BTG3 and infection: Laboratory evaluation demonstrated severe Coombs-positive hemolytic anemia (hemoglobin 5.8 g/dL, reticulocytosis, high LDH, undetectable haptoglobin) and marked thrombocytopenia, whereas immunologic testing revealed high-titer ANA, anti-dsDNA positivity, and low complement levels; infections, thrombotic microangiopathy, and malignancy were excluded.