Complement levels C3 and C4 were collected and were both decreased at 46 mg/dL (75–175 mg/dL) and 8 mg/dL (22–45 mg/dL), respectively, initially suggestive of SLE as a diagnosis; however, C3 normalized to 76 mg/dL prior to discharge without intervention, arguing against SLE. The gene discussed is C3; the disease is systemic lupus erythematosus.