CRMP-5 IgG Antibody
What is CRMP-5 IgG?
CRMP-5 IgG (also known as anti-CV2) is an autoantibody—an antibody that the immune system makes against the body’s own tissues. It targets a protein called CRMP-5 (Collapsin Response Mediator Protein 5), which is found in the nervous system. The presence of this antibody in the blood or cerebrospinal fluid can be a sign of an immune system reaction often linked to certain types of cancer.
Why is CRMP-5 IgG Important?
A positive CRMP-5 IgG result may point to a paraneoplastic neurologic syndrome (PNS)—a condition where the immune system reacts to a tumor by mistakenly attacking the nervous system. This antibody can be a clue to an undiagnosed cancer, especially when someone is experiencing unexplained neurological symptoms.
CRMP-5 IgG is most commonly associated with:
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Small cell lung cancer
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Thymoma (a tumor of the thymus gland)
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Less commonly, other cancers such as colon, breast, or prostate cancer
When is this Test Ordered?
Doctors may order the CRMP-5 IgG test if you have:
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Unexplained neurological symptoms (e.g., memory loss, balance issues, vision problems)
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Suspected autoimmune disease involving the brain, spinal cord, or nerves
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A known or suspected cancer, especially if neurological symptoms are present
What Does a Positive Result Mean?
A positive CRMP-5 IgG result suggests that your immune system may be reacting to a cancer somewhere in the body—even if it hasn’t yet been found. It does not confirm a cancer diagnosis on its own, but it is a strong indicator that further investigation is needed.
It may also help explain certain neurologic conditions caused by immune system activity rather than direct tumor growth.
What Does a Negative Result Mean?
A negative result means this specific antibody was not found. However, it does not rule out all forms of paraneoplastic or autoimmune neurologic disease. If symptoms continue, your doctor may recommend additional testing.
Next Steps
If CRMP-5 IgG is positive, your healthcare provider may:
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Order imaging tests to look for a tumor
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Refer you to a neurologist or oncologist
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Start treatment to manage immune-related nerve or brain symptoms
Summary
CRMP-5 IgG is an important biomarker that can help detect an autoimmune reaction linked to certain cancers. While it doesn’t confirm a diagnosis by itself, it provides valuable information that can guide further testing and treatment.
Always talk with your healthcare provider to understand what your test results mean for your specific health situation.
CRMP-5 IgG
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