Genetic, clinical, and radiographic delineation of Hallervorden-Spatz syndrome

Deep brain stimulation for pediatric pantothenate kinase-associated neurodegeneration with status dystonicus: A case report and literature review

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) is a type of inherited metabolic disorder caused by mutation in the PANK2 gene. The metabolic disorder mainly affects the basal ganglia region and eventually manifests as dystonia. For patients of dystonia, their dystonic symptom may progress to life-threatening emergency--status dystonicus.

OBJECTIVE

We described a case of a child with PKAN who had developed status dystonicus and was successfully treated with deep brain stimulation (DBS). Based on this rare condition, we analysed the clinical features of PKAN with status dystonicus and reviewed the reasonable management process of this condition.

CONCLUSION

This case confirmed the rationality of choosing DBS for the treatment of status dystonicus. Meanwhile, we found that children with classic PKAN have a cluster of risk factors for developing status dystonicus. Once children diagnosed with similar neurodegenerative diseases are under status dystonicus, DBS can be active considered because it has showed high control rate of this emergent condition.

Mitochondrial iron deficiency triggers cytosolic iron overload in PKAN hiPS-derived astrocytes

Disease models of neurodegeneration with brain iron accumulation (NBIA) offer the possibility to explore the relationship between iron dyshomeostasis and neurodegeneration. We analyzed hiPS-derived astrocytes from PANK2-associated neurodegeneration (PKAN), an NBIA disease characterized by progressive neurodegeneration and high iron accumulation in the globus pallidus. Previous data indicated that PKAN astrocytes exhibit alterations in iron metabolism, general impairment of constitutive endosomal trafficking, mitochondrial dysfunction and acquired neurotoxic features. Here, we performed a more in-depth analysis of the interactions between endocytic vesicles and mitochondria via superresolution microscopy experiments. A significantly lower number of transferrin-enriched vesicles were in contact with mitochondria in PKAN cells than in control cells, confirming the impaired intracellular fate of cargo endosomes. The investigation of cytosolic and mitochondrial iron parameters indicated that mitochondrial iron availability was substantially lower in PKAN cells compared to that in the controls. In addition, PKAN astrocytes exhibited defects in tubulin acetylation/phosphorylation, which might be responsible for unregulated vesicular dynamics and inappropriate iron delivery to mitochondria. Thus, the impairment of iron incorporation into these organelles seems to be the cause of cell iron delocalization, resulting in cytosolic iron overload and mitochondrial iron deficiency, triggering mitochondrial dysfunction. Overall, the data elucidate the mechanism of iron accumulation in CoA deficiency, highlighting the importance of mitochondrial iron deficiency in the pathogenesis of disease.

A c.726C>G (p.Tyr242Ter) nonsense mutation-associated with splicing alteration (NASA) of WDR45 gene underlies β-propeller protein-associated neurodegeneration (BPAN)

Neurodegeneration with brain iron accumulation (NBIA) is a clinically and genetically heterogeneous disease characterized by increased iron deposition in the basal ganglia and progressive degeneration of the nervous system in adulthood. However, in early childhood, there were no characteristic features to perform early diagnosis. In our study, a female child exhibited global developmental delay, intellectual disability, and febrile seizure without other distinct clinical phenotypes. Through whole exome sequencing (WES), a de novo nonsense mutation (c.726C > G, p. Tyr242Ter) of WDR45 gene was identified in this child. She was finally diagnosed as β-propeller protein-associated neurodegeneration (BPAN), one of the recently identified subtypes of NBIA. This mutation could act as a premature stop codon (PSC) which rendered the mutated transcripts to be degraded by nonsense-mediated mRNA decay (NMD), leading to decreased levels of PSC-containing mRNAs. Additionally, through mini-gene splicing assays, this mutation could result in an unprecedented novel transcript with the exon 9 of WDR45 excluded by nonsense-associated splicing alteration (NASA). Transcriptome sequencing (RNA-seq) on total RNAs from PBMCs of the trio revealed three types of alternative splicing events in the patient. Further research implied that downregulation of iron transport genes (TFRC, TFR2, SCARA5) might be the underlying mechanism for the iron accumulation in patients with deficient WDR45. This is the first report about NASA happening in WDR45. It implies that nonsense mutations approximal to splicing sites could affect the disease pathogenesis through more than one molecular mechanism and should be taken into consideration when conducting genetic counseling.

Trace Elements in Alzheimer's Disease and Dementia: The Current State of Knowledge

Changes in trace element concentrations are being wildly considered when it comes to neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease. This study aims to present the role that trace elements play in the central nervous system. Moreover, we reviewed the mechanisms involved in their neurotoxicity. Low zinc concentrations, as well as high levels of copper, manganese, and iron, activate the signalling pathways of the inflammatory, oxidative and nitrosative stress response. Neurodegeneration occurs due to the association between metals and proteins, which is then followed by aggregate formation, mitochondrial disorder, and, ultimately, cell death. In Alzheimer's disease, low Zn levels suppress the neurotoxicity induced by β-amyloid through the selective precipitation of aggregation intermediates. High concentrations of copper, iron and manganese cause the aggregation of intracellular α-synuclein, which results in synaptic dysfunction and axonal transport disruption. Parkinson's disease is caused by the accumulation of Fe in the midbrain dopaminergic nucleus, and the pathogenesis of multiple sclerosis derives from Zn deficiency, leading to an imbalance between T cell functions. Aluminium disturbs the homeostasis of other metals through a rise in the production of oxygen reactive forms, which then leads to cellular death. Selenium, in association with iron, plays a distinct role in the process of ferroptosis. Outlining the influence that metals have on oxidoreduction processes is crucial to recognising the pathophysiology of neurodegenerative diseases and may provide possible new methods for both their avoidance and therapy.

Case of Hallervorden-Spatz Syndrome: A Tale of Twin Sisters

Hallervorden-Spatz syndrome, now known as pantothenate kinase-associated neurodegeneration (PKAN), is a rare autosomal recessive disorder that is characterized by cerebral iron deposition and leads to progressive extrapyramidal dysfunction and dementia. Most commonly seen in the first two decades of a person's life, it is a differential for patients presenting with atypical progressive extrapyramidal disorder and cognitive impairment. It is characterized by progressive degeneration of the basal ganglia, globus pallidus, and the reticular part of the substantia nigra due to iron accumulation. The characteristic MRI brain pattern of the disease shows the eye-of-the-tiger sign. We report cases of early onset PKAN in two sisters of the same family, in which diagnosis was based on clinical features, lab parameters, and MRI imaging findings. This report aims to differentiate PKAN from other static and progressive neurological illnesses.

Neurodegeneration with Brain Iron Accumulation Disorders and Retinal Neurovascular Structure

BACKGROUND

The unique neurovascular structure of the retina has provided an opportunity to observe brain pathology in many neurological disorders. However, such studies on neurodegeneration with brain iron accumulation (NBIA) disorders are lacking.

OBJECTIVES

To investigate NBIA's neurological and ophthalmological manifestations.

METHODS

This cross-sectional study was conducted on genetically confirmed NBIA patients and an age-gender-matched control group. The thickness of retinal layers, central choroidal thickness (CCT), and capillary plexus densities were measured by spectral domain-optical coherence tomography (SD-OCT) and OCT angiography, respectively. The patients also underwent funduscopy, electroretinography (ERG), visual evoked potential (VEP), and neurological examination (Pantothenate-Kinase Associated Neurodegeneration-Disease Rating Scale [PKAN-DRS]). The generalized estimating equation model was used to consider inter-eye correlations.

RESULTS

Seventy-four patients' and 80 controls' eyes were analyzed. Patients had significantly decreased visual acuity, reduced inner or outer sectors of almost all evaluated layers, increased CCT, and decreased vessel densities, with abnormal VEP and ERG in 32.4% and 45.9%, respectively. There were correlations between visual acuity and temporal peripapillary nerve fiber layer (positive) and between PKAN-DRS score and disease duration (negative), and scotopic b-wave amplitudes (positive). When considering only the PKAN eyes, ONL was among the significantly decreased retinal layers, with no differences in retinal vessel densities. Evidence of pachychoroid was only seen in patients with Kufor Rakeb syndrome.

