Neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) describes a group of progressive extrapyramidal disorders with radiographic evidence of focal iron accumulation in the brain, usually in the basal ganglia. Patients previously diagnosed with Hallervorden-Spatz syndrome fall into this category. Mutations in the PANK2 gene account for the majority of NBIA cases and cause an autosomal recessive inborn error of coenzyme A metabolism called pantothenate kinase-associated neurodegeneration (PKAN). PKAN is characterized by dystonia and pigmentary retinopathy in children or speech and neuropsychiatric disorders in adults. In addition, a specific pattern on brain MRI, called the eye-of-the-tiger sign, is virtually pathognomonic for the disease. Pantothenate kinase is essential to coenzyme A biosynthesis, and the PANK2 protein is targeted to the mitochondria. Hypotheses of PKAN pathogenesis are based on the predictions of tissue-specific coenzyme A deficiency and the accumulation of cysteine-containing substrates. Identification of the major NBIA gene has led to more accurate clinical delineation of the diseases that comprise this group, a molecular diagnostic test for PKAN, and hypotheses for treatment.     

Indian‐subcontinent NBIA: Unusual phenotypes,novel PANK2 mutations,and undetermined genetic forms

Neurodegeneration with brain iron accumulation (NBIA) is etiologically, clinically, and by imaging a heterogeneous group including NBIA types 1 [pantothenate kinase‐associated neurodegeneration (PKAN)] and 2 (PLA2G6‐associated neurodegeneration), neuroferritinopathy, and aceruloplasminaemia. Data on genetically defined Indian‐subcontinent NBIA cases are limited. We report 6 patients from the Indian‐subcontinent with a movement disorder and MRI basal ganglia iron deposition, compatible with diagnosis of an NBIA syndrome. All patients were screened for abnormalities in serum ceruloplasmin and ferritin levels and mutations in NBIA‐associated genes [pantothenate kinase 2 (PANK2), PLA2G6 and ferritin light chain (exon 4)]. We present clinical, imaging and genetic data correlating phenotype–genotype relations. Four patients carried PANK2 mutations, two of these were novel. The clinical phenotype was mainly dystonic with generalized dystonia and marked orobulbar features in the 4 adolescent‐onset cases. One of the four had a late‐onset (age 37) unilateral jerky postural tremor. His mutation, c.1379C>T, appears associated with a milder phenotype. Interestingly, he developed the eye‐of‐the‐tiger sign only 10 years after onset. Two of the six presented with adult‐onset levodopa (L ‐dopa)‐responsive asymmetric re‐emergent rest tremor, developing L ‐dopa‐induced dyskinesias, and good benefit to deep brain stimulation (in one), thus resembling Parkinson's disease (PD). Both had an eye‐of‐the‐tiger sign on MRI but were negative for known NBIA‐associated genes, suggesting the existence of further genetic or sporadic forms of NBIA syndromes. In conclusion, genetically determined NBIA cases from the Indian subcontinent suggest presence of unusual phenotypes of PANK2 and novel mutations. The phenotype of NBIA of unknown cause includes a PD‐like presentation. © 2010 Movement Disorder Society     

泛酸激酶相关性神经变性疾病遗传学与临床研究进展

泛酸激酶相关性神经变性疾病是脑组织铁沉积性神经变性(NBIA,曾称为Hallervorden-Spatz综合征)疾病的主要发病类型之一,系由泛酸激酶2(PANK2)基因突变所导致的常染色体隐性遗传性疾病。PANK2基因突变可干扰PANK2蛋白表达水平和催化活性,以及线粒体靶蛋白的成熟与稳定性,引起神经元线粒体脂类代谢异常改变,导致脑组织铁沉积性神经变性疾病。本文对该病分子遗传学机制及其与临床表型和影像学特征相关的研究成果和进展进行概述。     

Clinical heterogeneity of neurodegeneration with brain iron accumulation (Hallervorden-Spatz syndrome) and pantothenate kinase-associated neurodegeneration.

