Alpha-synuclein disease includes a group of neurological conditions caused by the abnormal accumulation of a brain protein called alpha-synuclein. This buildup disrupts communication between brain cells and affects networks involved in movement, thinking, perception, sleep, and automatic body functions such as blood pressure and digestion.

It is a biological brain disease, not a psychiatric condition, and is one cause of dementia. However, not everyone with alpha-synuclein disease develops dementia.

What Is Alpha-Synuclein?

Alpha-synuclein is a normal protein that plays a role in nerve cell signaling and communication. In disease states, the protein misfolds and accumulates inside and around nerve cells. These abnormal protein deposits:

• Disrupt communication between brain cells
• Reduce efficiency of brain networks
• Interfere with the brain's ability to clear waste proteins

Over time, this leads to dysfunction in specific brain systems.

Why Do Symptoms Look So Different?

Symptoms vary based on which brain networks are affected first and most severely. Different networks control:

• Movement
• Attention and thinking
• Visual processing
• Sleep and dreaming
• Automatic body functions (blood pressure, bladder, digestion)

Because alpha-synuclein can affect these networks in different patterns, people may experience diverse symptoms, even though the underlying biology is the same.

Common Clinical Presentations of Alpha-Synuclein Disease

Alpha-synuclein disease can present in several recognizable patterns:

• Parkinson's disease - movement symptoms predominate early
• Cognitive-predominant presentations - early changes in attention, alertness, or perception
• Combined movement and cognitive presentations - both systems affected
• Autonomic-predominant presentations - blood pressure, bladder, and balance problems
• REM sleep behavior disorder - acting out dreams, often years before other symptoms

These are different expressions of the same protein disease, distinguished mainly by timing and pattern.

Why Do Symptoms Fluctuate?

Many people experience good days and bad days. This occurs because:

• Affected brain networks struggle to maintain consistent signaling
• Sleep, illness, stress, or medications can worsen symptoms
• Fluctuation does not necessarily mean rapid decline

What About Hallucinations?

Hallucinations can occur due to changes in visual processing networks. They are not caused by imagination or mental illness and may:

• Be mild or non-disturbing
• Come and go
• Worsen with certain medications

With careful management, hallucinations can often be reduced.

How Is Alpha-Synuclein Disease Different from Alzheimer's Disease?

• Alzheimer's disease typically affects memory first
• Alpha-synuclein disease more often affects attention, perception, movement, and sleep
• Memory may be relatively preserved early

Some individuals may have overlap of both protein diseases.

How Is Alpha-Synuclein Disease Evaluated?

Diagnosis is based on symptoms, neurologic examination, and cognitive testing. In some cases, alpha-synuclein pathology can be confirmed using skin biopsy or spinal fluid (CSF) testing, which directly assess the abnormal protein.

DaT scans measure dopamine function but do not directly detect alpha-synuclein and are not specific for alpha-synuclein disease. All results are interpreted in a clinical context.

What Can Be Treated?

There is no cure yet, but many symptoms can be managed, including:

• Movement difficulties
• Sleep problems
• Hallucinations
• Mood and anxiety
• Blood pressure instability

Care focuses on safety, independence, and quality of life.

What This Means

Alpha-synuclein disease is:

• Real and biologically based
• Variable in how it appears and progresses
• Best managed through ongoing partnership, monitoring, and adjustment

Understanding the protein biology helps reduce uncertainty and supports better care over time.