CONCLUSION

Observing pathologic structural and functional neurovascular changes in NBIA patients may provide an opportunity to elucidate the underlying mechanisms and differential retinal biomarkers in NBIA subtypes in further investigations. © 2023 International Parkinson and Movement Disorder Society.

Pantothenate Kinase Activation Restores Brain Coenzyme A in a Mouse Model of Pantothenate Kinase-Associated Neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) is characterized by a motor disorder with combinations of dystonia, parkinsonism, and spasticity, leading to premature death. PKAN is caused by mutations in the PANK2 gene that result in loss or reduction of PANK2 protein function. PANK2 is one of three kinases that initiate and regulate coenzyme A biosynthesis from vitamin B5, and the ability of BBP-671, an allosteric activator of pantothenate kinases, to enter the brain and elevate coenzyme A was investigated. The metabolic stability, protein binding, and membrane permeability of BBP-671 all suggest that it has the physical properties required to cross the blood-brain barrier. BBP-671 was detected in plasma, liver, cerebrospinal fluid, and brain following oral administration in rodents, demonstrating the ability of BBP-671 to penetrate the brain. The pharmacokinetic and pharmacodynamic properties of orally administered BBP-671 evaluated in cannulated rats showed that coenzyme A (CoA) concentrations were elevated in blood, liver, and brain. BBP-671 elevation of whole-blood acetyl-CoA served as a peripheral pharmacodynamic marker and provided a suitable method to assess target engagement. BBP-671 treatment elevated brain coenzyme A concentrations and improved movement and body weight in a PKAN mouse model. Thus, BBP-671 crosses the blood-brain barrier to correct the brain CoA deficiency in a PKAN mouse model, resulting in improved locomotion and survival and providing a preclinical foundation for the development of BBP-671 as a potential treatment of PKAN. SIGNIFICANCE STATEMENT: The blood-brain barrier represents a major hurdle for drugs targeting brain metabolism. This work describes the pharmacokinetic/pharmacodynamic properties of BBP-671, a pantothenate kinase activator. BBP-671 crosses the blood-brain barrier to correct the neuron-specific coenzyme A (CoA) deficiency and improve motor function in a mouse model of pantothenate kinase-associated neurodegeneration. The central role of CoA and acetyl-CoA in intermediary metabolism suggests that pantothenate kinase activators may be useful in modifying neurological metabolic disorders.

Femur Fractures in 5 Individuals With Pantothenate Kinase-associated Neurodegeneration: The Role of Dystonia and Suggested Management

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare, neurodegenerative disorder that manifests with progressive loss of ambulation and refractory dystonia, especially in the early-onset classic form. This leads to osteopenia and stress on long bones, which pose an increased risk of atraumatic femur fractures. The purpose of this study is to describe the unique challenges in managing femur fractures in PKAN and the effect of disease manifestations on surgical outcomes.

METHODS

A retrospective case review was conducted on 5 patients (ages 10 to 20 y) with PKAN with a femur fracture requiring surgical intervention. Data regarding initial presentation, surgical treatment, complications, and outcomes were obtained.

RESULTS

All patients were non-ambulatory, with 4 of 5 patients sustaining an atraumatic femur fracture in the setting of dystonia episode. One patient had an additional contralateral acetabular fracture. Postoperatively, 4 of the 5 patients sustained orthopaedic complications requiring surgical revision, with 3 of these secondary to dystonia. Overall, 4 required prolonged hospitalization in the setting of refractory dystonia.

CONCLUSION

Femur fractures in PKAN present distinct challenges for successful outcomes. A rigid intramedullary rod with proximal and distal interlocking screws is most protective against surgical complications associated with refractory dystonia occurring during the postoperative period. Multidisciplinary planning for postoperative care is essential and may include aggressive sedation and pain management to decrease the risk of subsequent injuries or complications.

LEVEL OF EVIDENCE

Level IV.

Estimation of Ambulation and Survival in Neurodegeneration with Brain Iron Accumulation Disorders

BACKGROUND

Neurodegeneration with Brain Iron Accumulation (NBIA) disorder is a group of ultra-orphan hereditary diseases with very limited data on its course.

OBJECTIVES

To estimate the probability of preserving ambulatory ability and survival in NBIA.

METHODS

In this study, the electronic records of the demographic data and clinical assessments of NBIA patients from 2012 to 2023 were reviewed. The objectives of the study and factors impacting them were investigated by Kaplan-Meier and Cox regression methods.

RESULTS

One hundred and twenty-two genetically-confirmed NBIA patients consisting of nine subtypes were enrolled. Twenty-four and twenty-five cases were deceased and wheelchair-bound, with a mean disease duration of 11 ± 6.65 and 9.32 ± 5 years. The probability of preserving ambulation and survival was 42.9% in 9 years and 28.2% in 15 years for classical Pantothenate Kinase-Associated Neurodegeneration (PKAN, n = 18), 89.4% in 7 years and 84.7% in 9 years for atypical PKAN (n = 39), 23% in 18 years and 67.8% in 14 years for Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN, n = 23), 75% in 20 years and 36.5% in 33 years for Kufor Rakeb Syndrome (KRS, n = 17), respectively. The frequencies of rigidity, spasticity, and female gender were significantly higher in deceased cases compared to surviving patients. Spasticity was the only factor associated with death (P value = 0.03).

CONCLUSIONS

KRS had the best survival with the most extended ambulation period. The classical PKAN and MPAN cases had similar progression patterns to loss of ambulation ability, while MPAN patients had a slower progression to death. Spasticity was revealed to be the most determining factor for death.

Ataxic gait and dysarthria in a child: pantothenate kinase-associated neurodegeneration as a diagnosis

Pantothenate kinase-associated neurodegeneration (or previously known as Hallervorden-Spatz syndrome) is a very rare disorder that typically manifests in a child with neurological signs such as gait difficulties, dysarthria, and hyperreflexia, associated potentially with psychiatric symptoms such as cognitive decline. It demonstrates on MRI the typical 'eye of the tiger' appearance, which is due to gliosis and accumulation of iron in the globi pallidi. Other differentials can mimic this appearance on MRI, it is therefore important to search for the involvement of other basal ganglia nuclei and the cerebral cortex, and also to consider the clinical and biological context.

Treatment of Pantothenate-Kinase Neurodegeneration With Baclofen, Botulinum Toxin, and Deferiprone: A Case Report

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare autosomal recessive disorder characterized by progressive motor symptoms, such as dystonia and spasticity. Classical PKAN is the most common subtype of neurodegeneration with brain iron accumulation (NBIA). Currently, there is no established treatment for PKAN. However, baclofen and botulinum toxin have been reported to improve motor symptoms and ease care in these patients. Additionally, Deferiprone is a well-tolerated iron chelator that has been shown to be effective in reducing brain iron accumulation. In this case report, we present the case of a seven-year-old boy who presented to our ward with spastic gait and extrapyramidal signs. Brain magnetic resonance imaging was performed, which showed features of neurodegeneration secondary to brain iron accumulation with a specific appearance of the eye-of-the-tiger sign. Genetic testing was positive for a homozygous mutation in PANK2, and the diagnosis of early-stage classical PKAN was made. This case report highlights the potent efficacy of baclofen, botulinum toxin, and deferiprone in slowing down the disease progression at an early stage and improving the severity of symptoms.

