Neuroacanthocytosis masquerading as Huntington's disease: CT/MRI findings

Neuronal Dysfunction in iPSC-Derived Medium Spiny Neurons from Chorea-Acanthocytosis Patients Is Reversed by Src Kinase Inhibition and F-Actin Stabilization

Chorea-acanthocytosis (ChAc) is a fatal neurological disorder characterized by red blood cell acanthocytes and striatal neurodegeneration. Recently, severe cell membrane disturbances based on depolymerized cortical actin and an elevated Lyn kinase activity in erythrocytes from ChAc patients were identified. How this contributes to the mechanism of neurodegeneration is still unknown. To gain insight into the pathophysiology, we established a ChAc patient-derived induced pluripotent stem cell model and an efficient differentiation protocol providing a large population of human striatal medium spiny neurons (MSNs), the main target of neurodegeneration in ChAc. Patient-derived MSNs displayed enhanced neurite outgrowth and ramification, whereas synaptic density was similar to controls. Electrophysiological analysis revealed a pathologically elevated synaptic activity in ChAc MSNs. Treatment with the F-actin stabilizer phallacidin or the Src kinase inhibitor PP2 resulted in the significant reduction of disinhibited synaptic currents to healthy control levels, suggesting a Src kinase- and actin-dependent mechanism. This was underlined by increased G/F-actin ratios and elevated Lyn kinase activity in patient-derived MSNs. These data indicate that F-actin stabilization and Src kinase inhibition represent potential therapeutic targets in ChAc that may restore neuronal function.

SIGNIFICANCE STATEMENT

Chorea-acanthocytosis (ChAc) is a fatal neurodegenerative disease without a known cure. To gain pathophysiological insight, we newly established a human in vitro model using skin biopsies from ChAc patients to generate disease-specific induced pluripotent stem cells (iPSCs) and developed an efficient iPSC differentiation protocol providing striatal medium spiny neurons. Using patch-clamp electrophysiology, we detected a pathologically enhanced synaptic activity in ChAc neurons. Healthy control levels of synaptic activity could be restored by treatment of ChAc neurons with the F-actin stabilizer phallacidin and the Src kinase inhibitor PP2. Because Src kinases are involved in bridging the membrane to the actin cytoskeleton by membrane protein phosphorylation, our data suggest an actin-dependent mechanism of this dysfunctional phenotype and potential treatment targets in ChAc.

Hereditary chorea - what else to consider when the Huntington's disease genetics test is negative?

Chorea, cognitive, behavioural and psychiatric disturbance occur in varying combinations in Huntington's disease (HD). This is often easy to recognise particularly in the presence of an autosomal dominant history. Whilst HD may be the most common aetiology of such a presentation, several HD phenocopies should be considered if genetic testing for HD is negative. We searched PubMed and the Cochrane Database from January 1, 1946 up to January 1, 2016, combining the search terms: 'chorea', 'Huntington's disease', 'HDL' and 'phenocopies'. HD phenocopies frequently display additional movement disorders such as myoclonus, dystonia, parkinsonism and tics. Here, we discuss the phenotypes, and investigations of HD-like disorders where the combination of progressive chorea and cognitive impairment is obvious, but HD gene test result is negative. Conditions presenting with sudden onset chorea such as vascular, infectious and autoimmune causes are not the primary focus of our discussion, but we will make a passing reference to these as some of these conditions are potentially treatable. Hereditary forms of chorea are a heterogeneous group of conditions and this number is increasing. While most of these conditions are not curable, molecular genetic testing has enabled many of these disorders to be distinguished from HD. Getting a precise diagnosis may enable patients and their families to better understand the nature of their condition.

