 1997 by the ACR. Conclusions: Diseases in our setting, such as leprosy in multibacillary forms, mimic the clinical and laboratory characteristics of SLE, and thus physicians need to be aware of the realities of local infectious diseases before affirming a definitive diagnosis of SLE.