Chorea-acanthocytosis: a report of three new families and implications for genetic counselling

Identification of four novel mutations in VSP13A in Iranian patients with Chorea-acanthocytosis (ChAc)

Chorea-acanthocytosis (ChAc) is a rare autosomal recessive neurodegenerative disorder characterized by a variety of involuntary movements, predominantly chorea, and the presence of acanthocytosis in peripheral blood smears. ChAc is caused by mutations in the vacuolar protein sorting-associated protein 13A (VPS13A) gene. The aim of the present study was to conduct a clinical and genetic analysis of five patients with suspected ChAc in Iran. This study included five patients who were referred to the genetic department of the Endocrinology and Metabolism Research Institute between 2020 and 2022, with a suspicion of ChAc. Clinical features and the presence of characteristic MRI findings were evaluated in the patients. Whole-exome sequencing (WES) followed by Sanger sequencing was employed to identify the disease-causing variants. The functional effects of novel mutations were analyzed by specific bioinformatics prediction tools. WES and data analysis revealed the presence of five distinct VPS13A mutations in the patients, four of which were novel. These included one nonsense mutation (p.L984X), and three splice site mutations (c.755-1G>A, c.144+1 G>C, c.2512+1G>A). All mutations were validated by Sanger sequencing, and in silico analysis predicted that all mutations were pathogenic. This study provides the first molecular genetic characteristics of Iranian patients with ChAc, identifying four novel mutations in the VPS13A gene. These findings expand the VPS13A variants spectrum and confirm the clinical variability in ChAc patients.

A parasitic fungus employs mutated eIF4A to survive on rocaglate-synthesizing Aglaia plants

Plants often generate secondary metabolites as defense mechanisms against parasites. Although some fungi may potentially overcome the barrier presented by antimicrobial compounds, only a limited number of examples and molecular mechanisms of resistance have been reported. Here, we found an Aglaia plant-parasitizing fungus that overcomes the toxicity of rocaglates, which are translation inhibitors synthesized by the plant, through an amino acid substitution in a eukaryotic translation initiation factor (eIF). De novo transcriptome assembly revealed that the fungus belongs to the Ophiocordyceps genus and that its eIF4A, a molecular target of rocaglates, harbors an amino acid substitution critical for rocaglate binding. Ribosome profiling harnessing a cucumber-infecting fungus, Colletotrichum orbiculare, demonstrated that the translational inhibitory effects of rocaglates were largely attenuated by the mutation found in the Aglaia parasite. The engineered C. orbiculare showed a survival advantage on cucumber plants with rocaglates. Our study exemplifies a plant-fungus tug-of-war centered on secondary metabolites produced by host plants.

Juvenile Huntington's Disease

A significant minority of cases of Huntington's disease commence before the age of 20 years and these juvenile cases are more likely to demonstrate paternal transmission and a clinical picture dominated by rigidity. Genetic research and positron emission tomography may make early diagnosis easier but predictive testing in childhood is replete with serious problems. There is no specific treatment for this fatal disorder. Juvenile Huntington's disease has a similar pathology and biochemistry to the adult condition despite a shorter course and certain clinical differences, such as rigidity and convulsions. Racial differences are explored.

Developments in neuroacanthocytosis: Expanding the spectrum of choreatic syndromes

As with other neurodegenerative disorders, research into the group of diseases known under the umbrella term of "neuroacanthocytosis" has greatly benefited from the identification of causative genes. The distinct and unifying aspect of these disorders is the presence of thorny deformations of circulating erythrocytes. This may be due to abnormal properties of red cell membranes, which could lead to insights into mechanisms of neurodegeneration. Research approaches in this field, in addition to examining functions and protein interactions of the affected proteins with particular respect to neurons, have also drawn upon the expertise of hematologists and red cell membrane biologists. In this article, recent developments in the field are presented.

Familial temporal lobe epilepsy as a presenting feature of choreoacanthocytosis

PURPOSE

Choreoacanthocytosis (ChAc) is an autosomal recessive disorder caused by mutations in VPS13A on chromosome 9q21 and characterized by neurodegeneration and red cell acanthocytosis. Seizures are not uncommon in ChAc but have not been well characterized in the literature. We report two ChAc families in which patients presented with temporal lobe epilepsy.

METHODS

Detailed medical and family histories were obtained. EEG, video-telemetry, brain magnetic resonance imaging (MRI) with volumetric studies of amygdala and hippocampus, as well as neuropsychological testing were performed. Blood smears were examined for acanthocytosis. Mutation analysis of VPS13A was carried out in five patients.

RESULTS

Six patients in three sibships were initially seen with seizures. Age at seizure onset ranged from 22 to 38 years. Seizures preceded other clinical manifestations of ChAc by < or = 15 years. The epileptic aura consisted of a sensation of déjà-vu, fear, hallucinations, palpitations, or vertigo. EEG with video-telemetry showed epileptiform discharges originating either from one or both temporal lobes. Epilepsy was generally well controlled, but some patients had periods of increased seizure frequency requiring treatment with multiple antiepileptic drugs (AEDs). Both families shared a deletion of exons 70-73 of VPS13A, extending to exons 6-7 of GNA14.

CONCLUSIONS

Temporal lobe epilepsy may be the presenting feature of ChAc and may delay its diagnosis. Epilepsy in ChAc patients represents a challenge, because seizures may at times be difficult to control, and some AEDs may worsen the involuntary movements. Mutations in VPS13A or GNA14 or both may be associated with clinical features of temporal lobe epilepsy.

Testing for acanthocytosis A prospective reader-blinded study in movement disorder patients

The presence of acanthocytosis in peripheral blood smears remains the hallmark of the clinical diagnosis of most neuroacanthocytosis syndromes, such as chorea-acanthocytosis (ChAc) and McLeod syndrome. Genetic analyses and/or specific laboratory tests are available only for a minority of these disorders. Testing for acanthocytosis is hampered by the lack of data on normal amounts of acanthocytes assessed by a standardized method. We report a prospective reader-blinded study designed to establish control values for abnormally shaped erythrocytes in healthy volunteers and patients with movement disorders (MDs) using light microscopic assessment of erythrocyte morphology in standard EDTA and isotonically diluted blood samples. We investigated a total of 100 patients fulfilling clinical criteria of specific MDs, 31 patients with MDs not matching any clinical criteria, and 37 healthy controls. In patients with diagnosed MDs and healthy controls, acanthocytes in dry blood smears were significantly more frequent following isotonic dilution compared with standard EDTA blood. In unfixed wet blood preparations of both EDTA blood and isotonically diluted blood, acanthocyte levels were significantly higher than in standard dry blood smear preparations. There were no statistical differences of acanthocyte levels in all test conditions between diagnosed MDs and healthy volunteers. There was no significant correlation of acanthocyte levels in all blood samples and preparations with age, sex or diagnosis. Thus, normal values were defined as the 99th percentile of combined results of the two groups of volunteers. Diluted blood combined with wet blood preparation showed high specificity (0.98) and the highest sensitivity of all test procedures (all genetically confirmed ChAc patients were detected). The reported method is cheap, readily available, and provides high specificity and sensitivity in respect to clinically relevant acanthocytosis. The use of isotonically diluted blood samples combined with unfixed wet blood preparation with a normal range of <6.3% of total erythrocytes is recommended to search for significant acanthocytosis in movement disorders.

Spectrum of movement disorders in neuroferritinopathy

Neuroferritinopathy is a recently recognized, dominantly inherited movement disorder caused by a mutation of the ferritin light chain gene. We present video case reports of 4 individuals with neuroferritinopathy chosen to illustrate how this disorder can present and subsequently progress clinically. The clinical phenotype of this disorder is highly variable with symptoms beginning in the third to sixth decades. Chorea, dystonia, or an akinetic-rigid syndrome can predominate in different individuals. Neuroferritinopathy is not restricted to the UK and it has been described in apparently sporadic cases. The diagnosis should therefore be considered in patients with a wide variety of different movement disorders. Characteristic neuroimaging assists in identifying affected individuals.

Genetic epidemiology of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a late onset, rapidly progressive and ultimately fatal neurological disorder, caused by the loss of motor neurons in the brain and spinal cord. Familial aggregation of ALS, with an age-dependent but high penetrance, is a major risk factor for ALS. Familial ALS (FALS) is clinically and genetically heterogeneous. Three genes and linkage to four additional gene loci have been identified so far and may either predominantly lead to ALS (ALSI-ALS6) or cause multisystem neurodegeneration with ALS as an occasional symptom (tauopathies, ALS-dementia complex). This review presents a tentative classification of the "major" ALS genes and ALS "susceptibility" genes, that may act as susceptibility factors for neurodegeneration in interaction with other genetic or environmental risk factors. Considering that mutations in ALS genes explain approximately 10% of familial as well as sporadic ALS, and most remaining cases of the discase are thought to result form the interaction of several genes and environmental factors, ALS is a paradigm for multifactorial discases.

Severe generalized dystonia due to primary putaminal degeneration: case report and review of the literature

Putaminal lesions of a variety of etiologies may cause secondary dystonia. We report on a case of primary putaminal degeneration as a cause of severe childhood-onset generalized dystonia and review the literature of the pathology of dystonia. A 44-year-old patient with severe generalized childhood-onset dystonia and macrocephaly underwent neurological evaluation and neuropathological examination. Neurological examination was normal apart from dystonia and signs referable to prior cryothalamotomy. Workup for metabolic and genetic causes of dystonia was negative. Neuroimaging showed severe bilateral putaminal degeneration, which subsequently correlated with the neuropathological findings of gliosis, spongiform degeneration, and cavitation. The substantia nigra pars compacta contained a normal number of neurons but decreased tyrosine hydroxylase immunoreactivity. There were no histopathological markers of other metabolic or degenerative diseases.

