Idiopathic basal ganglia calcifications: an atypical presentation of PKAN

Abnormal Brain Iron Accumulation is a Rare Finding in Down Syndrome Regression Disorder

BACKGROUND

Down syndrome regression disorder (DSRD) is characterized by the sudden loss of adaptive function, cognitive-executive function, and language with abnormal sleep and/or motor control.

METHODS

Clinical, laboratory, and imaging data from three individuals with DSRD and iron on brain imaging were reviewed.

RESULTS

Three patients with Down syndrome presented with new onset of flat affect, depression, reduced speech, and other neurological symptoms consistent with DSRD. Magnetic resonance imaging showed abnormal iron accumulation in the basal ganglia, as well as calcification in two cases. Molecular diagnostic testing for neurodegeneration with brain iron accumulation was negative in the two individuals tested.

CONCLUSIONS

These individuals presented suggest that a subset of individuals with DSRD have abnormal brain iron accumulation. Motor control symptoms reported in DSRD, such as stereotypies and parkinsonism, may reflect this basal ganglia involvement. The presence of abnormal brain iron should not delay or preclude diagnosis and treatment for DSRD.

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.

MRI of neurodegeneration with brain iron accumulation

PURPOSE OF REVIEW

The diagnosis of neurodegeneration with brain iron accumulation (NBIA) typically associates various extrapyramidal and pyramidal features, cognitive and psychiatric symptoms with bilateral hypointensities in the globus pallidus on iron-sensitive magnetic resonance images, reflecting the alteration of iron homeostasis in this area. This article details the contribution of MRI in the diagnosis by summarizing and comparing MRI patterns of the various NBIA subtypes.

RECENT FINDINGS

MRI almost always shows characteristic changes combining iron accumulation and additional neuroimaging abnormalities. Iron-sensitive MRI shows iron deposition in the basal ganglia, particularly in bilateral globus pallidus and substantia nigra. Other regions may be affected depending on the NBIA subtypes including the cerebellum and dentate nucleus, the midbrain, the striatum, the thalamus, and the cortex. Atrophy of the cerebellum, brainstem, corpus callosum and cortex, and white matter changes may be associated and worsen with disease duration. Iron deposition can be quantified using R2 or quantitative susceptibility mapping.

SUMMARY

Recent MRI advances allow depicting differences between the various subtypes of NBIA, providing a useful analytical framework for clinicians. Standardization of protocols for image acquisition and analysis may help improving the detection of imaging changes associated with NBIA and the quantification of iron deposition.

Brain MRI Pattern Recognition in Neurodegeneration With Brain Iron Accumulation

Most neurodegeneration with brain iron accumulation (NBIA) disorders can be distinguished by identifying characteristic changes on magnetic resonance imaging (MRI) in combination with clinical findings. However, a significant number of patients with an NBIA disorder confirmed by genetic testing have MRI features that are atypical for their specific disease. The appearance of specific MRI patterns depends on the stage of the disease and the patient's age at evaluation. MRI interpretation can be challenging because of heterogeneously acquired MRI datasets, individual interpreter bias, and lack of quantitative data. Therefore, optimal acquisition and interpretation of MRI data are needed to better define MRI phenotypes in NBIA disorders. The stepwise approach outlined here may help to identify NBIA disorders and delineate the natural course of MRI-identified changes.

[Basal ganglia calcification]

Calcifications of the basal ganglia are frequently seen on the cerebral CT scans and particularly in the globus pallidus. Their frequency increases physiologically with age after 50 years old. However, pathological processes can also be associated with calcium deposits in the gray nuclei, posterior fossa or white matter. Unilateral calcification is often related to an acquired origin whereas bilateral ones are mostly linked to an acquired or genetic origin that will be sought after eliminating a perturbation of phosphocalcic metabolism. In pathological contexts, these calcifications may be accompanied by neurological symptoms related to the underlying disease: Parkinson's syndrome, psychiatric and cognitive disorders, epilepsy or headache. The purpose of this article is to provide a diagnostic aid, in addition to clinical and biology, through the analysis of calcification topography and the study of different MRI sequences.

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.

Mechanisms of calcification in Fahr disease and exposure of potential therapeutic targets

Purpose of review

There is growing interest in disorders involved in ectopic mineralization. Fahr disease or idiopathic basal ganglia calcification can serve as a model for ectopic mineralization in the basal ganglia, which is fairly common in the general population. In this review, we will focus on causative gene mutations and corresponding pathophysiologic pathways in Fahr disease.

Recent findings

Patients with Fahr disease have a variability of symptoms, such as movement disorders, psychiatric signs, and cognitive impairment, but can also be asymptomatic. Fahr disease is mostly autosomal dominant inherited, and there are mutations found in 4 causative genes. Mutations in SLC20A2 and XPR1 lead to a disrupted phosphate metabolism involving brain-specific inorganic phosphate transporters. Mutations in PDGFB and PDGFRB are associated with disrupted blood-brain barrier integrity and dysfunctional pericyte maintenance. In addition, the MYORG gene has recently been discovered to be involved in the autosomal recessive inheritance of Fahr.

Summary

Knowledge about the mutations and corresponding pathways may expose therapeutic opportunities for patients with Fahr disease and vascular calcifications in the brain in general.

Basal ganglia calcifications (Fahr's syndrome): related conditions and clinical features

Basal ganglia calcifications could be incidental findings up to 20% of asymptomatic patients undergoing CT or MRI scan. The presence of neuropsychiatric symptoms associated with bilateral basal ganglia calcifications (which could occur in other peculiar brain structures, such as dentate nuclei) identifies a clinical picture defined as Fahr's Disease. This denomination mainly refers to idiopathic forms in which no metabolic or other underlying causes are identified. Recently, mutations in four different genes (SLC20A2, PDGFRB, PDGFB, and XPR1) were identified, together with novel mutations in the Myogenic Regulating Glycosylase gene, causing the occurrence of movement disorders, cognitive decline, and psychiatric symptoms. On the other hand, secondary forms, also identified as Fahr's syndrome, have been associated with different conditions: endocrine abnormalities of PTH, such as hypoparathyroidism, other genetically determined conditions, brain infections, or toxic exposure. The underlying pathophysiology seems to be related to an abnormal calcium/phosphorus homeostasis and transportation and alteration of the blood-brain barrier.

Novel PANK2 mutation in a Chinese boy with PANK2-associated neurodegeneration: A case report and review of Chinese cases

RATIONALE

Pantothenate kinase-associated neurodegeneration (PKAN), also called Hallervorden-Spatz Syndrome (HSS), is a rare neurodegeneration with brain iron accumulation from pantothenate kinase 2 gene (PANK2) mutation characterized as extrapyramidal symptoms. However, few studies involving PKAN patients were reported in China. This study was conducted to identify the genetic mutations in a Chinese boy with PKAN, and to review all PANK2 mutations reported in Chinese cases with PKAN.

PATIENT CONCERN

We reported a 23-year-old Chinese boy with PKAN, exhibiting difficulty in writing and manipulation using right hand with slow progression for 12 years. He spoke with a severe stutter when he was 15 years old.

DIAGNOSIS

Considering results of magnetic resonance images, brain computed tomography and medical history, the case was suspected to be related to genetic factors.

INTERVENTIONS

Whole exome sequencing was arranged, and the mutations were identified in his parents' genome.

OUTCOMES

In the present study, whole exome sequencing revealed 2 novel mutations (c.1696C > G in exon 7 and c.1160_c.1161insG in exon3) of the PANK2 gene in the proband. c.1696C > G and c.1160_c.1161insG, respectively, were confirmed in his father and mother. We also reviewed 14 different PANK2 mutations, most of which were missense type in Chinese cases. Those mutations did not show apparent hotspots, but exon 3 and 4 were frequently involved.

LESSONS

Two novel compound heterozygous mutations were identified and considered to be pathogenic in PKAN patients. This review of the reports indicated that atypical PKAN is the more common phenotype in China and no apparent genotype-phenotype correlation was found.

