Sickle cell disease (SCD) is a prevalent genetic disorder that includes sickle cell anemia (hemoglobin SS), hemoglobin SC, and hemoglobin Sb-thalassemia. Patients with SCD present with a defective activation of the alternate pathway of the complement system that increases the risk of capsulate bacteria infection and failure to eliminate antigens, predisposing these patients to autoimmune diseases. The authors describe three patients with SCD that developed systemic lupus erythematosus (SLE). In all patients, SLE diagnosis was delayed because symptoms were initially attributable to SCD. Physicians should be alerted to the possible development of SLE in patients with SCD to not delay the diagnosis and start appropriate treatment.