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.

Olfactory status in neurodegeneration with brain iron accumulation disorders.

BACKGROUND: Olfactory dysfunction has been suggested as a diagnostic and discriminative biomarker in some neurodegenerative disorders. However, there are few studies regarding the olfactory status in rare diseases including neurodegeneration with brain iron accumulation (NBIA) disorders. METHODS: Genetically-confirmed NBIA patients were enrolled. Neurological and cognitive examinations were conducted according to the Pantothenate Kinase-Associated Neurodegeneration-Disease Rating Scale (PKAN-DRS) and the Mini-Mental State Examination (MMSE) questionnaire, respectively. Olfaction was assessed in three domains of odor threshold (OT), odor discrimination (OD), odor identification (OI), and total sum (TDI) score by the Sniffin' Sticks test. The olfactory scores were compared to a control group and a normative data set. RESULTS: Thirty-seven patients, including 22 PKAN, 6 Kufor Rakeb syndrome, 4 Mitochondrial membrane Protein-Associated Neurodegeneration (MPAN), 5 cases of other 4 subtypes, and 37 controls were enrolled. The mean PKAN-DRS score was 51.83±24.93. Sixteen patients (55.2%) had normal cognition based on MMSE. NBIA patients had significantly lower olfactory scores compared to the controls in TDI and all three subtests, and 60% of them were hyposmic according to the normative data. Including only the cognitively-normal patients, still, OI and TDI scores were significantly lower compared to the controls. The phospholipase A2-Associated Neurodegeneration (PLAN) and MPAN patients had a significantly lower OI score compared to the cognitively-matched PKAN patients. CONCLUSION: Olfactory impairment as a common finding in various subtypes of NBIA disorder can potentially be considered a discriminative biomarker. Better OI in PKAN compared to PLAN and MPAN patients may be related to the different underlying pathologies.

The first Vietnamese patient who presented late onset of pantothenate kinase-associated neurodegeneration diagnosed by whole exome sequencing: A case report.

RATIONALE: Pantothenate kinase-associated neurodegeneration (PKAN), also called Hallervorden-Spatz syndrome, is a rare autosomal recessive disease associated with brain iron accumulation and characterized by progressive dystonia, dementia, and dysarthria symptoms. PKAN, caused by a defective pantothenate kinase 2 (PANK2) gene, is the most common neurodegeneration with a brain iron accumulation (NBIA) group. The "eye of the tiger" sign in the magnetic resonance imaging demonstrated a bilateral hyperintense signal in the basal ganglia region on T2-weighted images, which is a characteristic feature of the diagnosis. PKAN is classified into 2 main types. The early-onset type (classic type) with rapid progression is characterized by symptoms of gait impairment and dystonia leading to loss of ambulation in early childhood. In the later-onset type (atypical type), slow progression usually takes place in the second decade of life with symptoms of neurodegeneration, dystonia, dysarthria, rigidity, choreoathetosis, and motor impairment. Until now, PKAN patients have only been reported in a few countries in Asia such as China, Korea, India, Iran, Taiwan, and Thailand. PATIENT CONCERNS: Here we report the first case of PKAN in Vietnam. The patient had a late onset but the disease progresses rapidly with symptoms of dyskinesia, dysphagia, and difficulty speaking. DIAGNOSES: Pantothenate kinase-associated neurodegeneration. INTERVENTIONS: Whole exome sequencing was performed to identify heterozygous mutations in the PANK2 gene (NM_153638.4) (c.856C>T, p.Arg286Cys and c.1351C>T, p.Arg451Ter) that has been confirmed as the cause of the disease. OUTCOMES: In this study, the first Vietnamese patient with late-onset PKAN was diagnosed by the whole exome sequencing method. LESSONS: The patient's case marks an important milestone for the first case in Vietnam. The results of the study will provide a scientific basis for clinicians in the diagnosis and genetic counseling of patients.