Assessment of Physiological Intracranial Calcification in Healthy Adults Using 18F-NaF PET/CT

The aim of this research study was to determine the role of 18F-Sodium fluoride (NaF) PET/CT imaging in the assessment of physiologic molecular calcification in the intra-cranial structures. We also examined the association of NaF accumulation with age as well as Hounsfield unit (HU) in certain anatomical sites that are known to calcify with normal aging. Methods: A total of 78 healthy subjects from the Cardiovascular Molecular Calcification Assessed by 18F-NaF PET/CT (CAMONA) clinical trial (38 females and 40 males) were included in this retrospective study. The mean age was 45.28 ±14.15 years (21-75). Mean standardized uptake values (SUVmean) was used to measure NaF accumulation in the choroid plexus and epithalamus (pineal gland and habenula). Maximum HU was also measured for each ROI. Correlation analysis was conducted to assess the association between parameters. Results: Mean SUVmean was 0.42 ± 0.26 in the right choroid plexus, 0.39 ±25 in the left choroid plexus, and 0.23±0.08 in the epithalamus. Significant positive correlations were present between NaF uptake and age in the right choroid plexus (r=0.61, P < 0.0001), left choroid plexus (r=0.63, p<0.0001), and epithalamus (r=0.36, P = 0.001). NaF uptake significantly correlated with HU in the right choroid plexus (r=0.52, P < 0.0001), left choroid plexus (r=0.57, p<0.0001), and epithalamus (r=0.25, P = 0.03). Conclusion: NaF could be used in the assessment of physiological calcification in several intracranial structures. We report significant associations between NaF uptake and aging as well as HU in the calcified choroid plexus and epithalamus. Our findings further support the growing interest to utilize NaF for detecting extra-osseous, molecular calcification, and this powerful probe has potential applications in the evaluation of various age-related, neurodegenerative brain processes.

Intracranial Calcifications in Young Children

Intracranial calcifications in young infants, while suggesting intrauterine infections, can also be due to numerous other conditions, including rare genetic disorders. We describe 2 children in whom the presence and pattern of intracranial calcifications led to the diagnosis of uncommon genetic disorders, Adams-Oliver syndrome and Aicardi-Goutieres syndrome. Differentiating genetic conditions from intrauterine infections or other causes of intracranial calcifications enables practitioners to provide accurate counseling regarding prognosis and recurrence risk.

Looking Deep into the Eye-of-the-Tiger in Pantothenate Kinase-Associated Neurodegeneration

BACKGROUND AND PURPOSE

A detailed delineation of the MR imaging changes in the globus pallidus in pantothenate kinase-associated neurodegeneration will be helpful for diagnosis and monitoring of patients. The aim of this study was to determine the morphologic spectrum of the "eye-of-the-tiger" sign and the topographic pattern of iron deposition in a group of patients with pantothenate kinase-associated neurodegeneration.

MATERIALS AND METHODS

Seventy-four MR imaging scans from 54 individuals with PANK2 mutations were analyzed for signal patterns in the globus pallidus. Sixteen SWI data from 15 patients who underwent 1.5T (n = 7), 3T (n = 7), and 7T (n = 2) MR imaging were included to visualize the iron topography.

RESULTS

The linear hyperintensity alongside the medial border of the globus pallidus was the earliest T2 signal change. This finding was evident before SWI changes from iron deposition became visible. T2WI performed in early childhood mostly showed isolated hyperintense signal. In adult patients, marked signal reduction within an earlier hyperintense center resulting from iron accumulation led to the loss of signal difference between the central and surrounding areas. Signal hypointensity on SWI progressed from the medial to the lateral portion of the globus pallidus with increasing age. The fiber connections between the medial globus pallidus and the anteromedial aspect of the substantia nigra and subthalamic nucleus were markedly hypointense on SWI.

CONCLUSIONS

In pantothenate kinase-associated neurodegeneration, the globus pallidus MR imaging changes using SWI develop as region-specific and age-dependent phenomena. Signal inhomogeneity was observed across the globus pallidus in pantothenate kinase-associated neurodegeneration and should be considered when determining the concentration of iron.

