Pla2G6 Associated Neurodegeneration (Plan) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
PLA2G6-associated neurodegeneration (PLAN) is a group of rare autosomal recessive neurodegenerative disorders caused by mutations in the PLA2G6 gene (Phospholipase A2, Group VI).[1] This condition encompasses a spectrum of phenotypes ranging from severe infantile-onset disease to adult-onset dystonia-parkinsonism.[2]
PLA2G6 encodes calcium-independent phospholipase A2 (iPLA2-VI), an enzyme crucial for phospholipid metabolism and mitochondrial function in neurons.[3] Loss of iPLA2-VI activity leads to impaired membrane remodeling, mitochondrial dysfunction, and progressive neuronal death.
The three main phenotypes within the PLAN spectrum include:
- Infantile Neuroaxonal Dystrophy (INAD) - Classic early-onset form
- Atypical Neuroaxonal Dystrophy (aNAD) - Intermediate form with later onset
- Adult-Onset Dystonia-Parkinsonism (ADP) - Adult-onset form
| Property |
Value |
| Gene Symbol |
PLA2G6 |
| Chromosomal Location |
22q12.1-q13.2 |
| Protein |
Calcium-independent phospholipase A2 (iPLA2-VI) |
| Inheritance |
Autosomal Recessive |
| OMIM |
603604 |
Over 100 pathogenic variants have been identified in PLA2G6, including missense, nonsense, splice-site, and frameshift mutations.[1] Common founder mutations have been described in various populations.[8]
The iPLA2-VI enzyme catalyzes the hydrolysis of the sn-2 position of phospholipids, releasing fatty acids including arachidonic acid, a precursor for pro-inflammatory eicosanoids.[3] Loss of enzymatic function leads to:
- Accumulation of phospholipid peroxidation products
- Mitochondrial dysfunction and energy failure[3]
- Impaired membrane trafficking
- Oxidative stress in neurons
- Progressive axonal degeneration
INAD presents in the first 2 years of life with:[4]
- Motor regression - Loss of previously acquired motor skills
- Hypotonia - Decreased muscle tone
- Ataxia - Coordination difficulties
- Spasticity - Muscle stiffness
- Nystagmus - Involuntary eye movements
- Visual impairment - Often due to optic atrophy
- Seizures - Present in ~50% of cases
- Cognitive decline - Progressive intellectual deterioration
Typical disease course shows rapid progression with loss of ambulation within 2-3 years of onset. Most individuals do not survive beyond adolescence.
aNAD presents between ages 2-10 years with:[2]
- Gait instability and clumsiness
- Speech delay or regression
- Behavioral changes including irritability
- symptoms** that progress **Mild motor more slowly than INAD
- Seizures in some cases
Disease progression is slower than INAD, with survival into adulthood possible.
ADP presents in adolescence or adulthood with:[5]
- Dystonia - Involuntary muscle contractions, often affecting neck and limbs
- Parkinsonism - Tremor, bradykinesia, rigidity
- Cognitive impairment - Variable, often mild
- Psychiatric symptoms - Depression, anxiety
This form has a more indolent course compared to the childhood-onset forms.
Diagnostic criteria include:
- Progressive neurodegenerative course
- Characteristic MRI findings (see below)
- Family history consistent with autosomal recessive inheritance
- Exclusion of other similar conditions
MRI findings in PLAN:[6]
- Cerebellar atrophy (especially vermis)
- Iron accumulation in the globus pallidus (T2 hypointensity)
- White matter abnormalities
- Thin or absent corpus callosum in severe cases
- Optic nerve atrophy on orbital MRI
- Sequencing of the entire PLA2G6 coding region
- Deletion/duplication analysis to detect copy number variants
- Prenatal testing available for families with known mutations
Elevated neurofilament light chain (NfL) in cerebrospinal fluid has been reported as a biomarker of disease progression.
There is currently no disease-modifying therapy for PLAN. Treatment is supportive and symptomatic:
- Antiepileptic drugs for seizure control
- Muscle relaxants for spasticity (baclofen, benzodiazepines)
- Dopaminergic agents for parkinsonism (may provide partial benefit in ADP)[5]
- Physical therapy to maintain mobility
- Occupational therapy for daily activities
- Speech therapy for communication difficulties
- Assistive devices as needed (wheelchairs, communication aids)
Research directions include:[7]
- Gene therapy - AAV-mediated PLA2G6 delivery
- Small molecule iPLA2 inhibitors - To reduce toxic lipid accumulation
- Antioxidant therapy - To combat oxidative stress
- Mitochondrial protectants
- Neurotrophic factors - To support neuron survival
| Phenotype |
Typical Course |
Life Expectancy |
| INAD |
Rapid progression |
Death in childhood/adolescence |
| aNAD |
Intermediate progression |
Survival to adulthood |
| ADP |
Slow progression |
Normal or near-normal lifespan |
- Estimated prevalence: 1 in 1,000,000 to 1 in 2,000,000
- Higher incidence in populations with founder mutations
- Equal male-to-female ratio
- No ethnic predilection for most mutations
Mouse models with PLA2G6 knockout show:
- Age-dependent neurodegeneration
- Motor deficits
- Iron accumulation
- Mitochondrial dysfunction
These models are being used to test experimental therapeutics.[7]
Current research focuses on:
- Understanding genotype-phenotype correlations
- Developing biomarkers for clinical trials
- Gene therapy approaches using AAV vectors[7]
- Small molecule modulators of iPLA2 activity
- Repurposing existing drugs for symptomatic benefit
The study of Pla2G6 Associated Neurodegeneration (Plan) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Gregory A, et al. PLA2G6 mutations and phenotype spectrum. Mov Disord. 2008;23(11):1596-1601.
- Kurian MA, et al. Clinical heterogeneity and genotype-phenotype correlations in PLAN. Brain. 2008;131(Pt 3):689-701.
- Wu Y, et al. iPLA2-VI and neurodegeneration. Biochim Biophys Acta. 2009;1791(8):776-782.
- Ii K, et al. Infantile neuroaxonal dystrophy: MR findings. AJNR Am J Neuroradiol. 2009;30(2):E18.
- Paisan-Ruiz C, et al. PLA2G6 mutations causing adult-onset dystonia-parkinsonism. Neurology. 2012;79(1):44-50.
- Chiu WZ, et al. Neuroimaging in PLAN. J Neurol Sci. 2011;300(1-2):87-90.
- Wenger DA, et al. Gene therapy approaches for PLAN. Mol Ther. 2017;25(5):1062-1074.
- Bohlega SA, et al. PLA2G6 founder mutation in Middle Eastern population. Neurology. 2014;82(1):89-92.