Pantothenate Kinase-Associated Neurodegeneration (PKAN) With Concomitant Blepharospasm: Unveiling a Clinical Enigma

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare and complex neurodegenerative disorder. It occurs due to mutations in the sequencing of the PANK2 gene. Here, we describe the case of a 22-year-old male patient who presented with severe blepharospasm; he had abnormal facial distortions, shaky limbs, rigid muscles, and a slow pace of movement, making a diagnosis tricky. Accumulation of iron in excessive amounts in the basal ganglia, a part of the brain that governs movement, is linked to PKAN. In this case, the "eye of the tiger" indication, a distinctive pattern only seen by MRI, supported PKAN. The anticholinergic medications helped him alleviate his symptoms to some extent, but he still had some degree of impairment. This instance emphasizes the mysterious character of PKAN and the significance of keeping an eye out for unusual symptoms in neurodegenerative conditions. This case report emphasizes the significance of recognizing unexpected effects that brain disorders can have on people's lives and calls for increased clinician awareness and understanding.

Patient-Derived Cellular Models for Polytarget Precision Medicine in Pantothenate Kinase-Associated Neurodegeneration

The term neurodegeneration with brain iron accumulation (NBIA) brings together a broad set of progressive and disabling neurological genetic disorders in which iron is deposited preferentially in certain areas of the brain. Among NBIA disorders, the most frequent subtype is pantothenate kinase-associated neurodegeneration (PKAN) caused by pathologic variants in the PANK2 gene codifying the enzyme pantothenate kinase 2 (PANK2). To date, there are no effective treatments to stop the progression of these diseases. This review discusses the utility of patient-derived cell models as a valuable tool for the identification of pharmacological or natural compounds for implementing polytarget precision medicine in PKAN. Recently, several studies have described that PKAN patient-derived fibroblasts present the main pathological features associated with the disease including intracellular iron overload. Interestingly, treatment of mutant cell cultures with various supplements such as pantothenate, pantethine, vitamin E, omega 3, α-lipoic acid L-carnitine or thiamine, improved all pathophysiological alterations in PKAN fibroblasts with residual expression of the PANK2 enzyme. The information provided by pharmacological screenings in patient-derived cellular models can help optimize therapeutic strategies in individual PKAN patients.

Patient and caregiver experiences with pantothenate kinase-associated neurodegeneration (PKAN): results from a patient community survey

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare autosomal recessive genetic disorder of PANK2, which enables mitochondrial synthesis of coenzyme A. Its loss causes neurodegeneration with iron accumulation primarily in motor-related brain areas. Symptoms include dystonia, parkinsonism, and other disabilities. PKAN has been categorized as classic PKAN, with an age of onset ≤ 10 years, rapid progression, and early disability or death; and atypical PKAN, with later onset, slower progression, generally milder, and more diverse symptom manifestations. Available treatments are mostly palliative. Information on the lived experience of patients with PKAN and their caregivers or on community-level disease burden is limited. It is necessary to engage patients as partners to expand our understanding and improve clinical outcomes. This patient-oriented research study used multiple-choice and free-form question surveys distributed by patient organizations to collect information on the manifestations and disease burden of PKAN. It also assessed respondents' experiences and preferences with clinical research to inform future clinical trials.

RESULTS

The analysis included 166 surveys. Most respondents (87%) were parents of a patient with PKAN and 7% were patients, with 80% from Europe and North America. The study cohort included 85 patients with classic PKAN (mean ± SD age of onset 4.4 ± 2.79 years), 65 with atypical PKAN (13.8 ± 4.79 years), and 16 identified as "not sure". Respondents reported gait disturbances and dystonia most often in both groups, with 44% unable to walk. The classic PKAN group reported more speech, swallowing, and visual difficulties and more severe motor problems than the atypical PKAN group. Dystonia and speech/swallowing difficulties were reported as the most challenging symptoms. Most respondents reported using multiple medications, primarily anticonvulsants and antiparkinsonian drugs, and about half had participated in a clinical research study. Study participants reported the most difficulties with the physical exertion associated with imaging assessments and travel to assessment sites.

CONCLUSIONS

The survey results support the dichotomy between classic and atypical PKAN that extends beyond the age of onset. Inclusion of patients as clinical research partners shows promise as a pathway to improving clinical trials and providing more efficacious PKAN therapies.

Orthopaedic Eponyms: A Tool of the Past

Eponyms are commonplace in the medical vernacular, however, their use has become increasingly controversial amongst clinicians. Whilst some view them as an honour bestowed on those whose achievements deserve recognition, others see them as thwarted with problems due to confusion, imprecision and unwittingly applauding controversial figures. Nevertheless, the history and culture retained within eponyms define modern-day medicine. To identify current trends in understanding of eponyms, we presented a questionnaire of orthopaedic eponyms and their associated imaging to unspecialised trainees, specialist orthopaedic trainees, and qualified consultants. Eponymous terms were poorly understood at all levels of experience, with- third and fourth-year Orthopaedic trainees (specialist trainee years five and six (ST5/ST6)) being outperformed (22.3%) by non-specialist postgraduate doctors with two or more years of experience (foundation year two (F2) and core surgery year two (CT2)) (29.3%). Based on these trends we present a further narrative review of the challenges eponyms present, whilst justifying their continued use to acknowledge the origins of our discipline, from the favourable to shameful.

Drug Drop Test: How to Quickly Identify Potential Therapeutic Compounds for Mitochondrial Diseases Using Yeast Saccharomyces cerevisiae

Mitochondrial diseases (MDs) refer to a group of clinically and genetically heterogeneous pathologies characterized by defective mitochondrial function and energy production. Unfortunately, there is no effective treatment for most MDs, and current therapeutic management is limited to relieving symptoms. The yeast Saccharomyces cerevisiae has been efficiently used as a model organism to study mitochondria-related disorders thanks to its easy manipulation and well-known mitochondrial biogenesis and metabolism. It has been successfully exploited both to validate alleged pathogenic variants identified in patients and to discover potential beneficial molecules for their treatment. The so-called "drug drop test", a phenotype-based high-throughput screening, especially if coupled with a drug repurposing approach, allows the identification of molecules with high translational potential in a cost-effective and time-saving manner. In addition to drug identification, S. cerevisiae can be used to point out the drug's target or pathway. To date, drug drop tests have been successfully carried out for a variety of disease models, leading to very promising results. The most relevant aspect is that studies on more complex model organisms confirmed the effectiveness of the drugs, strengthening the results obtained in yeast and demonstrating the usefulness of this screening as a novel approach to revealing new therapeutic molecules for MDs.

Clinical, imaging and genetic profile of twenty-four patients with pantothenate kinase-associated neurodegeneration (PKAN)- A single centre study from India

INTRODUCTION

Pantothenate kinase-associated neurodegeneration (PKAN) is the most common "Neurodegeneration with Brain Iron Accumulation" disorder. This study aimed to study the clinical, radiological and genetic profiling of a large cohort of patients with PKAN.

METHODS

This is an ambispective hospital-based single centre study conducted at a tertiary care centre from India. After tabulating the clinical details, appropriate rating scales were applied followed by magnetic resonance imaging brain and exome sequencing. The segregation of the causal variants in the families were analysed using Sanger sequencing.

RESULTS

Twenty-four patients (14 males) with a median age at initial examination of 13 years (range: 4-54 years) and age at onset of 8 years (range: 0.5-40 years) were identified. Almost two-thirds (62%) had onset before 10 years. Difficulty walking was the most common presenting symptom (41.6%) and dystonia was the most common extrapyramidal phenomenology (100%) followed by parkinsonism (54.2%). Retinitis pigmentosa was present in 37.5% patients. MRI showed hypo intensity on T2 and SWI sequences in globus pallidus (100%), substantia nigra (70.8%) and red nucleus (12.5%). Eye-of-the-tiger sign was present in 95.8%. Biallelic variants in PANK2 gene was identified in all 20 patients who underwent genetic testing. Among the 18 unique variants identified in these 20 patients 10 were novel. Sanger sequencing confirmed the segregation of the mutation in the available family members.

CONCLUSIONS

Wide range of age at onset was noted. Dystonia at presentation, pathognomonic eye-of-tiger sign, and disease-causing variants in PANK2 gene were identified in nearly all patients. Ten novel variants were identified expanding the genotypic spectrum of PKAN.

