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Paraneoplastic syndromes (PNS) are a group of rare disorders caused by the presence of tumors in the body. They occur in about 10 to 15 percent of people with cancer and may develop before cancer is discovered.

Read on to learn what paraneoplastic syndromes are, what cancers they’re associated with, what common symptoms they have, and how they’re diagnosed and treated.

PNS is a set of symptoms distinct from those of cancer. They occur because you have cancer and can outlast cancer itself. While PNS are caused by tumors, they’re not related to the size or number of tumors in the body.

PNS are caused by an altered immune response to a tumor in your body. There are generally six main types of PNS, based on the body system they affect:

  • Endocrine. These affect the glands and hormones of your body.
  • Neurological. These affect the brain and nervous system.
  • Musculoskeletal. These affect muscle and bone.
  • Cutaneous. These affect the skin and connective tissues.
  • Hematological. These affect blood and blood cells.
  • Other. These syndromes include those that affect multiple body systems or that don’t fit into another category.

The symptoms of paraneoplastic syndrome depend on the specific body system or organ that the condition impacts.

Common symptoms include:

  • fever (most common)
  • night sweats
  • loss of appetite
  • weight loss (which can lead to muscle wasting)
  • altered sense of taste

Less common PNS may involve other body systems and organs such as the:

Brain and nervous system

PNS that affect the brain and nervous system may cause:

  • dizziness
  • double vision
  • seizure
  • changes to how you think and act
  • problems sleeping
  • trouble swallowing or speaking
  • muscle weakness
  • Impaired nerve function
  • less coordination, reflexes, or sensation

Endocrine glands

PNS that affect the endocrine glands may lead to high levels of the hormones cortisol and adrenocorticotrophic hormone (ACTH) and may cause the following symptoms:

  • headache
  • muscle cramps
  • irritability
  • drowsiness
  • nausea and vomiting
  • fatigue
  • weakness
  • confusion
  • slow heart rate
  • high blood pressure
  • coma
  • weight gain
  • fatty deposits around your midsection and face and in between your shoulders and upper back
  • swollen hands or legs
  • low blood sugar
  • low blood sodium or calcium levels
  • acute kidney failure

Skin

Flushed skin or redness and itching occur most often, but some syndromes can cause other skin issues, such as:

  • itching
  • flaky skin
  • hair loss
  • abnormal hair growth
  • tightening of the skin
  • black or brown pigmentation of the skin
  • skin rash
  • skin ulcers

Musculoskeletal system

Syndromes that affect the musculoskeletal system may cause:

  • pain
  • joint swelling and stiffness
  • muscle weakness and soreness
  • clubbed fingers

Blood

Too few red blood cells or too many platelets and white blood cells may cause:

  • unusually pale skin
  • fatigue
  • trouble breathing
  • blood clot in a deep vein, especially if found in more than one site
  • increased red blood cell count
  • abnormal circulating blood proteins

Digestive tract

PNS may cause diarrhea that persists. This can cause low protein levels in your blood from too much protein released through your stool.

Kidneys

PNS that affect the kidneys may alter the balance of acids and alkalines in your body, a system known as the acid-base balance. When this system becomes unbalanced, it can lead to kidney damage and other serious health problems and may even be fatal.

Symptoms may include:

  • swelling of both legs
  • fluid retention
  • excessive protein in urine

PNS occur when a tumor releases hormones or proteins that target certain body systems.

They may also occur when proteins known as antibodies or white blood cells called T cells attack your healthy cells instead of cancer cells. This is a type of autoimmune response.

Squamous cell cancer and small cell lung cancer (SCLC) are most often tied to these syndromes, but they can also show up in cancers of the:

Prior to any testing, your doctor will collect your complete medical history and perform a physical exam. Your doctor and healthcare team may also order several other types of tests, including:

Blood tests

Blood tests your doctor may order include:

Marker tests

Markers are substances made by cancer cells or normal cells set off by cancer in your body. Tumor or cancer markers may also be found in your blood, urine, or other body tissue.

Other tests

Your doctor may order other tests to help diagnose which PNS you have and how it’s affecting your body systems and organs. These tests may include:

  • imaging studies of your brain, chest, abdomen, pelvis, or breasts
  • skin or muscle biopsy

There’s no known way to prevent these syndromes, but actions that lower your overall risk for cancer may also help keep these syndromes at bay.

Your risk goes up if you’re middle-aged and if you have a close blood relative who has cancer or who’s had it in the past.

The first course of action is to treat cancer itself. Other treatment options may involve:

  • Corticosteroids. These medications may help ease swelling and reduce your body’s overactive immune system response.
  • Immunosuppressive drugs. These medications help to reduce your body’s autoimmune response as well.
  • Intravenous immunoglobulins (IVIG). These medications are giving by an IV (into your vein), and they help limit the number of antibodies in your blood.
  • Plasmapheresis. This is a process that filters out antibodies from the plasma, or liquid part, of your blood.
  • Physical and speech therapy. These therapies may help improve speech, swallowing, and movement helping you function better longer.

The outlook for an individual with a paraneoplastic syndrome depends on the type of cancer they have and cancer stage they are in when diagnosed and the specific PNS they have. There’s no cure for PNS, and damage to the body and to individual organs may be permanent. A person may die as a result of their cancer or from the effects of a PNS.

PNS associated with lung cancers tend to have more serious outcomes. A 2019 review on paraneoplastic pemphigus (one type of PNS) noted there was a high mortality rate due to:

  • severe infections such as sepsis and pneumonia
  • type of cancer often involved
  • autoimmune response that blocks air from passing through small airways in your lungs.

A 2019 study of the quality of life and survival in people with Lambert-Eaton myasthenic syndrome (LEMS) found that people lived longer if they had both LEMS and SCLC instead of SCLC alone.

However, some PNS may go away on their own.

PNS are a group of rare disorders caused by an altered immune response to tumors in the body.

These syndromes are a set of distinct symptoms with the most common being fever. Many body systems and organs may be involved.

Diagnosis may involve performing a wide array of tests, such as imaging studies of your brain, chest, abdomen, pelvis, and breasts and lab studies of your blood and urine.

Treatments aim to relieve symptoms, reduce any swelling, and suppress the body’s immune response to these syndromes.