FDG PET brain scan demonstrated glucose hypometabolism of bilateral caudate nuclei and putamina in a patient with chorea-acanthocytosis

Chorea-acanthocytosis is 1 type of neuroacanthocytosis that is a group of rare, hereditary neurodegenerative disorders. We presented a brain FDG PET finding of a 31-year-old woman with chorea-acanthocytosis. The images demonstrated significant hypometabolism in bilateral caudate nuclei and putamina. The finding of FDG PET is more prominent than that of MRI. Another interesting observation is the mildly increased FDG uptake in pituitary gland, although its relationship with the disease is unclear.

Deep brain stimulation in the treatment of chorea

Deep brain stimulation has been used as a means of reducing dyskinesias in various conditions, including Parkinson's disease and dystonia for many years. Recently, owing to the clinical similarities between L-dopa induced dyskinesia and chorea, deep brain stimulation has now been implemented as a novel treatment method in both Huntington's disease and neuroacanthocytosis, and a paucity of case studies exist reporting its efficacy. This review will summarize the case studies of deep brain stimulation in both Huntington's disease and neuroacanthocytosis, and discuss the possible implications and limitations associated with these reports. As both these disorders are often refractory to medication and difficult to treat, deep brain stimulation may be a useful treatment option in the future.

Shape alterations in the striatum in chorea-acanthocytosis

Chorea-acanthocytosis (ChAc) is an uncommon autosomal recessive disorder due to mutations of the VPS13A gene, which encodes for the membrane protein chorein. ChAc presents with progressive limb and orobuccal chorea, but there is often a marked dysexecutive syndrome. ChAc may first present with neuropsychiatric disturbance such as obsessive-compulsive disorder (OCD), suggesting a particular role for disruption to striatal structures involved in non-motor frontostriatal loops, such as the head of the caudate nucleus. Two previous studies have suggested a marked reduction in volume in the caudate nucleus and putamen, but did not examine morphometric change. We investigated morphometric change in 13 patients with genetically or biochemically confirmed ChAc and 26 age- and gender-matched controls. Subjects underwent magnetic resonance imaging and manual segmentation of the caudate nucleus and putamen, and shape analysis using a non-parametric spherical harmonic technique. Both structures showed significant and marked reductions in volume compared with controls, with reduction greatest in the caudate nucleus. Both structures showed significant shape differences, particularly in the head of the caudate nucleus. No significant correlation was shown between duration of illness and striatal volume or shape, suggesting that much structural change may have already taken place at the time of symptom onset. Our results suggest that striatal neuron loss may occur early in the disease process, and follows a dorsal-ventral gradient that may correlate with early neuropsychiatric and cognitive presentations of the disease.

Caudate atrophy on MRI is a characteristic feature of FTLD-FUS

BACKGROUND AND PURPOSE

Frontotemporal lobar degeneration (FTLD) can be subdivided into those in which the abnormal protein is tau (FTLD-TAU), the TAR DNA binding protein 43 (FTLD-TDP) and the fused in sarcoma protein (FTLD-FUS). We have observed severe caudate atrophy at autopsy in FTLD-FUS, and hence, we aimed to determine whether caudate atrophy on MRI is a feature that can distinguish FTLD-FUS from FTLD-TDP and FTLD-TAU.

METHODS

From a cohort of 207 cases of FTLD, we identified all cases of FTLD-FUS that had a volumetric antemortem head MRI (n = 3). Caudate and frontal lobe volumes were measured in all three cases using atlas-based parcellation and SPM5 and were compared to 10 randomly selected cases of FTLD-TDP and 10 randomly selected cases of FTLD-TAU. Total grey matter volumes were also calculated for all cases.

RESULTS

The FTLD-FUS cases had significantly smaller caudate volumes (P = 0.02) yet similar frontal lobe grey matter volumes (P = 0.12) compared to FTLD-TDP and FTLD-TAU. Caudate volumes when corrected for total grey matter volume (P = 0.01) or frontal lobe grey matter volume (P = 0.01) were significantly smaller in FTLD-FUS than in FTLD-TDP and FTLD-TAU and showed no overlap with the other two groups.