Alpha-lipoic acid supplementation corrects pathological alterations in cellular models of pantothenate kinase-associated neurodegeneration with residual PANK2 expression levels

BACKGROUND

Neurodegeneration with brain iron accumulation (NBIA) disorders are a group of neurodegenerative diseases that have in common the accumulation of iron in the basal nuclei of the brain which are essential components of the extrapyramidal system. Frequent symptoms are progressive spasticity, dystonia, muscle rigidity, neuropsychiatric symptoms, and retinal degeneration or optic nerve atrophy. One of the most prevalent subtypes of NBIA is Pantothenate kinase-associated neurodegeneration (PKAN). It is caused by pathogenic variants in the gene of pantothenate kinase 2 (PANK2) which encodes the enzyme responsible for the first reaction on the coenzyme A (CoA) biosynthesis pathway. Thus, deficient PANK2 activity induces CoA deficiency as well as low expression levels of 4'-phosphopantetheinyl proteins which are essential for mitochondrial metabolism.

METHODS

This study is aimed at evaluating the role of alpha-lipoic acid (α-LA) in reversing the pathological alterations in fibroblasts and induced neurons derived from PKAN patients. Iron accumulation, lipid peroxidation, transcript and protein expression levels of PANK2, mitochondrial ACP (mtACP), 4''-phosphopantetheinyl and lipoylated proteins, as well as pyruvate dehydrogenase (PDH) and Complex I activity were examined.

RESULTS

Treatment with α-LA was able to correct all pathological alterations in responsive mutant fibroblasts with residual PANK2 enzyme expression. However, α-LA had no effect on mutant fibroblasts with truncated/incomplete protein expression. The positive effect of α-LA in particular pathogenic variants was also confirmed in induced neurons derived from mutant fibroblasts.

CONCLUSIONS

Our results suggest that α-LA treatment can increase the expression levels of PANK2 and reverse the mutant phenotype in PANK2 responsive pathogenic variants. The existence of residual enzyme expression in some affected individuals raises the possibility of treatment using high dose of α-LA.

Anesthetic management of deep brain stimulation in Hallervorden-Spatz syndrome: Surviving the "eye of the tiger"

Anesthetic management of dystonic patients with uncontrolled involuntary movements refractory to medical management is a challenge to neuroanaesthetists. According to some studies, the prevalence of Panthothenate Kinase Associated Neurodegeneration is 1 to 9/1,000,000. Report of Deep Brain Stimulation for Hallervorden-Spatz is extremely rare in literature. "Awake" bilateral electrode placement, with microelectrode recording (MER) and stimulation with a scalp nerve block, titrated conscious sedation with Monitored Anesthesia Care (MAC) is preferable. However, in those patients needing general anesthesia, a balanced anesthesia technique with careful selection and monitored titration of anesthetic drugs ensuring MERs for precise placement and stimulation of target nuclei along with adequate plane and depth of anesthesia and prevention of awareness are essentially the key factors in the anesthetic management. Surgery is the mainstay of the disease due to poor response to medical management. Multidisciplinary collaboration and cooperation among neurologists, neurosurgeons, neuroradiologists, and neuroanaesthesiologists are imperative to ensure good patient outcomes.

Study design challenges and strategies in clinical trials for rare diseases: Lessons learned from pantothenate kinase-associated neurodegeneration

Substantial challenges in study design and methodology exist during clinical trial development to examine treatment response in patients with a rare disease, especially those with predominant central nervous system involvement and heterogeneity in clinical manifestations and natural history. Here we discuss crucial decisions which may significantly impact success of the study, including patient selection and recruitment, identification and selection of endpoints, determination of the study duration, consideration of control groups including natural history controls, and selection of appropriate statistical analyses. We review strategies for the successful development of a clinical trial to evaluate treatment of a rare disease with a focus on inborn errors of metabolism (IEMs) that present with movement disorders. The strategies presented using pantothenate kinase-associated neurodegeneration (PKAN) as the rare disease example can be applied to other rare diseases, particularly IEMs with movement disorders (e.g., other neurodegeneration with brain iron accumulation disorders, lysosomal storage disorders). The significant challenges associated with designing a clinical trial in rare disease can sometimes be successfully met through strategic engagement with experts in the rare disease, seeking regulatory and biostatistical guidance, and early involvement of patients and families. In addition to these strategies, we discuss the urgent need for a paradigm shift within the regulatory processes to help accelerate medical product development and bring new innovations and advances to patients with rare neurodegenerative diseases who need them earlier in disease progression and prior to clinical manifestations.

PPAR Gamma Agonist Leriglitazone Recovers Alterations Due to Pank2-Deficiency in hiPS-Derived Astrocytes

The novel brain-penetrant peroxisome proliferator-activated receptor gamma agonist leriglitazone, previously validated for other rare neurodegenerative diseases, is a small molecule that acts as a regulator of mitochondrial function and exerts neuroprotective, anti-oxidative and anti-inflammatory effects. Herein, we tested whether leriglitazone can be effective in ameliorating the mitochondrial defects that characterize an hiPS-derived model of Pantothenate kinase-2 associated Neurodegeneration (PKAN). PKAN is caused by a genetic alteration in the mitochondrial enzyme pantothenate kinase-2, whose function is to catalyze the first reaction of the CoA biosynthetic pathway, and for which no effective cure is available. The PKAN hiPS-derived astrocytes are characterized by mitochondrial dysfunction, cytosolic iron deposition, oxidative stress and neurotoxicity. We monitored the effect of leriglitazone in comparison with CoA on hiPS-derived astrocytes from three healthy subjects and three PKAN patients. The treatment with leriglitazone did not affect the differentiation of the neuronal precursor cells into astrocytes, and it improved the viability of PKAN cells and their respiratory activity, while diminishing the iron accumulation similarly or even better than CoA. The data suggest that leriglitazone is well tolerated in this cellular model and could be considered a beneficial therapeutic approach in the treatment of PKAN.

Case report: Novel compound heterozygous variants in the PANK2 gene in a Chinese patient diagnosed with ASD and ADHD

The PANK2 gene, which encodes mitochondrial pantothenate kinase 2 protein, is the disease-causing gene for pantothenate kinase-associated neurodegeneration (PKAN). We report a case of atypical PKAN with autism-like symptoms presenting with speech difficulties, psychiatric symptoms, and mild developmental retardation. Magnetic resonance imaging (MRI) of the brain showed the typical "eye-of-the-tiger" sign. Whole-exon sequencing revealed PANK2 p.Ile501Asn/p.Thr498Ser compound heterozygous variants. Our study highlights the phenotypic heterogeneity of PKAN, which can be confused with autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) and requires careful clinical identification.

Typical pantothenate kinase-associated neurodegeneration caused by compound heterozygous mutations in PANK2 gene in a Chinese patient: a case report and literature review

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare genetic neurodegenerative disorder with brain iron accumulation characterized as dysarthria, spasticity, cognitive impairment, parkinsonism, and retinopathy. PKAN is caused by biallelic mutations in the mitochondrial pantothenate kinase 2 (PANK2) gene. Herein, we report a 4-year-old patient with PKAN from a Han Chinese family, who presented with developmental regression, progressive inability to walk, and limb tremors. Neuroimaging demonstrated "eye-of-the-tiger" sign. Whole exome sequencing (WES) identified compound heterozygous mutations of c.1213T>G (p.Tyr405Asp) and c.1502T>A (p.Ile501Asn) in PANK2 gene. In addition, a review of all known PANK2 variants observed in reported PKAN patients was conducted, to improve understanding of the genotype-phenotype associations that occur in PKAN patients.

PKAN pathogenesis and treatment

Studies aimed at supporting different treatment approaches for pantothenate kinase-associated neurodegeneration (PKAN) have revealed the complexity of coenzyme A (CoA) metabolism and the limits of our current knowledge about disease pathogenesis. Here we offer a foundation for critically evaluating the myriad approaches, argue for the importance of unbiased disease models, and highlight some of the outstanding questions that are central to our understanding and treating PKAN.

