Based on these observations, he was finally diagnosed with SLE with rapidly progressive glomerulonephritis and acute interstitial pneumonitis based on the criteria defined by the American College of Rheumatology (ACR)[3,4] and Systemic Lupus International Collaborating Clinics (SLICC)[5]: leukopenia, lymphopenia, renal disorder, serositis, anti-dsDNA antibody, anti-nuclear antibody, low C3, and direct Coombs test. The gene discussed is C3; the disease is lymphopenia.