C4A and systemic lupus erythematosus: Laboratory findings indicated elevated total IgG levels (3,216 mg/dL), low C4 levels, and an elevated antinuclear antibody (ANA) titer (1:640) with a nuclear homogeneous pattern, with positivity for anti-dsDNA on enzyme-linked immunosorbent assay (ELISA) but negative on immunofluorescence. A comprehensive autoimmune panel, including antibodies associated with systemic lupus erythematosus, Sjögren’s syndrome, systemic sclerosis, and systemic vasculitis, was negative.