Never-homozygous genetic variants in healthy populations are potential recessive disease candidates

The rapid pace with which genetic variants are now being determined means there is a pressing need to understand how they affect biological systems. Variants from healthy individuals have previously been used to study blood groups or HLA diversity and to identify genes that can apparently be nonfunctional in healthy people. These studies and others have observed a lower than expected frequency of homozygous individuals for potentially deleterious alleles, which would suggest that several of these alleles can lead to recessive disorders. Here we exploited this principle to hunt for potential disease variants in genomes from healthy people. We identified at least 108 exclusively heterozygous variants with evidence for an impact on biological function. We discuss several examples of candidate variants/genes including CCDC8, PANK3, RHD and NLRP12. Overall, the results suggest there are many, comparatively frequent, potentially lethal or disease-causing variants lurking in healthy human populations.

Therapeutic approach with commercial supplements for pantothenate kinase-associated neurodegeneration with residual PANK2 expression levels

Background

Neurodegeneration with brain iron accumulation (NBIA) is a group of rare neurogenetic disorders frequently associated with iron accumulation in the basal nuclei of the brain characterized by progressive spasticity, dystonia, muscle rigidity, neuropsychiatric symptoms, and retinal degeneration or optic nerve atrophy. Pantothenate kinase-associated neurodegeneration (PKAN) is one of the most widespread NBIA subtypes. It is caused by mutations in the gene of pantothenate kinase 2 (PANK2) that result in dysfunction in PANK2 enzyme activity, with consequent deficiency of coenzyme A (CoA) biosynthesis, as well as low levels of essential metabolic intermediates such as 4′-phosphopantetheine, a necessary cofactor for essential cytosolic and mitochondrial proteins.

Methods

In this manuscript, we examined the therapeutic effectiveness of pantothenate, panthetine, antioxidants (vitamin E and omega 3) and mitochondrial function boosting supplements (L-carnitine and thiamine) in mutant PANK2 cells with residual expression levels.

Results

Commercial supplements, pantothenate, pantethine, vitamin E, omega 3, carnitine and thiamine were able to eliminate iron accumulation, increase PANK2, mtACP, and NFS1 expression levels and improve pathological alterations in mutant cells with residual PANK2 expression levels.

Conclusion

Our results suggest that several commercial compounds are indeed able to significantly correct the mutant phenotype in cellular models of PKAN. These compounds alone or in combinations are of common use in clinical practice and may be useful for the treatment of PKAN patients with residual enzyme expression levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02465-9.

Long-Term Neuroradiological and Clinical Evaluation of NBIA Patients Treated with a Deferiprone Based Iron-Chelation Therapy

Neurodegeneration with brain iron accumulation (NBIA) comprises various rare clinical entities with brain iron overload as a common feature. Magnetic resonance imaging (MRI) allows diagnosis of this condition, and genetic molecular testing can confirm the diagnosis to better understand the intracellular damage mechanism involved. NBIA groups disorders include: pantothenate kinase-associated neurodegeneration (PKAN), mutations in the gene encoding pantothenate kinase 2 (PANK2); neuroferritinopathy, mutations in the calcium-independent phospholipase A2 gene (PLA2G6); aceruloplasminemia; and other subtypes with no specific clinical or MRI specific patterns identified. There is no causal therapy, and only symptom treatments are available for this condition. Promising strategies include the use of deferiprone (DFP), an orally administered bidentate iron chelator with the ability to pass through the blood–brain barrier. This is a prospective study analysis with a mean follow-up time of 5.5 ± 2.3 years (min–max: 2.4–9.6 years) to define DFP (15 mg/kg bid)’s efficacy and safety in the continuous treatment of 10 NBIA patients through clinical and neuroradiological evaluation. Our results show the progressive decrease in the cerebral accumulation of iron evaluated by MRI and a substantial stability of the overall clinical neurological picture without a significant correlation between clinical and radiological findings. Complete ferrochelation throughout the day appears to be of fundamental importance considering that oxidative damage is generated, above, all by non-transferrin-bound iron (NTBI); thus, we hypothesize that a (TID) administration regimen of DFP might better apply its chelating properties over 24 h with the aim to also obtain clinical improvement beyond the neuroradiological improvement.

Long-Term Outcomes of Deep Brain Stimulation in Pantothenate Kinase-Associated Neurodegeneration-Related Dystonia

Objective

To investigate the long-term clinical outcomes of pallidal deep brain stimulation (GPi-DBS) in patients with pantothenate kinase-associated neurodegeneration (PKAN).

Methods

We reviewed the records of patients with genetically confirmed PKAN who received bilateral GPi-DBS for refractory dystonia and were clinically followed up for at least 2 years postoperatively at two centers in Korea. Pre- and postoperative Burke- Fahn-Marsden Dystonia Rating Scale motor subscale (BFMDRS-M) scores, disability subscale (BFMDRS-D) scores, and qualitative clinical information were prospectively collected. Descriptive analysis was performed for BFMDRS-M scores, BFMDRSD scores, and the orofacial, axial, and limb subscores of the BFMDRS-M at 6-12, 24-36, and 60-72 months postoperatively.

Results

Five classic-type, four atypical-type, and one unknown-type PKAN cases were identified. The mean preoperative BFMDRS-M score was 92.1 for the classic type and 38.5 for the atypical or unknown type, with a mean BFMDRS follow-up of 50.7 months and a clinical follow-up of 69.0 months. The mean improvements in BFMDRS-M score were 11.3%, 41.3%, and 30.5% at 6-12, 24-36, and 60-72 months, respectively. In four patients with full regular evaluations until 60-72 months, improvements in the orofacial, axial, and limb subscores persisted, but the disability scores worsened from 24-36 months post-operation compared to the baseline, mainly owing to the aggravation of eating and feeding disabilities.

Conclusion

The benefits of GPi-DBS on dystonia may persist for more than 5 years in PKAN. The effects on patients' subjective disability may have a shorter duration despite improvements in dystonia owing to the complex manifestations of PKAN.

Potpourri of retinopathies in rare eye disease - A case series

This case series describes the ocular and retinal manifestations of rare eye diseases in systemic syndromes. This observational case series consists of five patients with varied ophthalmic manifestations and documentation of imaging in rare pediatric and adult retinopathies. Two patients had Kearns Sayre syndrome (KSS) based on the classical triad of external ophthalmoplegia, pigmentary retinopathy, and onset before 20 years of age. In one patient of KSS, the mitochondrial retinopathy was seen in an asymmetric pattern, and the second patient presented with KSS after being mis-diagnosed as myasthenia gravis elsewhere. A case of Senior Loken syndrome in pediatric age is described in this series with varied ophthalmic manifestations ranging from retinitis pigmentosa to orbital abscess. This series also enlightens features of Hallervorden Spatz syndrome presenting with bull's eye maculopathy and a case of spino-cerebellar ataxia type 7 presenting with pigmentary retinopathy.

Bilateral and Symmetrical Lesions in the Basal Ganglia Associated With Metabolic Acidosis in a Patient With a History of Alcohol Addiction: A Case Report

Metabolic acidosis is defined as a pathologic process that, when unopposed, increases the concentration of hydrogen ions in the body and reduces the concentration of HCO3. Methanol poisoning is an important cause of metabolic acidosis. Methanol and ethylene glycol poisonings cause scores of fatal intoxications annually, and even relatively small ingestions of these alcohols can produce significant toxicity. Neuroimaging findings are very suggestive and help in the diagnosis even before the measurement of serum methanol (when available at the health service). Rapid recognition and early treatment, including alcohol dehydrogenase inhibition, are crucial. In this sense, some studies question that many intoxications by different chemical agents (in addition to methanol and ethylene glycol) generate a conglomeration of neuroimaging findings that summarily reflect the presence of metabolic acidosis. Therefore, in this article, we discuss the imaging findings of metabolic acidosis, methanol poisoning, and their main differential diagnoses in neuroimaging, directing earlier diagnostic reasoning in order to initiate the most appropriate treatment promptly.