Hallervorden Spatz syndrome (HSS), also referred to as neurodegeneration with brain iron accumulation (NBIA), is a rare inherited neurodegenerative disorder with childhood, adolescent, or adult onset. Patients with HSS/NBIA have a combination of motor symptoms in the form of dystonia, parkinsonism, choreoathetosis, corticospinal tract involvement, optic atrophy, pigmentary retinopathy, and cognitive impairment. After the recent identification of mutations in the PANK2 gene on chromosome 20p12.3-p13 in some patients with the HSS/NBIA phenotype, the term pantothenate kinase-associated neurodegeneration (PKAN) has been proposed for this group of disorders. To characterize clinically and genetically HSS/NBIA, we reviewed 34 affected individuals from 10 different families, who satisfied the inclusion criteria for NBIA. Relatives of patients who had clinical, magnetic resonance imaging (MRI), or pathological findings of NBIA were included in the study. Four patients were found to have mutations in the pantothenate kinase 2 (PANK2) gene. We compared the clinical features and MRI findings of those with and without PANK2 mutations. The presence of mutation in the PANK2 gene is associated with younger age at onset and a higher frequency of dystonia, dysarthria, intellectual impairment, and gait disturbance. Parkinsonism is seen predominantly in adult-onset patients whereas dystonia seems more frequent in the earlier-onset cases. The phenotypic heterogeneity observed in our patients supports the notion of genetic heterogeneity in the HSS/NBIA syndrome.     

Atypical pantothenate kinase-associated neurodegeneration with PANK2 mutations : clinical description and a review of the literature

ABSTRACT

Panthothenate kinase-associated neurodegeneration (PKAN) is arare neurodegeneration caused by mutations in the pantothenate kinase (PANK2) gene, which is located on chromosome 20p13. These mutations result in iron accumulation in the brain basal ganglia leading to parkinsonism, dysarthria, spasticity, cognitive impairment, and retinopathy. Herein, we report acase of adult-onset PKAN who presented with young-onset action tremor, bradykinesia, dysarthria, and bilateral interossei atrophy. Neuroimaging demonstrated “eye-of-the-tiger signs”. Through analyzing PANK2 gene, PANK2 NM_153638:c.1133A>G (p.Asp378 Gly) and PANK2 NM_153638:c.1502 T > A (p.lle501Asn), were detected. In addition, we reviewed the clinical and genetic features and therapeutic strategies for patients with PKAN.     

Novel compound heterozygous PANK2 gene mutations in a Chinese patient with atypical pantothenate kinase-associated neurodegeneration

Abstract

Aim: Pantothenate-kinase-associated neurodegeneration (PKAN), which is characterised by iron accumulation in the basal ganglia, is a rare autosomal recessive neurodegenerative disorder caused by pantothenate kinase 2 (PANK2) gene mutations. The PANK2 gene is located on chromosome 20p13 and encodes pantothenate kinase. Herein, we identified one patient with PKAN who had mutations in the PANK2 gene.

Materials and methods: We performed clinical and radiographic investigations, and diagnosed this disease at the clinical and genetic levels.

Results: It is worth mentioning that the patient displayed an eye-of-the-tiger sign. Through scanning the exons and flanking intronic sequences of PANK2 in patient and control subjects, we report a compound heterozygote c. 260A?>?G (NM_001324191) and c.405dupC (NM_153638) for PANK2 mutations in a Chinese patient with clinical manifestation of progressive prosopospasm, dysarthria and gait disturbance. Bioinformatics analysis showed that two variants exhibited highly conserved residues across species.

Conclusion: we reported a patient presenting with atypical PKAN, and identified novel compound heterozygous PANK2 gene mutations..     

Pantothenate kinase-associated neurodegeneration in Korea: recurrent R440P mutation in PANK2 and outcome of deep brain stimulation

Background and Purpose: The purpose of this study was to evaluate the mutation status of PANK2 among Korean patients with pantothenate kinase‐associated neurodegeneration (PKAN) and to document the outcome of pallidal deep brain stimulation (DBS). Methods: Direct sequencing and deletion/duplication analysis of PANK2 were conducted in 12 patients (11 unrelated) with PKAN, diagnosed on the basis of extrapyramidal dysfunction and the ‘eye‐of‐the‐tiger sign’ on brain magnetic resonance imaging (MRI). Pallidal DBS was conducted in four patients, and the outcomes were measured using the Burke–Fahn–Marsden Dystonia Rating Scale (BFMDRS). Results: A PANK2 mutation was identified in both alleles in all patients. The most prevalent mutation was c.1319G>C (p.R440P) in 8/22 mutated alleles (36%). An intragenic deletion ranging from exons 2 to 4 was found in one allele (1/22, 4.5%) using deletion/duplication analysis. The outcome of pallidal DBS was favorable in two patients with atypical PKAN and moderate severity of dystonia. However, two patients with typical PKAN and relatively severe symptoms showed variable responses. Conclusions: The c.1319G>C (p.R440P) mutation appears to be a founder genotype among Korean patients with PKAN. Furthermore, this study provides additional data for the recent international effort to evaluate the efficacy of pallidal DBS in the treatment of patients with PKAN.     

