A patient with multiple myeloma on daratumumab requires urgent blood transfusion. The blood bank reports pan-reactivity against all panel cells and difficulty identifying compatible units. The most likely explanation is:

• A Development of warm autoimmune haemolytic anaemia from myeloma itself
• B Daratumumab binding CD38 on red cell surfaces, interfering with antibody identification panels ✓
• C Transfusion-associated graft-versus-host disease
• D Cold agglutinin disease caused by the underlying plasma cell dyscrasia

Explanation

CD38 is expressed weakly on erythrocytes, so therapeutic daratumumab coats patient red cells and mimics alloantibodies on the indirect antiglobulin test, producing apparent pan-agglutination and positive direct antiglobulin tests without true haemolysis. Blood banks resolve this by treating the patient's serum with dithiothreitol, which denatures CD38 and unmasks genuine alloantibodies. Warm AIHA and cold agglutinins cause actual haemolysis with spherocytes or complement coating, features absent here.

Reference: Williams Hematology, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.