PKAN hiPS-Derived Astrocytes Show Impairment of Endosomal Trafficking: A Potential Mechanism Underlying Iron Accumulation

PKAN disease is caused by mutations in the PANK2 gene, encoding the mitochondrial enzyme pantothenate kinase 2, catalyzing the first and key reaction in Coenzyme A (CoA) biosynthetic process. This disorder is characterized by progressive neurodegeneration and excessive iron deposition in the brain. The pathogenic mechanisms of PKAN are still unclear, and the available therapies are only symptomatic. Although iron accumulation is a hallmark of PKAN, its relationship with CoA dysfunction is not clear. We have previously developed hiPS-derived astrocytes from PKAN patients showing iron overload, thus recapitulating the human phenotype. In this work, we demonstrated that PKAN astrocytes presented an increase in transferrin uptake, a key route for cellular iron intake via transferrin receptor-mediated endocytosis of transferrin-bound iron. Investigation of constitutive exo-endocytosis and vesicular dynamics, exploiting the activity-enriching biosensor SynaptoZip, led to the finding of a general impairment in the constitutive endosomal trafficking in PKAN astrocytes. CoA and 4-phenylbutyric acid treatments were found to be effective in partially rescuing the aberrant vesicular behavior and iron intake. Our results demonstrate that the impairment of CoA biosynthesis could interfere with pivotal intracellular mechanisms involved in membrane fusions and vesicular trafficking, leading to an aberrant transferrin receptor-mediated iron uptake.

Acanthocytes Identified in Huntington’s Disease

Background

Neuroacanthocytosis (NA) and Huntington’s disease (HD) are neurodegenerative conditions that share clinical symptoms and imaging findings, despite their distinct genetic etiologies. Usually, the presence of acanthocytes can help narrow the differential diagnosis of a familial choreiform disorder, as the diagnosis of NA syndrome is supported by the presence of acanthocytes in peripheral blood. In this study, we demonstrate four patients who present with HD and acanthocytosis.

Methods

We retrieved the data of 40 HD patients with fresh peripheral blood screened for erythrocytes in our hospital from 2014 to 2022. Of these 40 patients, four patients with acanthocytes were recruited for this study. Patients’ investigations included clinical and laboratory studies, HTT gene sequencing, and whole-exome sequencing. Fresh peripheral blood was screened for erythrocytes by scanning electron microscopy.

Results

The four adult patients were Han Chinese and unrelated. The age ranged from 45 to 61 years, with a disease duration of 4–10 years. The main neurological features at diagnosis included progressive involuntary movements, psychiatric changes, and dementia. Genetic analysis showed an expansion at the HTT gene. The mean proportion of acanthocytes was mild (6–10%) elevated in patient one and high (>20%) elevated in patients 2–4 by scanning electron microscopy examination.

Conclusion

Our study illustrates that HD can combine with acanthocytosis, which may expand the clinical phenotype. Even though the primary gene defect appears to be predominately directed at the brain, a peripheral defect can be seen in HD. Our study highlights the complexity and diversity of HD.

Pantothenate kinase 2 interacts with PINK1 to regulate mitochondrial quality control via acetyl-CoA metabolism

Human neurodegenerative disorders often exhibit similar pathologies, suggesting a shared aetiology. Key pathological features of Parkinson's disease (PD) are also observed in other neurodegenerative diseases. Pantothenate Kinase-Associated Neurodegeneration (PKAN) is caused by mutations in the human PANK2 gene, which catalyzes the initial step of de novo CoA synthesis. Here, we show that fumble (fbl), the human PANK2 homolog in Drosophila, interacts with PINK1 genetically. fbl and PINK1 mutants display similar mitochondrial abnormalities, and overexpression of mitochondrial Fbl rescues PINK1 loss-of-function (LOF) defects. Dietary vitamin B5 derivatives effectively rescue CoA/acetyl-CoA levels and mitochondrial function, reversing the PINK1 deficiency phenotype. Mechanistically, Fbl regulates Ref(2)P (p62/SQSTM1 homolog) by acetylation to promote mitophagy, whereas PINK1 regulates fbl translation by anchoring mRNA molecules to the outer mitochondrial membrane. In conclusion, Fbl (or PANK2) acts downstream of PINK1, regulating CoA/acetyl-CoA metabolism to promote mitophagy, uncovering a potential therapeutic intervention strategy in PD treatment.

Cerebral and cerebellar white matter tract alterations in patients with Pantothenate Kinase-Associated Neurodegeneration (PKAN)

BACKGROUND

To examine structural connectivity of white matter tracts in patients with Pantothenate Kinase-Associated Neurodegeneration (PKAN) dystonia and identify those ones which correlate negatively to severity of symptoms.

METHODS

In a group of 41 patients suffering from PKAN dystonia and an age- and gender-matched control group, white matter tractography was carried out, based on diffusion tensor imaging magnetic resonance data. Postprocessing included assessment of Quantitative Anisotropy (QA) using q-space diffeomorphic reconstruction in order to reduce influence of iron accumulation in globus pallidus of patients.

RESULTS

Whole brain tractography presented significantly reduced QA values in patients (0.282 ± 0.056, as compared to controls (0.325 ± 0.046, p < 0.001). 9 fiber clusters of tracts correlated negatively to the dystonia score of patients: the middle cerebellar peduncle and the tracts of both cerebellar hemispheres as well as corpus callosum, forceps minor, the superior cortico-striate tracts and the superior thalamic radiations of both cerebral hemispheres (False Discovery Rate FDR = 0.041).

CONCLUSION

The finding of a reduced global structural connectivity within the white matter and of negative correlation of motor system-related tracts, mainly those between the basal ganglia, cortical areas and the cerebellum, fits well to the concept of a general functional disturbance of the motor system in PKAN.

Novel PANK2 Mutations in Patients With Pantothenate Kinase-Associated Neurodegeneration and the Genotype–Phenotype Correlation

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare genetic disorder caused by mutations in the mitochondrial pantothenate kinase 2 (PANK2) gene and displays an inherited autosomal recessive pattern. In this study, we identified eight PANK2 mutations, including three novel mutations (c.1103A &gt; G/p.D368G, c.1696C &gt; G/p.L566V, and c.1470delC/p.R490fs494X), in seven unrelated families with PKAN. All the patients showed an eye-of-the-tiger sign on the MRI, six of seven patients had dystonia, and two of seven patients had Parkinsonism. Biallelic mutations of PANK2 decreased PANK2 protein expression and reduced mitochondrial membrane potential in human embryonic kidney (HEK) 293T cells. The biallelic mutations from patients with early-onset PKAN, a severity phenotype, showed decreased mitochondrial membrane potential more than that from late-onset patients. We systematically reviewed all the reported patients with PKAN with PANK2 mutations. The results indicated that the early-onset patients carried a significantly higher frequency of biallelic loss-of-function (LoF) mutations compared to late-onset patients. In general, patients with LoF mutations showed more severe phenotypes, including earlier onset age and loss of gait. Although there was no significant difference in the frequency of biallelic missense mutations between the early-onset and late-onset patients, we found that patients with missense mutations in the mitochondrial trafficking domain (transit peptide/mitochondrial domain) of PANK2 exhibited the earliest onset age when compared to patients with mutations in the other two domains. Taken together, this study reports three novel mutations and indicates a correlation between the phenotype and mitochondrial dysfunction. This provides new insight for evaluating the clinical severity of patients based on the degree of mitochondrial dysfunction and suggests genetic counseling not just generalized identification of mutated PANK2 in clinics.

Deep Brain Stimulation (DBS) with Subthalamic Nucleus (STN) as Target for Pediatric Patients with PKAN

OBJECT

Dystonia in Pantothenate Kinase-Associated Neurodegeneration(PKAN) is progressive despite medication. Deep brain stimulation(DBS) was reported to effectively provide symptom relief. No consensus exists in candidate and target selection for DBS. We aim to demonstrate effectiveness of subthalamic DBS(STN-DBS) placement in pediatric PKAN patients.

