Pantothenate Kinase-associated Neurodegeneration (PKAN) · What It Is, Causes, Signs and Symptoms, Treatment, and More

Pantothenate kinase-associated neurodegeneration (PKAN), formerly known as Hallervorden-Spatz disease, is a rare autosomal recessive subtype of neurodegeneration with brain iron accumulation (NBIA), characterized by movement dysfunction, dystonia, and progressive neurocognitive impairment. PKAN affects approximately 1 in 1 million individuals.  

Typical PKAN, also referred to as classic PKAN, is characterized by early onset of symptoms, usually before age 10, with rapid progression, resulting in the inability to ambulate within 10 to 15 years. In contrast, atypical PKAN typically presents in the second or third decades of life, with slower progression, resulting in the inability to ambulate within approximately 15 to 40 years. 

PKAN is a genetic disorder typically inherited in an autosomal recessive manner, meaning that two pathogenic variants—one inherited from each parent—are required for disease manifestation. 

The disorder is caused by mutations in the PANK2 gene, which is located on chromosome 20 and encodes the enzyme called pantothenate kinase. A kinase is an enzyme that catalyzes the addition of phosphate (-PO4) groups to a substrate. Pantothenate kinase plays a crucial role in the biosynthesis of coenzyme A (CoA), an essential metabolic cofactor involved in numerous cellular pathways, including lipid metabolism and mitochondrial function.   

In the first step of CoA synthesis, pantothenate kinase catalyzes the conversion of pantothenate to 4’-phosphopantothenate. In individuals with PKAN, impairment of this step leads to reduced CoA synthesis and widespread metabolic dysfunction. One consequence of impaired CoA availability is the accumulation of the amino acid cysteine and cysteine-containing compounds, which contributes to cellular toxicity. In addition, CoA deficiency disrupts cellular redox homeostasis, increasing susceptibility to oxidative stress, partly through impairment of antioxidant defenses, including glutathione-dependent pathways 
 
As a result, cysteine-containing compounds preferentially accumulate in iron-rich regions of the brain, particularly the basal ganglia. These deposits are most prominent in the globus pallidus and the pars reticularis of the substantia nigra, structures that play key roles in motor control and the regulation of voluntary movement.  

When cysteine-containing compounds interact with iron in these regions, auto-oxidation occurs, generating reactive oxygen species. Under normal conditions, antioxidants such as glutathione neutralize these free radicals and limit oxidative damage. In PKAN, impaired antioxidant capacity leads to excessive oxidative stress, progressive neuronal injury within the basal ganglia, and the development of movement disorders, dystonia, and neurocognitive decline. 

Most patients with PKAN present with progressive movement disorders. Common motor features include dystonia (i.e., involuntary, sustained muscle contractions), rigidity, bradykinesia (i.e., slowness of voluntary movement), hyperreflexia, dysarthria (i.e., difficulty speaking), and abnormal involuntary movements such as choreoathetosis (i.e., involuntary twitching or writhing). These symptoms collectively reflect a parkinsonian phenotype and are similar to those observed in Parkinson disease, although PKAN typically presents at a younger age and progresses more rapidly.  

Additional manifestations may include pigmentary retinopathy, which can lead to visual impairment or  blindness, as well as neurocognitive decline and intellectual disability. Neuropsychiatric symptoms, including behavioral changes, may also occur, particularly in individuals with atypical PKAN.  

The diagnosis of PKAN is based on a combination of clinical features, neuroimaging findings, and genetic testing. A detailed medical history and neurologic examination are essential to establish the age of symptom onset, pattern of progression, and the presence of characteristic movement abnormalities suggestive of basal ganglia involvement.  

Genetic testing is a critical component of diagnosis and can be performed either through single-gene testing when PKAN is strongly suspected or through multigene panels that include genes associated with neurodegeneration with brain iron accumulation (NBIA). In PKAN, pathogenic variants in the PANK2 gene confirm the diagnosis.     

Neuroimaging, particularly magnetic resonance imaging (MRI), often reveals a characteristic finding known as the eye-of-the-tiger sign. This sign, seen on T2-weighted images, consists of bilateral hypointensity of the globus pallidus due to iron deposition, surrounding a central region of hyperintensity reflecting neuronal loss and gliosis. Although highly suggestive of PKAN, this finding is not universally present, especially in atypical cases.  

