Reference — Hematology
Multiple Myeloma Reference
A cancer of plasma cells that takes over the marrow and eats away the bone. One mnemonic carries the whole clinical picture: CRAB— Calcium up, Renal failure, Anemia, Bone lesions.
Educational use only. Chemotherapy, transplant, and supportive regimens are individualized and provider-directed. This reference is an educational aid. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
What It Is
Multiple myeloma is a malignant proliferation of plasma cells (mature antibody-producing B cells) in the bone marrow. The malignant clone pumps out a single useless antibody — the monoclonal (M) protein — detectable in serum, while its light chains (Bence Jones protein) spill into the urine and damage the kidneys. It mainly affects older adults and is currently treatable but not curable.
The CRAB Features
| Feature | Why it happens / what to watch |
|---|---|
| C — hyperCalcemia | Bone breakdown releases calcium → confusion, constipation, polyuria, cardiac effects; needs aggressive hydration |
| R — Renal failure | Light chains (Bence Jones protein) + hypercalcemia damage the kidneys |
| A — Anemia | Marrow crowding by plasma cells → fatigue, pallor, dyspnea |
| B — Bone lesions | Osteolytic 'punched-out' lesions → bone pain, pathologic fractures, vertebral collapse |
Also expect recurrent infections (functional antibodies are lacking despite high total protein) and hyperviscosity from excess M-protein (blurred vision, headache, bleeding).
Nursing Priorities
Hydration is central — generous fluids dilute calcium and protect the kidneys from light chains; monitor intake/output and renal function. Give bisphosphonates (zoledronic acid, pamidronate) to slow bone breakdown and treat hypercalcemia (watch renal function and for osteonecrosis of the jaw — dental clearance first). Protect fragile bones: careful handling, fall prevention, and pain control, because pathologic fractures and vertebral collapse are common. Implement infection precautions and watch for cord compression (new back pain with neuro changes = emergency).
NCLEX Pearls
- ✦Multiple myeloma = plasma-cell cancer; CRAB = hyperCalcemia, Renal failure, Anemia, Bone lesions.
- ✦M-protein in serum; Bence Jones (light chains) in urine; 'punched-out' lytic bone lesions.
- ✦Hydration is the priority — protects kidneys and lowers calcium.
- ✦Bisphosphonates slow bone destruction (watch for jaw osteonecrosis — dental clearance first).
- ✦Bones are fragile: handle carefully, prevent falls; new back pain + neuro signs = cord compression.
- ✦High total protein but poor immunity — infection is a major risk.
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with AABB (transfusion standards) · American Society of Hematology (ASH). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →