A 35-year-old woman recovering from Mycoplasma pneumoniae pneumonia develops fatigue and dark urine. Smear shows clumped red cell aggregates, the direct antiglobulin test is positive for C3d only, and the thermal amplitude of the antibody is low. First-line management is:
- A High-dose corticosteroids
- B Splenectomy
- C Avoidance of cold exposure plus supportive care, with rituximab if severe ✓
- D Warm-reactive antibody adsorption and plasma exchange
Correct answer: C. Avoidance of cold exposure plus supportive care, with rituximab if severe
Explanation
Post-infectious cold agglutinin disease features IgM antibodies optimally active below 30 degrees B fixing complement, giving a B3d-only positive DAT. Management centres on keeping the patient warm; haemolysis is usually self-limiting as the IgM titre falls over weeks, with rituximab reserved for severe cases. Steroids are largely ineffective because hepatic clearance of B3-coated cells dominates, and splenectomy fails since IgM-coated cells are cleared mainly by liver Kupffer cells.
Reference: Williams Hematology, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.