METHODS

We reviewed consecutive series of pediatric patients diagnosed with PKAN and treated with STN-DBS from 2016-2019 in our institution. Each case was described in detail. Preoperative and postoperative Burke-Fahn-Marsden Dystonia Rating Scale(BFMDRS) were assessed to evaluate functional improvement at follow-up.

RESULTS

Seven pediatric patients were included. Mean age of initial onset was 0.6±0.5 years and presentation to clinics was 6.6±1.3 years. Mean preoperative BFMDRS was 73.3±3.5. Following STN-DBS, for mean follow-up duration of 13.0±10.7 months, mean BFMDRS was 37.3±12.6, translating to score improvement of 36.0±12.9(p<0.001) and percentage improvement of 49.0±18.0%.

CONCLUSIONS

This case series demonstrated that STN-DBS is an effective symptom-based treatment for pediatric PKAN patients.

Genetic mutation spectrum of pantothenate kinase-associated neurodegeneration expanded by breakpoint sequencing in pantothenate kinase 2 gene

BACKGROUND

Neurodegeneration with brain iron accumulation describes a group of rare heterogeneous progressive neurodegenerative disorders characterized by excessive iron accumulation in the basal ganglia region. Pantothenate kinase-associated neurodegeneration (PKAN) is a major form of this disease.

RESULTS

A total of 7 unrelated patients were diagnosed with PKAN in a single tertiary center from August 2009 to February 2018. Ten variants in PANK2 including three novel sequence variants and one large exonic deletion were detected. Sequencing of the breakpoint was performed to predict the mechanism of large deletion and AluSx3 and AluSz6 were found with approximately 97.3% sequence homology.

CONCLUSION

The findings support the disease-causing role of PANK2 and indicate the possibility that exonic deletion of PANK2 found in PKAN is mediated through Alu-mediated homologous recombination.

Lifetime risk of autosomal recessive neurodegeneration with brain iron accumulation (NBIA) disorders calculated from genetic databases

Background

Neurodegeneration with brain iron accumulation (NBIA) are a group of clinically and genetically heterogeneous diseases characterized by iron overload in basal ganglia and progressive neurodegeneration. Little is known about the epidemiology of NBIA disorders. In the absence of large-scale population-based studies, obtaining reliable epidemiological data requires innovative approaches.

Methods

All pathogenic variants were collected from the 13 genes associated with autosomal recessive NBIA (PLA2G6, PANK2, COASY, ATP13A2, CP, AP4M1, FA2H, CRAT, SCP2, C19orf12, DCAF17, GTPBP2, REPS1). The allele frequencies of these disease-causing variants were assessed in exome/genome collections: the Genome Aggregation Database (gnomAD) and our in-house database. Lifetime risks were calculated from the sum of allele frequencies in the respective genes under assumption of Hardy-Weinberg equilibrium.

Findings

The combined estimated lifetime risk of all 13 investigated NBIA disorders is 0.88 (95% confidence interval 0.70–1.10) per 100,000 based on the global gnomAD dataset (n = 282,912 alleles), 0.92 (0.65–1.29) per 100,000 in the European gnomAD dataset (n = 129,206), and 0.90 (0.48–1.62) per 100,000 in our in-house database (n = 44,324). Individually, the highest lifetime risks (>0.15 per 100,000) are found for disorders caused by variants in PLA2G6, PANK2 and COASY.

Interpretation

This population-genetic estimation on lifetime risks of recessive NBIA disorders reveals frequencies far exceeding previous population-based numbers. Importantly, our approach represents lifetime risks from conception, thus including prenatal deaths. Understanding the true lifetime risk of NBIA disorders is important in estimating disease burden, allocating resources and targeting specific interventions.

Massive iron accumulation in PKAN-derived neurons and astrocytes: light on the human pathological phenotype

Neurodegeneration associated with defective pantothenate kinase-2 (PKAN) is an early-onset monogenic autosomal-recessive disorder. The hallmark of the disease is the massive accumulation of iron in the globus pallidus brain region of patients. PKAN is caused by mutations in the PANK2 gene encoding the mitochondrial enzyme pantothenate kinase-2, whose function is to catalyze the first reaction of the CoA biosynthetic pathway. To date, the way in which this alteration leads to brain iron accumulation has not been elucidated. Starting from previously obtained hiPS clones, we set up a differentiation protocol able to generate inhibitory neurons. We obtained striatal-like medium spiny neurons composed of approximately 70–80% GABAergic neurons and 10–20% glial cells. Within this mixed population, we detected iron deposition in both PKAN cell types, however, the viability of PKAN GABAergic neurons was strongly affected. CoA treatment was able to reduce cell death and, notably, iron overload. Further differentiation of hiPS clones in a pure population of astrocytes showed particularly evident iron accumulation, with approximately 50% of cells positive for Perls staining. The analysis of these PKAN astrocytes indicated alterations in iron metabolism, mitochondrial morphology, respiratory activity, and oxidative status. Moreover, PKAN astrocytes showed signs of ferroptosis and were prone to developing a stellate phenotype, thus gaining neurotoxic features. This characteristic was confirmed in iPS-derived astrocyte and glutamatergic neuron cocultures, in which PKAN glutamatergic neurons were less viable in the presence of PKAN astrocytes. This newly generated astrocyte model is the first in vitro disease model recapitulating the human phenotype and can be exploited to deeply clarify the pathogenetic mechanisms underlying the disease.

Clinical and Molecular Correlates of Abnormal Changes in the Cerebellum and Globus Pallidus in Fragile X Premutation

BACKGROUND

Fragile X premutation carriers (55-200 CGG triplets) may develop a progressive neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS), after the age of 50. The neuroradiologic markers of FXTAS are hyperintense T2-signals in the middle cerebellar peduncle-the MCP sign. We recently noticed abnormal T2-signals in the globus pallidus in male premutation carriers and controls but the prevalence and clinical significance were unknown.

METHODS

We estimated the prevalence of the MCP sign and pallidal T2-abnormalities in 230 male premutation carriers and 144 controls (aged 8-86), and examined the associations with FXTAS symptoms, CGG repeat length, and iron content in the cerebellar dentate nucleus and globus pallidus.

RESULTS

Among participants aged ≥45 years (175 premutation carriers and 82 controls), MCP sign was observed only in premutation carriers (52 vs. 0%) whereas the prevalence of pallidal T2-abnormalities approached significance in premutation carriers compared with controls after age-adjustment (25.1 vs. 13.4%, p = 0.069). MCP sign was associated with impaired motor and executive functioning, and the additional presence of pallidal T2-abnormalities was associated with greater impaired executive functioning. Among premutation carriers, significant iron accumulation was observed in the dentate nucleus, and neither pallidal or MCP T2-abnormalities affected measures of the dentate nucleus. While the MCP sign was associated with CGG repeat length >75 and dentate nucleus volume correlated negatively with CGG repeat length, pallidal T2-abnormalities did not correlate with CGG repeat length. However, pallidal signal changes were associated with age-related accelerated iron depletion and variability and having both MCP and pallidal signs further increased iron variability in the globus pallidus.

CONCLUSIONS

Only the MCP sign, not pallidal abnormalities, revealed independent associations with motor and cognitive impairment; however, the occurrence of combined MCP and pallidal T2-abnormalities may present a risk for greater cognitive impairment and increased iron variability in the globus pallidus.

Neuropsychological profile associated to PKAN in its initial phase: a case series report

Pantothenase kinase-associated neurodegeneration (PKAN) is characterized by an abnormal accumulation of iron in basal ganglia and progressing varied extrapyramidal clinical symptoms. There are few studies on the cognitive symptoms and their development. The aim of this study is to explore the neuropsychological profile of PKAN patients in the initial stages of the disorder, when there are relatively fewer motor limitations. we present a full neuropsychological examination of three female cases (two early and one late onset). perception and spatial cognition were within normal range. Performance on other tasks were mixed, except for primary impairments in inhibition, flexibility, and cognitive fluency, which were consistent across cases. unlike most previous studies which report adults with major motor impairment, we present cases of young participants with minor motor difficulties. The results of the neuropsychological assessment - potentially less confounded by poor motor functioning during examination - are compatible with impairments in the fronto-subcortical circuits in the early phases of the disease. This could explain frequent misdiagnoses (e.g., with attention deficit hyperactivity disorder) in initial referrals.

