An interactive journey through the human genome to understand why the neurons that produce dopamine die — and what role genes like LRRK2 and GBA play.
The entire journey of this page, summarized in steps.
Before diving into the genetics, it helps to understand the condition these genes help explain.
Parkinson's disease is a progressive neurodegenerative disorder caused by the loss of the dopaminergic neurons of the substantia nigra, in the midbrain. Its pathological hallmark is the Lewy bodies: aggregates of misfolded α-synuclein protein. The lack of dopamine explains the characteristic motor symptoms. It is the second most common neurodegenerative disorder after Alzheimer's.
In 1817, the British physician James Parkinson published "An Essay on the Shaking Palsy", the first detailed clinical description. Decades later, Lewy bodies (1912) and the dopamine deficit (1960) — the basis of modern treatment — were identified.
Symptoms fall into several categories; many non-motor ones can precede diagnosis by years:
Resting tremor, muscle rigidity, bradykinesia (slowness of movement) and postural instability. These are the basis of clinical diagnosis.
Anosmia (loss of smell), constipation, REM sleep behavior disorder (acting out dreams) and depression. They often appear years before the tremor.
In late stages, cognitive decline and dementia may appear. Not everyone develops them, and when they do, it is usually long after motor onset.
About 90% of cases. With no single inherited cause: it results from the combination of aging, many common small-effect variants and environmental factors.
Autosomal dominant forms. LRRK2 (G2019S) is the most common dominant cause; SNCA mutations and multiplications also cause the disease.
Recessive forms that appear before age 50. PRKN (parkin) and PINK1 impair the clearance of damaged mitochondria (mitophagy).
Parkinson's advances slowly over the years; each person progresses differently.
Years before the tremor: loss of smell, constipation, REM sleep behavior disorder and depression.
Motor symptoms appear, often on just one side of the body. Good response to treatment.
Symptoms become bilateral; medication fluctuations and balance problems emerge.
Greater dependence, possible falls and, in some cases, cognitive decline. Multidisciplinary care.
Treatments relieve symptoms greatly for years, but they still do not stop the neurodegeneration.
Levodopa (a dopamine precursor) and dopamine agonists: the mainstay of symptomatic treatment. Highly effective, especially early on.
DBS implants electrodes that modulate motor circuits; useful in selected cases with fluctuations that are hard to control with drugs.
Physical therapy, speech therapy, occupational therapy and exercise: they improve mobility, voice and quality of life throughout the disease.
Educational content with a scientific basis (James Parkinson 1817; Lewy bodies; dopamine deficit; current clinical practice). It does not replace assessment by a healthcare professional.
DNA (deoxyribonucleic acid) is the molecule that stores the genetic instructions of every living thing, spread across roughly 3 billion base pairs.
Four bases — A, T, C and G — form the double helix. In Parkinson's, certain variants in specific genes alter how neurons degrade proteins and maintain their mitochondria, making them more vulnerable to degeneration.
Parkinson's genes are spread across the entire genome. Click a chromosome to see its regions, the evidence and the genes involved.
Monogenic and risk genes of Parkinson's disease. Search and filter by cellular mechanism; click a card to see its function and the studies.
Parkinson's genes converge on a few processes within the neuron. Hover over a node to identify the gene; click to see the details.
From the first description of the "shaking palsy" to the 90 risk loci and therapies targeting GBA and LRRK2.
How Parkinson's genes damage the dopaminergic neurons of the substantia nigra.
The disease primarily affects a small region of the midbrain: the substantia nigra, where the neurons that produce dopamine reside. Click each region to see its role.
α-synuclein is a normal protein of nerve terminals. The problem arises when it misfolds and aggregates. Compare the two states.
In most cases, Parkinson's is sporadic: it is not directly inherited. Only about 15% of people have a family history.
GBA and LRRK2 variants are the most important genetic factors; even so, many carriers never develop the disease. The rest of the risk comes from hundreds of common small-effect variants and from environmental and aging factors.
The essentials about the genetics of Parkinson's disease:
The most important point: having a risk variant does not mean you will develop Parkinson's. Genetics informs risk and, above all, opens the door to targeted therapies already being investigated for GBA and LRRK2.
Parkinson's has no single cause. Some factors are associated with higher risk and others appear protective, but none causes or prevents it on its own:
The fact that something is associated with lower risk in population studies is not a recommendation: tobacco causes many other diseases. Stress or a one-off blow does not cause Parkinson's; the disease is multifactorial (genes + environment + aging).
Genetics is transforming how we understand, diagnose and treat Parkinson's.
Antibodies and vaccines are being developed that recognize misfolded α-synuclein to slow its aggregation and spread. The big goal: a therapy that modifies the course of the disease, not just the symptoms.
LRRK2 inhibitors and GBA modulators (such as ambroxol) aim to treat people according to their genetic profile, opening the door to a "personalized" Parkinson's.
Seed amplification assays detect pathological α-synuclein in cerebrospinal fluid, making it possible to identify the disease biologically, even in prodromal stages.
Combining biomarkers, smell, REM sleep and genetics to identify risk years before the tremor, when a therapy could be more effective.
Strategies to bolster mitophagy (PINK1/parkin) and lysosomal autophagy, the pathways where many Parkinson's genes converge.
Transplantation of iPSC-derived dopaminergic neurons and gene therapy (GDNF, AADC) to restore dopamine, in early trials.
Research is advancing fast and some of these results are preliminary: the dates and specific data may change as the trials mature.
The questions that come up most when learning about the genetics of Parkinson's.
Milestones and scientific sources on which this page is based.
This is an educational synthesis page; it is not a primary clinical source. For medical decisions, consult professionals and official resources on Parkinson's disease.
Six questions to check what you take away. It grades itself: tap an answer and you'll instantly see whether you got it right, with the explanation.