Syndromes of neurodegeneration with brain iron accumulation (NBIA): an update on clinical presentations, histological and genetic underpinnings, and treatment considerations

In recent years, understanding of the syndromes of neurodegeneration with brain iron accumulation (NBIA) has grown considerably. In addition to the core syndromes of pantothenate kinsase-associated neurodegeneration (PKAN, NBIA1) and PLA2G6-associated neurodegeneration (PLAN, NBIA2), several other genetic causes have been identified. The acknowledged clinical spectrum has broadened, age-dependent presentations have been recognized, and we are becoming aware of overlap between the different NBIA disorders as well as with other diseases. Autopsy examination of genetically confirmed cases has demonstrated Lewy bodies and/or tangles in some subforms, bridging the gap to more common neurodegenerative disorders such as Parkinson's disease. NBIA genes map into related pathways, the understanding of which is important as we move toward mechanistic therapies. Our aim in this review is to provide an overview of not only the historical developments, clinical features, investigational findings, and therapeutic results but also the genetic and molecular underpinnings of the NBIA syndromes.     

Syndromes of neurodegeneration with brain iron accumulation

In parallel to recent developments of genetic techniques, understanding of the syndromes of neurodegeneration with brain iron accumulation has grown considerably. The acknowledged clinical spectrum continues to broaden, with age-dependent presentations being recognized. Postmortem brain examination of genetically confirmed cases has demonstrated Lewy bodies and/or tangles in some forms, bridging the gap to more common neurodegenerative disorders, including Parkinson disease. In this review, the major forms of neurodegeneration with brain iron accumulation (NBIA) are summarized, concentrating on clinical findings and molecular insights. In addition to pantothenate kinase-associated neurodegeneration (PKAN) and phospholipase A2-associated neurodegeneration (PLAN), fatty acid hydroxylase-associated neurodegeneration (FAHN) NBIA, mitochondrial protein-associated neurodegeneration, Kufor-Rakeb disease, aceruloplasminemia, neuroferritinopathy, and SENDA syndrome (static encephalopathy of childhood with neurodegeneration in adulthood) are discussed.     

Precision medicine in pantothenate kinase-associated neurodegeneration

Neurodegeneration with brain iron accumulation is a broad term that describes a heterogeneous group of progressive and invalidating neurologic disorders in which iron deposits in certain brain areas,mainly the basal ganglia.The predominant clinical symptoms include spasticity,progressive dystonia,Parkinson's disease-like symptoms,neuropsychiatric alterations,and retinal degeneration.Among the neurodegeneration with brain iron accumulation disorders,the most frequent subtype is pantothenate kinase-associated neurodegeneration(PKAN) caused by defects in the gene encoding the enzyme pantothenate kinase 2(PANK2)which catalyzed the first reaction of the coenzyme A biosynthesis pathway.Currently there is no effective treatment to prevent the inexorable course of these disorders.The aim of this review is to open up a discussion on the utility of using cellular models derived from patients as a valuable tool for the development of precision medicine in PKAN.Recently,we have described that dermal fibroblasts obtained from PKAN patients can manifest the main pathological changes of the disease such as intracellular iron accumulation accompanied by large amounts of lipofuscin granules,mitochondrial dysfunction and a pronounced increase of markers of oxidative stress.In addition,PKAN fibroblasts showed a morphological senescence-like phenotype.Interestingly,pantothenate supplementation,the substrate of the PANK2 enzyme,corrected all pathophysiological alterations in responder PKAN fibroblasts with low/residual PANK2 enzyme expression.However,pantothenate treatment had no favourable effect on PKAN fibroblasts harbouring mutations associated with the expression of a truncated/incomplete protein.The correction of pathological alterations by pantothenate in individual mutations was also verified in induced neurons obtained by direct reprograming of PKAN fibroblasts.Our observations indicate that pantothenate supplementation can increase/stabilize the expression levels of PANK2 in specific mutations.Fibroblasts and induced neurons derived from patients can provide a useful tool for recognizing PKAN patients who can respond to pantothenate treatment.The presence of low but significant PANK2 expression which can be increased in particular mutations gives valuable information which can support the treatment with high dose of pantothenate.The evaluation of personalized treatments in vitro of fibroblasts and neuronal cells derived from PKAN patients with a wide range of pharmacological options currently available,and monitoring its effect on the pathophysiological changes,can help for a better therapeutic strategy.In addition,these cell models will be also useful for testing the efficacy of new therapeutic options developed in the future.     