Brain Calcification and Movement Disorders

Brain calcifications may be an incidental finding on neuroimaging in normal, particularly older individuals, but can also indicate numerous hereditary and nonhereditary syndromes, and metabolic, environmental, infectious, autoimmune, mitochondrial, traumatic, or toxic disorders. Bilateral calcifications most commonly affecting the basal ganglia may often be found in idiopathic cases, and a new term, primary familial brain calcification (PFBC), has been proposed that recognizes the genetic causes of the disorder and that calcifications occurred well beyond the basal ganglia. PFBC, usually inherited in an autosomal dominant fashion, is both an intrafamilial and an interfamilial heterogeneous disorder, clinically characterized by an insidious and progressive development of movement disorders, cognitive decline, and psychiatric symptoms, but also cerebellar ataxia, pyramidal signs, and sometimes isolated seizures and headaches/migraines. Heterozygous mutations in four genes (SLC20A2, PDGFRB, PDGFB, XPR1) have recently proved to be the causes of the autosomal dominant forms of PFBC, also suggesting disrupted phosphate homeostasis as "an underlying and converging" pathophysiological mechanism. However, to date, it is not possible to anticipate with acceptable certainty any of known genetic causes of PFBC on the basis of the type, severity, pattern of distribution, or combination of movement disorders (mainly parkinsonism, with or without tremor, but also dystonia, chorea, paroxysmal kinesigenic dyskinesia, orofacial dyskinesia, and gait and speech disorders).

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.

The NIH Undiagnosed Diseases Program and Network: Applications to modern medicine

INTRODUCTION

The inability of some seriously and chronically ill individuals to receive a definitive diagnosis represents an unmet medical need. In 2008, the NIH Undiagnosed Diseases Program (UDP) was established to provide answers to patients with mysterious conditions that long eluded diagnosis and to advance medical knowledge. Patients admitted to the NIH UDP undergo a five-day hospitalization, facilitating highly collaborative clinical evaluations and a detailed, standardized documentation of the individual's phenotype. Bedside and bench investigations are tightly coupled. Genetic studies include commercially available testing, single nucleotide polymorphism microarray analysis, and family exomic sequencing studies. Selected gene variants are evaluated by collaborators using informatics, in vitro cell studies, and functional assays in model systems (fly, zebrafish, worm, or mouse).

INSIGHTS FROM THE UDP

In seven years, the UDP received 2954 complete applications and evaluated 863 individuals. Nine vignettes (two unpublished) illustrate the relevance of an undiagnosed diseases program to complex and common disorders, the coincidence of multiple rare single gene disorders in individual patients, newly recognized mechanisms of disease, and the application of precision medicine to patient care.

CONCLUSIONS

The UDP provides examples of the benefits expected to accrue with the recent launch of a national Undiagnosed Diseases Network (UDN). The UDN should accelerate rare disease diagnosis and new disease discovery, enhance the likelihood of diagnosing known diseases in patients with uncommon phenotypes, improve management strategies, and advance medical research.

Genetics and molecular biology of brain calcification

Brain calcification is a common neuroimaging finding in patients with neurological, metabolic, or developmental disorders, mitochondrial diseases, infectious diseases, traumatic or toxic history, as well as in otherwise normal older people. Patients with brain calcification may exhibit movement disorders, seizures, cognitive impairment, and a variety of other neurologic and psychiatric symptoms. Brain calcification may also present as a single, isolated neuroimaging finding. When no specific cause is evident, a genetic etiology should be considered. The aim of the review is to highlight clinical disorders associated with brain calcification and provide summary of current knowledge of diagnosis, genetics, and pathogenesis of brain calcification.

Basal ganglia calcification in a patient with beta-propeller protein-associated neurodegeneration

BACKGROUND

Beta-propeller protein-associated neurodegeneration is a newly described X-linked dominant condition due to heterozygous mutations in WDR45. The condition is associated with characteristic changes on brain magnetic resonance imaging. Previous literature relating to this disorder has not specifically referred to intracranial calcification.

METHODS

A female patient presented with significant developmental delay in early childhood and subsequently demonstrated neurodegeneration with progressive dystonia and dementia in her third decade. Brain magnetic resonance imaging revealed low signal in the substantia nigra and both globus pallidi on T2-weighted imaging, with no eye-of-the-tiger sign. Computed tomography revealed bilateral dense calcification of the globus pallidus. We performed Sanger sequencing of the WDR45 gene in the patient and her parents.

RESULTS

We identified a heterozygous c.488del C p.Pro163Argfs*34 variant in exon 8 of WDR45. Neither parent carried the same mutation, indicating that the molecular change had occurred de novo.

CONCLUSIONS

Although the characteristic features of beta-propeller protein-associated neurodegeneration were present in our patient, the observation of basal ganglia calcification was considered atypical. Previous descriptions of basal ganglia calcification in individuals with neuronal brain iron accumulation led us to review the frequency of calcification in these disorders.