Concurrent PANK2 and OCA2 variants in a patient with retinal dystrophy, hypopigmented irides and neurodegeneration.

PURPOSE: To report a case of concurrent pantothenate kinase-associated neurodegeneration (PKAN) and oculocutaneous albinism (OCA) with dual PANK2 and OCA2 variants in a Chinese patient who presented with early-onset reduced vision, nyctalopia, and neurological symptoms. MATERIALS AND METHODS: Based on the ocular phenotype and provisional diagnosis of rod-cone dystrophy, genetic testing was pursued. Peripheral blood DNA extraction was carried out with the next-generation sequencing technique, which involved a population-specific medical exome virtual panel. Pre- and post-test counseling were carried out by clinical geneticists. RESULT: Homozygous missense variants in PANK2 {NM_153638.3}:c.655 G>A (p.(Gly219Ser)) and OCA2{NM_025160.6}:c.1327 G>A(p.(Val443Ile)) were identified. The molecular diagnoses of pantothenate kinase associated neurodegeneration (OMIM#234200) and albinism, oculocutaneous, type II (OMIM#203200) were supported by clinical findings. CONCLUSION: Two rare autosomal recessive diseases, pantothenate kinase-associated neurodegeneration (PKAN) and oculocutaneous albinism (OCA) were detected in our patient. Ocular and systemic manifestations, as well as neuroimaging findings were compatible with the diseases identified. Genetic analysis is imperative in making an accurate molecular diagnosis in these rare conditions to allow timely counseling, disease prognostication and management.

Novel Compound Heterozygous Mutation in PANK2 in a Patient with an Atypical Form of Pantothenate Kinase Associated Neurodegeneration and His Family.

Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal-recessive disease characterized by iron accumulation in the brain due to PANK2 gene mutation. The typical "eye-of-the-tiger" sign is the characteristic manifestation of brain magnetic resonance imaging (MRI). We report a Chinese patient with atypical PKAN whose brain MRI scans displayed the typical "eye-of-the-tiger" sign in bilateral pallidum. Genetic analysis identified a compound heterozygous mutation (c. 629-2A > T, c. 1130T > C) for the PANK2 gene. These two mutations were further demonstrated in his parents and other relatives.

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.

Psychiatric symptoms in an adolescent reveal a novel compound heterozygous mutation of the PANK2 gene in the atypical PKAN syndrome.

The proband in this study was a 16-year-old Mexican girl with psychotic and dyskinetic symptoms, and brain MRI showed at the basal ganglia the 'eye-of-the-tiger' sign. DNA direct sequencing identified a novel compound heterozygous mutation in the PANK2 gene. The diagnosis of pantothenate kinase-associated neurodegeneration (PKAN) disorder was made. This novel change increases the pool of PANK2 mutations. It supports the published data suggesting that PANK2 plays a significant role in patients expressing psychiatric phenotypes in the PKAN syndrome. When a patient presents with dyskinesia and psychiatric symptoms, PANK2 should be investigated as a possible diagnosis, and genetic consultation should be recommended.

PKAN neurodegeneration and residual PANK2 activities in patient erythrocytes.

OBJECTIVE: Pantothenate kinase 2-associated neurodegeneration (PKAN) is a rare neurodegenerative disease caused by mutations in the pantothenate kinase 2 (PANK2) gene. PKAN is associated with iron deposition in the basal ganglia and, occasionally, with the occurrence of misshaped erythrocytes (acanthocytes). The aim of this study was to assess residual activity of PANK2 in erythrocytes of PKAN patients and to correlate these data with the type of PANK2 mutations and the progression of neurodegeneration. METHODS: Residual PANK2 activities in erythrocytes of 14 PKAN patients and 14 related carriers were assessed by a radiometric assay. Clinical data on neurodegeneration included the Barry-Albright Dystonia Scale (BAD-Scale) besides further general patient features. A molecular visualization and analysis program was used to rationalize the influence of the PKAN causing mutations on a molecular level. RESULTS: Erythrocytes of PKAN patients had markedly reduced or no PANK2 activity. However, patients with at least one allele of the c.1583C > T (T528M) or the c.833G > T (R278L) variant exhibited 12-56% of residual PANK2 activity. In line, molecular modeling indicated only minor effects on enzyme structure for these point mutations. On average, these patients with c.1583C > T or c.833G > T variant had lower BAD scores corresponding to lower symptom severity than patients with other PANK2 point mutations. INTERPRETATION: Residual erythrocyte PANK2 activity could be a predictor for the progression of neurodegeneration in PKAN patients. Erythrocytes are an interesting patient-derived cell system with still underestimated diagnostic potential.

