@gw1997 My husband had 3 skin biopsies.

What is the skin biopsy looking for?

The biopsy looks for an abnormal protein called alpha-synuclein.

Everyone has alpha-synuclein in their nerves. The problem is that in diseases like:

* Lewy body dementia (LBD)
* Parkinson’s disease
* Multiple system atrophy (MSA)

the protein becomes misfolded and clumps together. These clumps damage nerve cells.

The biopsy specifically looks for phosphorylated alpha-synuclein (P-SYN), which is the abnormal form associated with these diseases.

How is the biopsy done?

It’s very simple.

Usually three tiny (3 mm) punch biopsies are taken from different places, such as:

* the back of the neck
* above the knee
* near the ankle

The procedure:

* takes about 15–20 minutes
* uses local anesthetic
* generally doesn’t require stitches (or just one tiny stitch)

The samples are sent to a specialized lab where they are stained and examined under a microscope.

Why the skin?

Our skin contains small nerve fibers.

Those nerves are actually extensions of the nervous system, and in Lewy body diseases, the abnormal alpha-synuclein travels into these peripheral nerves—not just the brain.

So instead of trying to biopsy the brain (which isn’t done in living people), doctors can examine these skin nerves.

How accurate is it?

The test is very good, but not perfect.

Studies have found approximately:

* 90–95% sensitivity (it detects most people who truly have a synuclein disorder)
* 95–100% specificity (a positive result is very unlikely in people without one)

It’s one of the strongest biological tests currently available for confirming that a person has a synucleinopathy.

What does a positive result mean?

A positive biopsy means the person has a disorder involving abnormal alpha-synuclein.

By itself, the biopsy cannot distinguish between:

* Lewy body dementia
* Parkinson’s disease
* Parkinson’s disease dementia
* Multiple system atrophy

The doctor combines the biopsy with the person’s symptoms.

For Steve, because he has:

* progressive dementia,
* visual-spatial problems,
* fluctuations,
* parkinsonian features,
* and the positive skin biopsy,

those findings together strongly support Lewy body dementia rather than Alzheimer’s disease alone.

Why is this such a big deal?

Until recently, doctors diagnosed Lewy body dementia mostly from symptoms, and many people were misdiagnosed as having only Alzheimer’s disease.

The skin biopsy provides objective biological evidence that abnormal alpha-synuclein is present, giving families and clinicians much greater confidence in the diagnosis.

One important point

The biopsy doesn’t tell how severe the disease is or predict exactly how quickly it will progress. It answers a different question:

“Is there abnormal alpha-synuclein in the nervous system?”

For many families, having that answer can explain why symptoms such as hallucinations, cognitive fluctuations, parkinsonism, sensitivity to certain medications, and changes in attention occur together.

Knowing the biopsy was positive helps make sense of why his condition has features that don’t fit typical Alzheimer’s disease alone, and why his care team has been adjusting medications with Lewy body disease in mind.