In multiple myeloma, the CRAB criteria include which combination of features?

• A. Calcium elevation, Renal failure, Anemia, Bone lesions
• B. Calcium elevation, Respiratory failure, Anemia, Bone lesions
• C. Calcemia reduction, Renal failure, Anemia, Bone lesions
• D. Calcium elevation, Renal failure, Anemia, Hepatic lesions

Answer: (A)

CRAB criteria describe the end-organ damage that signals active, treatable multiple myeloma: high calcium levels, kidney dysfunction, anemia, and bone lesions. Hypercalcemia arises from bone breakdown driven by myeloma cells, releasing calcium into the blood. Kidney impairment typically results from light-chain (Bence Jones) cast nephropathy and the overall effects of circulating proteins, plus dehydration and hypercalcemia can worsen it. Anemia comes from marrow infiltration by malignant plasma cells, which crowds out normal red blood cell production. Bone lesions reflect osteolytic activity driven by the tumor, seen as destructive areas on imaging. This combination—calcium elevation, renal impairment, anemia, and bone lesions—captures the characteristic end-organ damage of active disease, which is why it is the correct choice. The other options include features not part of the CRAB criteria, such as respiratory failure, low calcium, or hepatic lesions, which do not represent the classic end-organ effects of myeloma.