The C.R.A.B criteria defines certain symptoms of multiple myeloma, such as calcium elevation. They are an important tool that doctors use to help diagnose multiple myeloma and determine its progression.

Multiple myeloma is a type of cancer that affects the plasma cells, which are a type of white blood cell. It causes the cells to produce abnormal proteins.

As the disease progresses, it can cause fatigue, weight loss, weak bones, kidney problems, and anemia.

Several different markers can reveal to a doctor whether a person has multiple myeloma and, if they do, how much it has progressed. These markers include calcium elevation, renal insufficiency, anemia, and bone abnormalities. Doctors may refer to them as C.R.A.B. symptoms.

This article discusses C.R.A.B. symptoms and what they mean for people with multiple myeloma.

Vials of blood to be tested for markers of C.R.A.B. symptoms.Share on Pinterest
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C.R.A.B symptoms are signs of multiple myeloma. C.R.A.B is an acronym for:

  • Calcium elevation
  • Renal insufficiency
  • Anemia
  • Bone abnormalities

Doctors use these criteria to diagnose multiple myeloma. They consider people who have one or more C.R.A.B. symptoms or multiple infections to require treatment for the disease.

A doctor will use different techniques to check for each of the C.R.A.B symptoms.

Calcium elevation

Calcium elevation, or hypercalcemia, is when an individual has high levels of calcium in their blood. About 28% of people with multiple myeloma have hypercalcemia.

Common symptoms include:

  • nausea
  • vomiting
  • poor appetite
  • constipation
  • increased thirst
  • muscle weakness or twitching
  • fatigue
  • mental confusion
  • bone pain

Learn more about hypercalcemia.

Renal insufficiency

Renal insufficiency refers to poor kidney function, which may happen as a result of reduced blood flow to the kidneys.

Some symptoms of poor kidney function include:

  • fatigue
  • difficulty concentrating and sleeping
  • dry and itchy skin
  • frequent urination
  • blood in the urine
  • foamy urine
  • puffy eyes
  • swollen ankles and feet
  • poor appetite
  • muscle cramps
  • decreased urine output
  • dark urine

Learn more about kidney failure.


Anemia is the term for a low red blood cell (RBC) count. It affects about 73% of people with multiple myeloma.

These blood cells transport oxygen around the body. If a person’s RBC count is too low, their tissues and organs do not receive enough oxygen.

The symptoms of anemia include:

  • feeling cold
  • dizziness or lightheadedness
  • fatigue
  • irritability
  • shortness of breath
  • frequent headaches
  • chest pain
  • pallor, which will be more apparent in people with light skin

Learn more about anemia.

Bone abnormalities

Bone abnormalities may include lesions or areas of damage. They can lead to symptoms such as:

  • bone pain, particularly in the back and hips
  • bone weakness
  • osteoporosis
  • frequent bone fractures

According to research, most people with multiple myeloma have C.R.A.B. symptoms. Therefore, these symptoms are a useful diagnostic tool.

The four categories of C.R.A.B. symptoms have varying levels of incidence. A 2017 study found that among the participants, 68% had bone disease, 57% had anemia, 29% had renal failure, and 6% had calcium elevation.

However, this study was not extensive, including just 113 people with symptomatic multiple myeloma. Although the split of male and female participants was relatively even, the study did not disclose their race.

More research is necessary to determine the prevalence of C.R.A.B. symptoms in a more diverse population. It is particularly important to investigate the prevalence among Black people, who are twice as likely as white people to develop multiple myeloma.

Aside from C.R.A.B. symptoms, there are other signs to indicate that a person may have multiple myeloma. These include low blood counts, nerve damage, and thick blood.

Low blood counts

Anemia — the hallmark of which is a low RBC count — is one of the C.R.A.B symptoms. However, people with multiple myeloma can have low counts of other blood cells.

It is common for people with multiple myeloma to have shortages of white blood cells, which is called leukopenia.

With leukopenia, the body cannot fight off infections properly. As a result, some people with multiple myeloma have frequent infections, such as pneumonia.

People with multiple myeloma may also have a low platelet count, which is called thrombocytopenia. Platelets, which are responsible for blood clotting, play an essential role in wound healing. Having a low platelet count puts a person at risk of severe bleeding from minor cuts, scrapes, or bruises.

Nervous system symptoms

If multiple myeloma weakens the bones forming the spinal column, a person may experience spinal cord compression.

Weak spinal bones can collapse, pressing on spinal nerves. When this happens, the individual may experience sudden, severe back pain, muscle weakness, and numbness in the legs.

This condition is a medical emergency requiring immediate treatment.


Increased numbers of abnormal myeloma proteins can cause the blood to thicken, which is called hyperviscosity.

The thick blood does not flow properly, and it can cause reduced blood flow to the brain. This reduction in blood flow can result in dizziness, confusion, and the symptoms of a stroke, such as slurred speech and weakness on one side of the body.

People with any multiple myeloma symptoms, including C.R.A.B. symptoms, should contact their doctor.

Some symptoms of multiple myeloma, such as anemia, are relatively common, so they do not necessarily mean that someone has the condition. However, even if a person does not receive a multiple myeloma diagnosis, their symptoms may require treatment.

If someone has symptoms of spinal cord compression, it is crucial to seek medical attention right away to avoid permanent paralysis.

The outlook for people with multiple myeloma depends on how much the disease has progressed when they receive their diagnosis. According to the National Cancer Institute, the overall 5-year relative survival rate for myeloma is 55.6%.

This statistic means that someone with myeloma is 55.6% as likely as an individual without the condition to live for 5 years following their diagnosis.

When doctors detect the cancer at an early stage, the survival rate is higher. The 5-year relative survival rate for localized myeloma — which has not metastasized to other parts of the body — is 77.5%.

Various other factors affect someone’s outlook, including:

  • Age: Older individuals with multiple myeloma do not live as long with the condition.
  • Kidney function: If an individual’s kidneys become damaged, the outlook is less positive.
  • General health: Individuals with health problems, such as heart disease or diabetes, may have a less favorable outlook.

Learn more about the outlook for people with multiple myeloma.

Many people with multiple myeloma present with C.R.A.B symptoms. This acronym stands for calcium elevation, renal insufficiency, anemia, and bone abnormalities.

Although these are not the only symptoms of multiple myeloma, they are very common. Additional symptoms include low blood counts, nervous system symptoms, nerve damage, and thickened blood.

Anyone who notices any multiple myeloma symptoms should contact a doctor. The earlier someone begins treatment, the better their outlook.