Towards Precision Therapies for Inherited Disorders of Neurodegeneration with Brain Iron Accumulation

Background:

Neurodegeneration with brain iron accumulation (NBIA) disorders comprise a group of rare but devastating inherited neurological diseases with unifying features of progressive cognitive and motor decline, and increased iron deposition in the basal ganglia. Although at present there are no proven disease-modifying treatments, the severe nature of these monogenic disorders lends to consideration of personalized medicine strategies, including targeted gene therapy. In this review we summarize the progress and future direction towards precision therapies for NBIA disorders.

Methods:

This review considered all relevant publications up to April 2021 using a systematic search strategy of PubMed and clinical trials databases.

Results:

We review what is currently known about the underlying pathophysiology of NBIA disorders, common NBIA disease pathways, and how this knowledge has influenced current management strategies and clinical trial design. The safety profile, efficacy and clinical outcome of clinical studies are reviewed. Furthermore, the potential for future therapeutic approaches is also discussed.

Discussion:

Therapeutic options in NBIAs remain very limited, with no proven disease-modifying treatments at present. However, a number of different approaches are currently under development with increasing focus on targeted precision therapies. Recent advances in the field give hope that novel strategies, such as gene therapy, gene editing and substrate replacement therapies are both scientifically and financially feasible for these conditions.

Highlights

This article provides an up-to-date review of the current literature about Neurodegeneration with Brain Iron Accumulation (NBIA), with a focus on disease pathophysiology, current and previously trialed therapies, and future treatments in development, including consideration of potential genetic therapy approaches.

An Eye on Movement Disorders

Eye disorders spanning a range of ocular tissue are common in patients with movement disorders. Highlighting these ocular manifestations will benefit patients and may even aid in diagnosis. In this educational review we outline the anatomy and function of the ocular tissues with a focus on the tissues most affected in movement disorders. We review the movement disorders associated with ocular pathology and where possible explore the underlying cellular basis thought to be driving the pathology and provide a brief overview of ophthalmic investigations available to the neurologist. This review does not cover intracranial primary visual pathways, higher visual function, or the ocular motor system.

Neurodegeneration with brain iron accumulation: Characterization of clinical, radiological, and genetic features of pediatric patients from Southern India

BACKGROUND

Neurodegeneration with brain iron accumulation (NBIA) is a group of rare inherited neurodegenerative disorders. Ten types of NBIA are known. Studies reporting various NBIA subtypes together are few. This study was aimed at describing clinical features, neuroimaging findings, and genetic mutations of different NBIA group disorders.

METHODS

Clinical, radiological, and genetic data of patients diagnosed with NBIA in a tertiary care centre in Southern India from 2014 to 2020 was retrospectively collected and analysed.

RESULTS

In our cohort of 27 cases, PLA2G6-associated neurodegeneration (PLAN) was most common (n = 13) followed by Pantothenate kinase-associated neurodegeneration (PKAN) (n = 9). We had 2 cases each of Mitochondrial membrane-associated neurodegeneration (MPAN) and Beta-propeller protein- associated neurodegeneration (BPAN) and 1 case of Kufor-Rakeb Syndrome (KRS). Walking difficulty was the presenting complaint in all PKAN cases, whereas the presentation in PLAN was that of development regression with onset at a mean age of 2 years. Overall, 50% patients of them presented with development regression and one-third had epilepsy. Presence of pyramidal signs was most common examination feature (89%) followed by one or more eye findings (81%) and movement disorders (50%). Neuroimaging was abnormal in 24/27 cases and cerebellar atrophy was the commonest finding (52%) followed by globus pallidus hypointensities (44%).

CONCLUSIONS

One should have a high index of clinical suspicion for the diagnosis of NBIA in children presenting with neuroregression and vision abnormalities in presence of pyramidal signs or movement disorders. Neuroimaging and ophthalmological evaluation provide important clues to diagnosis in NBIA syndromes.

Coenzyme a Biochemistry: From Neurodevelopment to Neurodegeneration

Coenzyme A (CoA) is an essential cofactor in all living organisms. It is involved in a large number of biochemical processes functioning either as an activator of molecules with carbonyl groups or as a carrier of acyl moieties. Together with its thioester derivatives, it plays a central role in cell metabolism, post-translational modification, and gene expression. Furthermore, recent studies revealed a role for CoA in the redox regulation by the S-thiolation of cysteine residues in cellular proteins. The intracellular concentration and distribution in different cellular compartments of CoA and its derivatives are controlled by several extracellular stimuli such as nutrients, hormones, metabolites, and cellular stresses. Perturbations of the biosynthesis and homeostasis of CoA and/or acyl-CoA are connected with several pathological conditions, including cancer, myopathies, and cardiomyopathies. In the most recent years, defects in genes involved in CoA production and distribution have been found in patients affected by rare forms of neurodegenerative and neurodevelopmental disorders. In this review, we will summarize the most relevant aspects of CoA cellular metabolism, their role in the pathogenesis of selected neurodevelopmental and neurodegenerative disorders, and recent advancements in the search for therapeutic approaches for such diseases.

Atypical pantothenate kinase-associated neurodegeneration with variable phenotypes in an Egyptian family

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare hereditary neurodegenerative disease characterized by an accumulation of iron within the brain. In the present report, we describe a family with 4 affected siblings presenting with variable clinical manifestations, e.g., parkinsonian features, dystonia and slow disease progression over 5 years. Exome sequencing revealed a causative variant in the pantothenate kinase 2 gene (PANK2). Variant NM_024960.6:c.710C > T was homozygous in all affected subjects. Our report describes the first genetically confirmed cases of PKAN in the Egyptian population. Studying genetics of neurodegenerative diseases in different ethnicities is very important for determining clinical phenotypes and understanding pathomechanisms of these diseases.

Fosmetpantotenate Randomized Controlled Trial in Pantothenate Kinase-Associated Neurodegeneration

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) currently has no approved treatments.

OBJECTIVES

The Fosmetpantotenate Replacement Therapy pivotal trial examined whether treatment with fosmetpantotenate improves PKAN symptoms and stabilizes disease progression.

METHODS

This randomized, double-blind, placebo-controlled, multicenter study evaluated fosmetpantotenate, 300 mg oral dose three times daily, versus placebo over a 24-week double-blind period. Patients with pathogenic variants of PANK2, aged 6 to 65 years, with a score ≥6 on the PKAN-Activities of Daily Living (PKAN-ADL) scale were enrolled. Patients were randomized to active (fosmetpantotenate) or placebo treatment, stratified by weight and age. The primary efficacy endpoint was change from baseline at week 24 in PKAN-ADL.

RESULTS

Between July 23, 2017, and December 18, 2018, 84 patients were randomized (fosmetpantotenate: n = 41; placebo: n = 43); all 84 patients were included in the analyses. Six patients in the placebo group discontinued treatment; two had worsening dystonia, two had poor compliance, and two died of PKAN-related complications (aspiration during feeding and disease progression with respiratory failure, respectively). Fosmetpantotenate and placebo group PKAN-ADL mean (standard deviation) scores were 28.2 (11.4) and 27.4 (11.5) at baseline, respectively, and were 26.9 (12.5) and 24.5 (11.8) at week 24, respectively. The difference in least square mean (95% confidence interval) at week 24 between fosmetpantotenate and placebo was -0.09 (-1.69 to 1.51; P = 0.9115). The overall incidence of treatment-emergent serious adverse events was similar in the fosmetpantotenate (8/41; 19.5%) and placebo (6/43; 14.0%) groups.

CONCLUSIONS

Treatment with fosmetpantotenate was safe but did not improve function assessed by the PKAN-ADL in patients with PKAN. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.