Childhood disorders of neurodegeneration with brain iron accumulation (NBIA)

Neurodegeneration with brain iron accumulation (NBIA) comprises a heterogeneous group of progressive complex motor disorders characterized by the presence of high brain iron, particularly within the basal ganglia. A number of autosomal recessive NBIA syndromes can present in childhood, most commonly pantothenate kinase-associated neurodegeneration (PKAN; due to mutations in the PANK2 gene) and phospholipase A2 group 6-associated neurodegeneration (PLAN; associated with genetic defects in PLA2G6). Mutations in the genes that cause these two neuroaxonal dystrophies are thought to disrupt the normal cellular functions of phospholipid remodelling and fatty acid metabolism. A significant proportion of children with an NBIA phenotype have no genetic diagnosis and there are, no doubt, additional as yet undiscovered genes that account for a number of these cases. NBIA disorders can be diagnostically challenging as there is often phenotypic overlap between the different disease entities. This review aims to define the clinical, radiological, and genetic features of such disorders, providing the clinician with a stepwise approach to appropriate neurological and genetic investigation, as well as a clinical management strategy for these neurodegenerative syndromes.     

Update on neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) defines a heterogeneous group of progressive neurodegenerative disorders characterized by excessive iron accumulation in the brain, particularly affecting the basal ganglia. In the recent years considerable development in the field of neurodegenerative disorders has been observed. Novel genetic methods such as autozygosity mapping have recently identified several genetic causes of NBIA. Our knowledge about clinical spectrum has broadened and we are now more aware of an overlap between the different NBIA disorders as well as with other diseases. Neuropathologic point of view has also been changed. It has been postulated that pantothenate kinase-associated neurodegeneration (PKAN) is not synucleinopathy. However, exact pathologic mechanism of NBIA remains unknown. The situation implicates a development of new therapies, which still are symptomatic and often unsatisfactory. In the present review, some of the main clinical presentations, investigational findings and therapeutic results of the different NBIA disorders will be presented.     

Partial deficit of pantothenate kinase 2 catalytic activity in a case of tremor-predominant neurodegeneration with brain iron accumulation.

We describe an atypical case of pantothenate kinase-associated neurodegeneration (PKAN) in which slowly progressive arm tremor was the predominant symptom beginning at the age of 25, with late-onset dystonia and dysarthria developing at the age of 50. Compound heterozygous mutations resulting in missense amino acid substitutions G521R and I529V were identified in the pantothenate kinase (PANK2) gene. We demonstrate that while the G521R mutation results in an unstable and inactive protein, the previously unreported I529V substitution has no apparent effect on the stability or catalytic activity of PanK2. The phenotype that results from this combination of mutations suggests that atypical presentations of PKAN may arise from partial deficits in PanK2 catalytic activity.     

A Novel PANK2 Mutation in a Patient with Atypical Pantothenate-Kinase-Associated Neurodegeneration Presenting with Adult-Onset Parkinsonism

Background

Pantothenate-kinase-associated neurodegeneration (PKAN) is an autosomal recessive neurodegenerative disorder that is characterized by progressive extrapyramidal signs, visual loss, and cognitive impairment. PKAN is caused by mutations in the pantothenate kinase gene (PANK2), which is located on chromosome 20p13 and encodes pantothenate kinase, the key regulatory enzyme in coenzyme-A biosynthesis.

Case Report

In this report we describe a case of atypical PKAN with a novel PANK2 mutation, presenting with a 10-year history of postural tremor involving both hands. Upon neurological examination, the patient''s face was masked and he spoke in a monotonous voice. The patient presented with mild bradykinesia and rigidity that involved all of the extremities. Horizontal saccadic eye movements were slow and fragmented. Brain MRI revealed a typical "eye-of-the-tiger" sign. A mutation analysis revealed three PANK2 mutations: two in exon 3 (Asp 378Gly and Leu385CysfsX13) and one in exon 4 (Arg440Pro).

Conclusions

Parkinsonism is not an unusual presenting symptom in patients with atypical PKAN, and so it is important for physicians to consider PKAN in the differential diagnosis of patients presenting with young-onset parkinsonism.     

