Former Secretary of State Colin Powell, who died Monday at age 84 due to complications of COVID-19, had multiple myeloma, a blood cancer that impairs the body’s ability to fight infections and to respond well to vaccines.

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The cancer attacks plasma cells: white blood cells that make antibodies to protect from infections, according to the U.S. Centers for Disease Control and Prevention (CDC)

The cells grow too much in myeloma, crowding out normal cells in the bone marrow that produce platelets and red and white blood cells.

Multiple myeloma is the most common type of plasma cell tumor and develops in the bone marrow before potentially spreading throughout the body.

In this Feb. 15, 2001 file photo, Secretary of State Colin Powell looks on as President Bush addresses State Department employees at the State Department in Washington.

In this Feb. 15, 2001 file photo, Secretary of State Colin Powell looks on as President Bush addresses State Department employees at the State Department in Washington. (AP Photo/Kenneth Lambert)

Scientists don't know why some people get myeloma and others don't and age is the most significant risk for people developing the disease. 

People who are younger than 45 rarely develop it and men are more likely than women to do so. 

Additionally, myeloma is more than twice as common among Black people as among White people. 

In some cases, the CDC notes, exposure to X-rays or ionizing radiation may be a risk factor and being overweight or obese are also linked to higher risk. 

Symptoms of myeloma are varied and sometimes do not immediately appear. 

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Myeloma may be discovered when a blood or urine test is done for another condition and a higher than normal level of protein is found. 

More advanced symptoms include bone pain in the back or ribs, bones that break easily, fever for no known reason, frequent infections, bruising or bleeding easily, weakness of the arms or legs, tiredness and trouble breathing.

The Mayo Clinic says nausea, constipation, loss of appetite, mental fogginess, weight loss, excessive thirst and weakness or numbness in the legs are also signs of multiple myeloma.

The clinic said complications of multiple myeloma include reduced kidney function, bone problems and anemia.

The American Cancer Society (ACS) says it is difficult to diagnose multiple myeloma early as the disease often causes no symptoms until it reaches an advanced stage or vague symptoms that seem to be caused by other diseases.

If tests indicate the presence of multiple myeloma, a doctor will use the information from diagnostic testing to stage it using the Revised International Staging System (RISS).

There is no known way to prevent it, the ACS notes, though treatments include chemotherapy, radiation and stem cell transplants.

The National Cancer Institute showed multiple myeloma accounted for 1.8% of new cancers in the U.S. this year and reported that there have been 34,920 new cases. 

The cancer’s five-year survival rate, or the percentage of people who live five years or more after their initial cancer diagnosis, is 55.6% and around 2% of national cancer deaths are a result of multiple myeloma.

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Kathy Giusti, founder of the Multiple Myeloma Research Foundation, told The Associated Press that Powell had "connected with every patient, caregiver and doctor in the room" when he spoke to the advocacy group about his diagnosis in 2019.

In a statement, she said that in addition to receiving vaccinations, cancer patients should consider other precautions like mask-wearing and avoiding crowds. Powell's family said he had been fully vaccinated.

The Associated Press contributed to this report