Natural history and genotype-phenotype correlation of pantothenate kinase-associated neurodegeneration.

AIMS: To investigate the natural history and genotype-phenotype correlation of pantothenate kinase-associated neurodegeneration. METHODS: We collected data of patients with PKAN by searching from available publications in English and Chinese. Patients diagnosed in our center (Peking University First Hospital) were also included. The difference in natural history and genotype between early-onset (<10 year of age at onset) and late-onset patients (≥10 year of age at onset) with PKAN was compared. RESULTS: A total of 248 patients were included. The median age at onset was 3.0 years in the early-onset group and 18.0 years in the late-onset group. Dystonia in lower limbs was the most common initial symptom in both groups. In the early-onset group, the median interval between the disease onset and occurrence of oromandibular dystonia, generalized dystonia, loss of independent ambulance was 6.0 years, 5.0 years, and 5.0 years. The corresponding values in late-onset group were 1.0 year, 4.0 years, and 6.0 years. About 20.0% died at median age of 12.5 years and 9.5 years after the onset in early-onset group. About 2.0% of the late-onset patients died during the follow-up. A total of 176 mutations were identified. Patients carrying two null alleles in PANK2 showed significantly earlier age of disease onset and progressed more rapidly to loss of independent ambulance. CONCLUSIONS: This study provided a comprehensive review on the natural history and genotype of 248 patients with PKAN. The results will serve as a historical control data for future clinical trial on PKAN.

Tongue Protrusion Dystonia in Pantothenate Kinase-Associated Neurodegeneration.

BACKGROUND: Tongue protrusion dystonia is an uncommon focal dystonia involving the lingual muscles. Causes of tongue protrusion dystonia include tardive dystonia, posthypoxic dystonia, neuroacanthocytosis, pantothenate kinase-associated neurodegeneration, and Lesch-Nyhan syndrome. METHOD: We summarize three children with pantothenate kinase-associated neurodegeneration and tongue protrusion dystonia. All three patients underwent careful neurological examination, brain magnetic resonance imaging, and genetic testing. RESULTS: Tongue protrusion dystonia was a prominent and disabling symptom in all three patients. Brain magnetic resonance imaging revealed a typical eye of the tiger sign in all patients. Two patients had the same genetic mutation (c.1168 A>T mutation, p.I390F). CONCLUSIONS: Tongue protrusion dystonia may be a clue to the underlying etiology of dystonia, including hereditary forms of dystonia. Among them, pantothenate kinase-associated neurodegeneration is an important cause, especially in children.

Incidence of PKAN determined by bioinformatic and population-based analysis of ~140,000 humans.

