Pathophysiology refers to changes in bodily processes that result from disease. In the case of multiple myeloma (MM), which is a type of bone marrow cancer, the pathophysiology is complex. It can lead to bone, blood, kidney, and sometimes neurological problems.

MM pathophysiology has a widespread impact on the body. That is why an individual may require multiple blood tests, imaging tests, and biopsies for doctors to diagnose MM and determine a suitable treatment plan.

In this article, we discuss the pathophysiology of MM. We also look at the causes of the condition, as well as diagnosis and treatment options.

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MM is a type of bone marrow cancer that accounts for 1.8% of new cancers in the United States. Scientists believe, however, that cases of MM could almost double within the next 20 years.

MM is more common among people who are:

  • male
  • aged over 65 years
  • Black

MM causes bone symptoms, such as pain, fractures, and collapsed vertebrae, which may lead to a curved spine and spinal cord compression. Other serious health problems it can cause throughout the body include:

The pathophysiology of MM affects skeletal, blood, kidney, and neurological processes.

Skeletal processes

Skeletal complications are common in MM. Around 60% of people who have MM develop a bone fracture at some point.

MM can interfere with an important, lifelong process called bone remodeling. In this process, cells called osteoclasts dissolve older bone tissue, and cells called osteoblasts replace them with newer, stronger cells.

For bone remodeling to work, there must be a healthy balance between the osteoclast and osteoblast activity. Special bone cells called osteocytes are crucial here, as they regulate the activity of osteoclasts and osteoblasts.

People with MM have fewer useful osteocytes than average, which compromises bone remodeling, leading to bone problems, such as fractures and pain.

Hematologic processes

Hematology refers to the blood. When a person has cancer, their cells develop uncontrollably, resulting in many dysfunctional cells.

As MM cancer cells grow and proliferate within the bone marrow, it struggles to produce enough healthy blood cells. This can lead to conditions such as:

  • anemia, which occurs when a person has low levels of red blood cells
  • neutropenia, which is when the levels of white blood cells called neutrophils are low
  • thrombocytopenia, which is when there are low levels of platelets in the bloodstream

Kidney processes

Around 50% of people with MM have kidney problems when their MM produces symptoms. The mechanisms behind these kidney problems are complex and involve a harmful buildup of plasma cells in the urine.

Plasma cells are white blood cells, and MM can affect their production and growth. These cells can overwhelm the kidneys in people with MM, causing blockages, inflammation, and cell damage.

Neurologic processes

MM affects the nervous system in around 1% of people with the condition. This rare but serious complication occurs when white blood cells enter the central nervous system, cerebrospinal fluid, or meninges, which are the membranes covering the brain and spinal cord.

Scientists remain unsure about how exactly this process occurs. However, there is evidence that genetic mutations in tumor suppressor cells could play a role.

General processes

Experts understand the general processes driving MM. The condition belongs to a spectrum of disorders affecting the growth of long-lived plasma cells.

Before developing active MM, individuals pass through two earlier asymptomatic disease stages called monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM).

MGUS is the earliest stage with no active symptoms, and it is not cancer. People with MGUS have low levels of a blood protein called monoclonal protein, or M protein. Only 20% of individuals with MGUS progress to MM.

SMM is the stage between MGUS and MM. People with SMM have a higher level of M protein and more abnormal plasma cells in the bone marrow than with MGUS.

Scientists do not know the exact cause of MM. However, like all cancers, MM develops when genetic mutations cause particular cells to grow uncontrollably. In the case of MM, these cells are long-lived plasma cells, which can stay in the bone marrow for long periods.

Health experts know that genetic mutations in specific proteins, such as KRAS, BRAF, NRAS, and TP53, occur in many cases of MM, but what leads to these genetic mutations is unknown.

However, there is some evidence that various factors can make MM more likely, including:

Doctors need to perform various tests to diagnose MM, including:

According to research, there are several staging systems for MM, with modern staging systems measuring blood chemicals, such as:

  • albumin
  • serum-beta-2 microglobulin
  • lactate dehydrogenase

Thanks to new treatments and improved supportive care, survival rates for people with MM have significantly increased over the last few decades.

Some standard MM treatment options include:

Many cancer treatments carry a risk of significant side effects. For example, there is evidence that corticosteroids can cause such adverse effects as:

Similarly, chemotherapy often kills healthy cells in addition to cancer cells, leading to side effects, such as:

MM is a potentially serious type of bone marrow cancer. It can affect the bones, blood, kidneys, and brain.

Doctors may use numerous blood tests, imaging tests, and biopsies to diagnose the condition. Moreover, because MM is complex, an individual may require various treatments to improve their outlook.