Early-onset neurodegeneration with brain iron accumulation due to PANK2 mutation

Background: Pantothenate kinase-associated neurodegeneration (PKAN) is a neurodegenerative disorder caused by pantothenate kinase (PANK2) gene mutations. Brain magnetic resonance imaging (MRI) typically shows the “eye-of-the-tiger” sign, i.e. bilateral pallidal T2 hypointensity with a small central region of T2-hyperintensity. Aims: To describe clinical and MRI findings of a boy with early-onset neurodegeneration with brain iron accumulation due to PANK2 mutation. Methods: Clinical, neuroradiological and molecular investigations have been performed. Results: At first observation (2 years and 10 months) the boy presented only with developmental delay and toe-walking and isolated T2 hyperintensity within globi pallidi on brain MRI. One year later, small rounded areas of markedly low signal within the globi pallidi on T2∗- weighted images appeared in association with mild dystonia. PANK2 gene homozygous mutation confirmed the diagnosis of PKAN. Conclusions: In young children, PKAN should be suspected also before clinical and neuroradiological picture is fully indicative, to avoid delayed diagnosis of a genetic disease for which therapeutical options could be potentially useful if administered in paucisymptomatic subjects.     

Novel compound heterozygous mutations in the PANK2 gene in a Chinese patient with atypical pantothenate kinase-associated neurodegeneration.

We investigated the presence of mutations in the pantothenate kinase (PANK2) gene in a 27-year-old male Chinese patient with atypical pantothenate kinase-associated neurodegeneration (PKAN), formerly Hallervorden-Spatz syndrome. Automated DNA sequence analyses revealed compound heterozygous mutations in the exon 3 and 5. This patient had a 10-year history of PKAN characterized by a slight tremor of the right hand when writing at onset and a slow progressive rigidity of the neck and the right arm and resting tremor in upper extremities. Dysarthria, dysphagia, and dystonic-athetoid movements of the face and right fingers were marked. Magnetic resonance showed the typical "eye-of-the-tiger" sign.     

HARP syndrome is allelic with pantothenate kinase-associated neurodegeneration

HARP (hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa, and pallidal degeneration) is a rare syndrome with many clinical similarities to pantothenate kinase-associated neurodegeneration (PKAN, formerly Hallervorden-Spatz syndrome). Despite these common features, lipoprotein abnormalities have not been reported in PKAN. After the recent discovery of the genetic defect in PKAN, we report a homozygous nonsense mutation in exon 5 of the PANK2 gene that creates a stop codon at amino acid 371 (R371X) in the original HARP patient. This finding establishes that HARP is part of the PKAN disease spectrum.     

Genetic heterogeneity in patients with pantothenate kinase-associated neurodegeneration and classic magnetic resonance imaging eye-of-the-tiger pattern.

We performed a detailed molecular study in two unrelated families with pantothenate kinase-associated neurodegeneration (PKAN) and the specific magnetic resonance imaging (MRI) eye-of-the-tiger pattern. In the first family with classic PKAN, linkage analysis using polymorphic markers from the PANK2 region ruled out linkage with this locus, and no mutation of the PANK2 gene was found. In the second family with atypical PKAN, we identified a novel homozygous C-to-T transition at nucleotide 1069 of the PANK2 gene, which resulted in an arginine to tryptophane substitution at codon 357. As far as we are aware, this is the first case of classic PKAN with the specific MRI eye-of-the-tiger pattern not carrying a PANK2 mutation. Therefore, the present observation reinforces the notion of the phenotypic and genetic heterogeneity in PKAN.     

MRI,MR spectroscopy,and diffusion tensor imaging findings in patient with static encephalopathy of childhood with neurodegeneration in adulthood (SENDA)

Static encephalopathy of childhood with neurodegeneration in adulthood (SENDA) is a recently established disorder that is a subtype of neurodegeneration with brain iron accumulation (NBIA). We presented the first case report of SENDA of a 39-year-old female. She had psychomotor retardation from childhood and remained static for two decades. Then, at the age of 30, she developed severe dystonia and parkinsonism. Brain MRI revealed T2-weighted hypointensity signal in the globus pallidus and substantia nigra, and T1-weighted hyperintensity signal in the substantia nigra with a central hypointensity area. These clinical and imaging findings are characteristic of SENDA. Advanced MRI, including ¹H-MR spectroscopy (MRS) and diffusion tensor imaging (DTI), demonstrated similar findings of pantothenate kinase-associated neurodegeneration (PKAN), which is a major syndrome of SENDA. MRI plays a crucial role in the diagnosis of NBIA, especially SENDA.