Panthothenate kinase-associated neurodegeneration (PKAN, OMIM 234200), is an inborn is an autosomal recessive inborn error of metabolism caused by pathogenic variants in PANK2. PANK2 encodes the enzyme pantothenate kinase 2 (EC 2.7.1.33), an essential regulatory enzyme in CoA biosynthesis. Clinical presentation includes dystonia, rigidity, bradykinesia, dysarthria, pigmentary retinopathy and dementia with variable age of onset ranging from childhood to adulthood. In order to provide an accurate incidence estimate of PKAN, we conducted a systematic review of the literature and databases for pathogenic mutations and constructed a bioinformatic profile for pathogenic missense variants in PANK2. We then studied the gnomAD cohort of ~140,000 unrelated adults from global populations to determine the allele frequency of the variants in PANK2 reported pathogenic for PKAN and for those additional variants identified in gnomAD that met bioinformatics criteria for being potentially pathogenic. Incidence was estimated based on three different models using the allele frequencies of pathogenic PKAN variants with or without those bioinformatically determined to be potentially pathogenic. Disease incidence calculations showed PKAN incidence ranging from 1:396,006 in Europeans, 1:1,526,982 in Africans, 1:480,826 in Latino, 1:523,551 in East Asians and 1:531,118 in South Asians. These results indicate PKAN is expected to occur in approximately 2 of every 1 million live births globally outside of Africa, and has a much lower incidence 1 in 1.5 million live births in the African population.

Basal ganglia calcification and novel compound heterozygous mutations in the PANK2 gene in a Chinese boy with classic Pantothenate kinase-associated neurodegeneration: A case report.

RATIONALE: Pantothenate kinase-associated neurodegeneration (PKAN) represents an autosomal recessive hereditary disease. In this report, a PANK2 gene mutation in a Chinese child was identified, as well as detections of PKAN among his family members. Our findings exposed a world-wide novel compound heterozygous mutation. PATIENT CONCERNS: We described a 6-year-old male patient with PKAN, exhibiting involuntary movement for a period of 1.5 years, as well as feeding difficulties for 2 weeks. DIAGNOSIS: Due to brain computed tomography and magnetic resonance imaging results, and patient behavior, the attending physician suspected a hereditary effect. INTERVENTIONS: The patient sample underwent high-throughput sequencing. Subsequently, his parents and sister were screened for the mutations identified in the patient genome. OUTCOMES: High-throughput sequencing revealed a novel complex heterozygous mutation of the PANK2 gene, which was detected in the second and fourth exons, c.A650G, and c.T1341G, respectively, resulting in amino acid alterations (p.D217G and p.D447E, respectively). The child's father was confirmed to possess a heterozygous c.A650G mutation, while his mother was heterozygous for the c.T1341G mutation. LESSONS: The key finding of the study encompassed the detection of a novel PANK2 gene mutation in a child of Chinese ethnicity with PKAN. The PANK2 gene c.A650G, as well as c.T1341G, mutations may be potential mutation hotspots in children with PKAN in Mainland China.

On the complexity of clinical and molecular bases of neurodegeneration with brain iron accumulation.

Neurodegeneration with brain iron accumulation (NBIA) is a group of inherited heterogeneous neurodegenerative rare disorders. These patients present with dystonia, spasticity, parkinsonism and neuropsychiatric disturbances, along with brain magnetic resonance imaging (MRI) evidence of iron accumulation. In sum, they are devastating disorders and to date, there is no specific treatment. Ten NBIA genes are accepted: PANK2, PLA2G6, C19orf12, COASY, FA2H, ATP13A2, WDR45, FTL, CP, and DCAF17; and nonetheless, a relevant percentage of patients remain without genetic diagnosis, suggesting that other novel NBIA genes remain to be discovered. Overlapping complex clinical pictures render an accurate differential diagnosis difficult. Little is known about the pathophysiology of NBIAs. The reported NBIA genes take part in a variety of pathways: CoA synthesis, lipid and iron metabolism, autophagy, and membrane remodeling. The next-generation sequencing revolution has achieved relevant advances in genetics of Mendelian diseases and provide new genes for NBIAs, which are investigated according to 2 main strategies: genes involved in disorders with similar phenotype and genes that play a role in a pathway of interest. To achieve an effective therapy for NBIA patients, a better understanding of the biological process underlying disease is crucial, moving toward a new age of precision medicine.