Postmortem studies in individuals with PKAN, demonstrate marked atrophy and red-brown discoloration of the globus pallidus and pars reticularis of the substantia nigra, corresponding to iron accumulation and neurodegeneration. 

It is also important to consider and exclude alternative diagnoses. Other NBIA subtypes may present with overlapping clinical features but often show distinct neuroimaging patterns. For example, mitochondrial membrane protein-associated neurodegeneration (MPAN) may demonstrate cerebellar and cortical atrophy, while beta-propeller protein-associated neurodegeneration (BPAN) is associated with mixed hyperintense and hypointense signals in the substantia nigra. Non-NBIA disorders with similar movement phenotypes include Wilson disease and Huntington disease, both of which can be confirmed through targeted genetic testing. 

There is currently no disease-modifying therapy for PKAN; therefore, treatment is primarily supportive and focused on symptom management. Management is individualized and aims to alleviate motor symptoms, preserve function, and improve quality of life. 

Movement disorders associated with PKAN, including dystonia, rigidity, and parkinsonism, may be treated with dopaminergic agents such as levodopa or dopamine agonists (e.g., pramipexole), although clinical response is variable. Muscle relaxants, including baclofen, may help reduce stiffness, muscle spasms, and spasticity. Intramuscular botulinum toxin injections can be effective in relieving focal or segmental dystonia and are often used as symptom progress. Benzodiazepines such as clonazepam, which enhance gamma-aminobutyric acid (GABA)-mediated inhibitory neurotransmission, may be beneficial for choreoathetosis and other hyperkinetic movements.  

In individuals with severe, medically refractory movement disorders, deep brain stimulation (DBS), has shown promising results in selected cases. DBS involves surgical implantation of electrodes, typically targeting the basal ganglia structures involved in motor control, and is an established therapy for Parkinson disease. Although experience with DBS in PKAN is limited, emerging evidence from case reports and small series suggests potential benefits in reducing dystonia and improving motor function.  

Despite symptomatic treatments, the overall prognosis of PKAN remains poor, as neurocognitive decline is typically progressive and irreversible, and no therapies currently halt disease progression 
 
Although PKAN is characterized by iron accumulation and oxidative stress within the basal ganglia, iron chelation therapies (i.e., deferiprone) have shown reduction in brain iron accumulation but limited clinical benefit in controlled trials. Antioxidant supplementation has not demonstrated consistent clinical benefits.  

Given the complexity and high disease burden associated with PKAN, individuals often benefit from a multidisciplinary approach involving neurologists, physical and occupational therapists, speech and language pathologists, dietitians, nurses, and social support services. 
 

Pantothenate kinase-associated neurodegeneration (PKAN) is the most common subtype of neurodegeneration with brain iron accumulation (NBIA) and is a progressive neurodegenerative disorder characterized by movement abnormalities, dystonia, and neurocognitive decline.  

PKAN is caused by autosomal recessive inheritance of pathogenic variants in the PANK2 gene, which impairs the biosynthesis of coenzyme A and leads to metabolic dysfunction, oxidative stress, and iron accumulation in vulnerable brain regions.  

Clinically, PKAN often presents with progressive movement disorders, including dystonia, rigidity, bradykinesia, dysarthria, and choreoathetosis, frequently accompanied by cognitive impairment and, in some cases, visual dysfunction due to pigmentary retinopathy. The disease may present in childhood (classic PKAN) or later in adolescence or adulthood (atypical PKAN), with variable rates of progression. 

Diagnosis of PKAN is based on the combination of characteristic clinical features, neuroimaging findings, and genetic confirmation. MRIs often demonstrate the characteristic eye-of-the-tiger sign on T2-weighted images, reflecting iron deposition and neurodegeneration in the globus pallidus. Definitive diagnosis is established by genetic testing identifying pathogenic PANK2 variants. 

There is currently no disease-modifying treatment for PKAN, so management is supportive and focuses on symptomatic treatment of movement disorders using dopaminergic agents, benzodiazepines, muscle relaxants, intramuscular botulinum toxin, and, in selected cases, deep brain stimulation. Despite symptomatic therapies, PKAN remains a debilitating condition with progressive neurologic impairment, underscoring the importance of multidisciplinary care aimed at optimizing function and quality of life.