Multiple Myeloma Symptoms: CRAB Explained

This page is for people with multiple myeloma, or worried about it, and their families. It lists the warning signs that need urgent care, then explains the common symptoms.

• You have new, severe back pain along with leg weakness, numbness, tingling, or a change in bladder or bowel control. Call 911 or go to the nearest emergency department. ACS calls this a medical emergency and says to contact your doctor right away or go to the emergency room. This combination can mean spinal cord compression, and delay can leave permanent nerve damage, so it needs treatment now rather than a call to the clinic. See Spinal Cord Compression During Cancer Care.
• You have a fever of 100.4°F (38°C) or higher during or after treatment, especially with a known low white blood cell count. Call your care team right away, day or night, and go to an emergency department if you cannot reach them quickly. Call 911 or go to the nearest emergency department if you also feel faint, shaky or short of breath. NCI describes infection during cancer treatment as life threatening and needing urgent medical attention. Chills, a sore throat, mouth sores, burning when you urinate, redness at a catheter site or any other sign of infection also mean call right away, even with a normal temperature. A normal temperature is not permission to wait. See Neutropenic Fever During Cancer Treatment.
• You have sudden confusion, dizziness, or vision changes, or you are hard to wake. Call 911 or go to the nearest emergency department. This can signal hyperviscosity, thickened blood. ACS calls it a medical emergency.
• You have extreme thirst with confusion, severe drowsiness, or significant weakness. This can be severe hypercalcemia (high blood calcium). Confusion or being hard to wake means: call 911 or go to the nearest emergency department. Thirst and weakness on their own still need a call to your care team right away.
• A bone breaks with little or no clear injury, or pain suddenly increases at a specific bone. Call your care team right away.
• You vomit blood or coffee-ground material, pass black or tarry stool, bleed heavily, or suddenly cannot urinate at all. Call 911 or go to the nearest emergency department.

None of these should wait for a scheduled appointment. Use your care team's emergency plan, and if you cannot reach them quickly, go to an emergency department.

Multiple myeloma is a cancer of plasma cells, a type of white blood cell that normally makes antibodies to fight infection. Abnormal plasma cells build up in the bone marrow. They crowd out healthy blood cells, produce an abnormal protein, and can damage bone and kidneys. Doctors often summarize the main effects using the acronym CRAB.

CRAB stands for Calcium (high), Renal (kidney problems), Anemia, and Bone disease: the four main types of organ damage myeloma can cause.

Calcium. Damaged bone releases calcium into the blood faster than the kidneys can clear it. This causes hypercalcemia, or high blood calcium. It can cause:

• Extreme thirst and frequent urination
• Dehydration
• Constipation and abdominal pain
• Loss of appetite
• Weakness
• Drowsiness or confusion

Renal, meaning kidney. The abnormal protein made by myeloma cells, along with high calcium, can damage the kidneys. Early kidney damage may cause no symptoms at all. As it progresses, it can cause weakness, shortness of breath, itching, and swelling in the legs.

Anemia. Myeloma crowds out normal blood cell production, lowering red blood cells. This causes fatigue, weakness, shortness of breath, and dizziness.

Bone disease. Bone pain, most often in the back, hips, or skull, is one of the most common myeloma symptoms. Bones can also weaken and break more easily, sometimes with only minor stress.

• Low platelets, raising the risk of bruising and bleeding.
• Low healthy white blood cells, raising infection risk.
• Hyperviscosity: thickened blood from a high level of the abnormal protein. This can cause confusion, dizziness, and stroke-like symptoms.
• Rarely, amyloidosis, where antibody proteins build up in organs and nerves such as the kidney and heart.

• Do I currently have any CRAB features, and how are they being monitored?
• What is my calcium level right now?
• How is my bone health being tracked?
• What back or nerve symptoms mean I should go to the emergency department?
• What should I do if I develop a fever?

• National Cancer Institute — Plasma Cell Neoplasms (Including Multiple Myeloma) Treatment (PDQ®)–Patient Version
• American Cancer Society — Signs and Symptoms of Multiple Myeloma