[Phenotypic and genotypic features of twenty children with classic pantothenate kinase-associated neurodegeneration].

Objective: To explore the phenotypic and genotypic characteristics in Chinese children with classic pantothenate kinase-associated neurodegeneration (PKAN). Method: The clinical, radiographic and genetic data of all PKAN patients diagnosed at pediatric department of Peking University First Hospital from November 2006 to December 2016 were retrospectively collected and analyzed. Result: Twenty patients with classic PKAN were included in the study. The median age at onset was 3.5 years (ranging from 1.0 to 10.0 years), and the most common initial symptom was gait disturbance (16 cases). At the last evaluation, the clinical features were limbs dystonia (20 cases), dysarthria (16 cases), dysphagia (11 cases), pyramidal sign (7 cases), mental regression (3 cases) and pigmentary retinopathy (5 cases). For those classic PKAN patients, the median time from onset of disease to loss of independent ambulation was 6.9 years (ranging from 2.0 to 12.0 years). Imaging data showed, except "eye of tiger" in MRI (19 cases), globus pallidus calcification in CT was also found in four patients. In gene testing, 26 different mutations in PANK2 gene were identified, and 16 of 26 were novel mutations. Moreover, c. 1502T>C (p.Ile501Asn) was the most common mutation (4 cases). Conclusion: Dystonia is the major neurologic feature of classic PKAN. Disease progression is rapid, with loss of independent ambulation within 10 years after onset. Except "eye of tiger" in MRI, globus pallidus calcification in CT may be another imaging feature of PKAN.Sixteen novel mutations of PANK2 gene were identified in the study.

Clinical rating scale for pantothenate kinase-associated neurodegeneration: A pilot study.

BACKGROUND: Pantothenate kinase-associated neurodegeneration is a progressive neurological disorder occurring in both childhood and adulthood. The objective of this study was to design and pilot-test a disease-specific clinical rating scale for the assessment of patients with pantothenate kinase-associated neurodegeneration. METHODS: In this international cross-sectional study, patients were examined at the referral centers following a standardized protocol. The motor examination was filmed, allowing 3 independent specialists in movement disorders to analyze 28 patients for interrater reliability assessment. The scale included 34 items (maximal score, 135) encompassing 6 subscales for cognition, behavior, disability, parkinsonism, dystonia, and other neurological signs. RESULTS: Forty-seven genetically confirmed patients (30 ± 17 years; range, 6-77 years) were examined with the scale (mean score, 62 ± 21; range, 20-106). Dystonia with prominent cranial involvement and atypical parkinsonian features were present in all patients. Other common signs were cognitive impairment, psychiatric features, and slow and hypometric saccades. Dystonia, parkinsonism, and other neurological features had a moderate to strong correlation with disability. The scale showed good internal consistency for the total scale (Cronbach's α = 0.87). On interrater analysis, weighted kappa values (0.30-0.93) showed substantial or excellent agreement in 85% of the items. The scale also discriminated a subgroup of homozygous c.1583C>T patients with lower scores, supporting construct validity for the scale. CONCLUSIONS: The proposed scale seems to be a reliable and valid instrument for the assessment of pediatric and adult patients with pantothenate kinase-associated neurodegeneration. Additional validation studies with a larger sample size will be required to confirm the present results and to complete the scale validation testing. © 2017 International Parkinson and Movement Disorder Society.

Atypical pantothenate kinase-associated neurodegeneration: Clinical description of two brothers and a review of the literature.

Two clinical forms of pantothenate kinase-associated neurodegeneration (PKAN) have been described: typical PKAN and atypical PKAN. Atypical PKAN has later onset and a slower course of disease. This report describes two siblings with the atypical form of PKAN, combining dystonia, irritability and a dysmorphia syndrome. In addition, a review of the literature was carried out for all published cases of atypical PKAN to gather descriptions of its various clinical presentations, age of onset and MRI findings, and to highlight the different treatments used for PKAN patients.