Purkinje Cell Cytoplasmic Antibody Type 2 (PCA-2)
What is PCA-2?
Purkinje Cell Cytoplasmic Antibody Type 2 (PCA-2) is a type of paraneoplastic antibody, which means it is made by the immune system in response to a tumor. However, instead of attacking the cancer directly, the immune system mistakenly targets healthy nerve cells in the brain—specifically, the Purkinje cells found in the cerebellum, the part of the brain responsible for coordination and balance.
Why is PCA-2 tested?
PCA-2 is typically tested when a person is experiencing unexplained neurological symptoms, especially if doctors suspect a paraneoplastic neurologic syndrome (PNS). These symptoms may include:
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Balance or coordination problems (ataxia)
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Muscle stiffness or spasms
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Memory or cognitive changes
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Sensory issues or numbness
A positive PCA-2 test can provide a clue that these symptoms may be caused by an autoimmune response related to an underlying cancer.
What does a positive PCA-2 result mean?
A positive PCA-2 result suggests the presence of a paraneoplastic syndrome and may be associated with an undiagnosed tumor, most often:
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Small cell lung cancer (SCLC)
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Other neuroendocrine or lung-related tumors
It does not confirm a cancer diagnosis, but it serves as a red flag for doctors to investigate further, often with imaging studies like a CT scan or PET scan.
What does a negative result mean?
A negative PCA-2 test means this specific antibody was not detected in your blood. However, this does not rule out all autoimmune or paraneoplastic causes. If symptoms continue, your doctor may recommend additional testing for other antibodies or perform a phenotype-specific paraneoplastic panel.
Why it matters
Identifying PCA-2 early can help doctors:
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Diagnose rare autoimmune brain conditions sooner
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Detect hidden cancers at an earlier stage
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Prevent further neurological damage through appropriate treatment
Purkinje Cell Cyto Ab Type 2
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