The chorea of McLeod syndrome

Among the movement disorders associated with acanthocytosis, McLeod syndrome (McKusick 314850) is the one that is best characterized on the molecular level. Its defining feature is low reactivity of Kell erythrocyte antigens. This is due to absence of membrane protein KX that forms a complex with the Kell protein. KX is coded for by the XK gene on the X-chromosome. We present six males (aged 29 to 60 years), with proven XK mutations, to discuss the chorea associated with McLeod syndrome. The movement disorder commonly develops in the fifth decade and is progressive. It affects the limbs, the trunk and the face. In addition to facial grimacing, involuntary vocalization can be present. In early stages there may only be some restlessness or slight involuntary distal movements of ankles and fingers. Lip-biting and facial tics seem more common in autosomal recessive choreoacanthocytosis linked to chromosome 9. This, together with the absence of dysphagia in McLeod syndrome, may help in differential diagnosis. Recent findings suggest a role for the endothelin system of the striatum in the pathogenesis of McLeod syndrome.

Progressive pseudobulbar paresis, early choreiform movements, and later rigidity: appearance in two sets of dizygotic twins in the same family

In a family with two sets of dizygotic twins, three, possibly all four, siblings were affected by the same disorder. The parents were unrelated and the illness seemed limited to one generation. Onset was in the early to mid-20s with tics and choreiform movements, dysarthria, and dysphagia. Two twins had epilepsy. There was a marked dyscoordination of bulbar musculature reminiscent of pseudobulbar paresis. Involuntary movements were prominent during the first years, but then disappeared and were replaced by an akinetic-rigid parkinsonian appearance in the late stage. The intellect remained largely intact. Tendon reflexes were reduced. Varying degrees of peripheral nerve changes were seen. Two patients died after 22-24 years from causes indirectly related to the main illness. Marked degenerative changes were found in the caudate nucleus and putamen. Acanthocytes in significant numbers could not be detected in peripheral blood. Lipoproteinelectrophoresis was normal. Creatine kinase levels were moderately raised in one patient, normal in the others. Although certain clinical resemblances exist with neuroacanthocytosis, the exact nosologic status of the disorder has not been determined.

Chorea-acanthocytosis: genetic linkage to chromosome 9q21

Chorea-acanthocytosis (CHAC) is a rare autosomal recessive disorder characterized by progressive neurodegeneration and unusual red-cell morphology (acanthocytosis), with onset in the third to fifth decade of life. Neurological impairment with acanthocytosis (neuroacanthocytosis) also is seen in abetalipoproteinemia and X-linked McLeod syndrome. Whereas the molecular etiology of McLeod syndrome has been defined (Ho et al. 1994), that of CHAC is still unknown. In the absence of cytogenetic rearrangements, we initiated a genomewide scan for linkage in 11 families, segregating for CHAC, who are of diverse geographical origin. We report here that the disease is linked, in all families, to a 6-cM region of chromosome 9q21 that is flanked by the recombinant markers GATA89a11 and D9S1843. A maximum two-point LOD score of 7.1 (theta = .00) for D9S1867 was achieved, and the linked region has been confirmed by homozygosity-by-descent, in offspring from inbred families. These findings provide strong evidence for the involvement of a single locus for CHAC and are the first step in positional cloning of the disease gene.

Epilepsy as the presenting feature of neuroacanthocytosis in siblings

A brother and sister developed epilepsy at the age of 28 and 30 years respectively, and were subsequently found to have neuroacanthocytosis. The brother developed tics, and a tendency to self-mutilate a year later, but his sister had not developed any movement disorder in the 5 years since the onset of epilepsy. In families with epilepsy, the diagnosis of neuroacanthocytosis should be considered, particularly when one family member has tics or other involuntary movements.

Diagnosis of rare dementia syndromes: an algorithmic approach

The etiology of dementia can be diagnosed in most patients using a standard clinical approach consisting of physical, neurologic, and mental status examinations, and laboratory testing, lumbar puncture, and neuroimaging. In some cases, however, the clinical presentation or historical data are unusual, or the results of the workup are inconclusive or atypical. A rare cause of dementia may then be present and a complicated evaluation may be necessary to identify the specific disease process. A potentially useful approach to the diagnosis of rare dementing disorders consists of a series of diagnostic algorithms. This approach utilizes results of neuroimaging studies to guide the evaluation through additional diagnostic steps such as specific enzymatic or immunologic assays or biopsy of extraneural tissues. The disorders potentially detected by these algorithms typically have unusual clinical features such as early age of onset, abnormal neurologic signs and symptoms early in the clinical course, early personality and mood changes, extrapyramidal or cerebellar signs and symptoms, seizures, peripheral neuropathy or myopathy, and extraneural abnormalities involving the dermatologic, cardiovascular, musculoskeletal, or ocular systems. Accurate diagnosis of these rare causes of dementia is important for medical and psychiatric management, prognosis, and genetic counseling.