CONCLUSIONS

Caudate atrophy on MRI appears to be significantly greater in FTLD-FUS compared with FTLD-TDP and FTLD-TAU, suggesting that severe caudate atrophy may be a useful clinical feature to predict FTLD-FUS pathology.

Demonstration of cerebellar atrophy in neuroacanthocytosis of 2 siblings

SUMMARY

Neuroacanthocytosis is a rare hereditary disorder characterized by involuntary choreiform movements and erythrocytic acanthocytosis in the peripheral blood. Clinical manifestations of this disorder resemble those of Huntington disease (HD). Neuroimaging features of neuroacanthocytosis are atrophy and signal intensity change of the striata on MR imaging, as in HD. We report herein the cases of 2 siblings with neuroacanthocytosis showing cerebellar atrophy as well as atrophy and signal intensity changes of striata.

Head of the caudate nucleus is most vulnerable in chorea-acanthocytosis: a voxel-based morphometry study

Chorea-acanthocytosis (ChAc; OMIM 200150) is a rare autosomal recessive disease with dysfunction of the erythrocyte membrane, presenting with acanthocytes and neurological manifestations characterized by progressive hyperkinesias (chorea, dystonia) and neuropsychological impairment. Damage to the basal ganglia was described previously in neuropathological and neuroimaging investigations. We analyzed high-resolution MRI of six ChAc patients with mutations in the VPS13A gene (median age, 37 years; mean time since clinical onset, 13 years) with respect to regional atrophy by use of the observer-independent technique of voxel-based morphometry in comparison to 15 age-matched healthy controls. Additionally, global brain atrophy was determined using the standardized brain parenchymal fraction (BPF) method. A robust regional reduction of gray matter density was observed in the head of the caudate nucleus bilaterally and was nearly symmetrical (P < 0.001, corrected for small volumes). No additional gray matter changes were found. In the BPF analysis, there was no significant global brain atrophy. The predilection of atrophy in the head of the caudate nucleus, as suggested by our results, argues for a particular vulnerability of this part of the striatum in ChAc and is in agreement with pronounced neuropsychological disturbances that are thought to rely on these regions.

Chorea-acanthocytosis: A Mimicker of Huntington Disease Case Report and Review of the Literature

BACKGROUND

Neuroacanthocytosis consists of a group of rare heterogeneous neurodegenerative disorders associated with acanthocytosis. Chorea-acanthocytosis, a variety of neuroacanthocytosis, is an autosomal recessive condition with clinical and radiologic features similar to Huntington disease. Although difficult, distinguishing between these entities is crucial as the implications for genetic counseling are significant.

REVIEW SUMMARY

We report the case of a 33-year-old female who presented to our institution with a 3-year history of chorea. The patient's prominent orofacial symptoms and the presence of acanthocytes on peripheral blood smear led to the correct diagnosis of chorea-acanthocytosis.

CONCLUSIONS

The significant similarities between chorea-acanthocytosis and Huntington disease at the clinical and radiologic levels can lead to an initial misdiagnosis. Clinical clues suggestive of chorea-acanthocytosis include prominent orofacial dyskinesias, often causing dysarthria and dysphagia. Acanthocytosis, when present on peripheral blood smear, can confirm the diagnosis.

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.

Neuroacanthocytosis misdiagnosed as Huntington's disease: a case report

A patient with the typical features of neuroacanthocytosis is reported. Chorea, tics, personality changes and caudate atrophy on cranial MRI resulted in an erroneous diagnosis of Huntington's disease elsewhere. Attention to other features viz., absence of ocular motility disturbances, amyotrophy, areflexia, EMG evidence of axonopathy, raised serum creatinine phosphokinase (CPK) levels and the typical erythrocytic acanthocytosis enabled us to establish the correct diagnosis. The typical features of the disease as seen in the patient are discussed. In view of the implications for genetic counseling, careful clinical and laboratory evaluation is always warranted to exclude neuroacanthocytosis in all suspected cases of Huntington's disease.

A conserved sorting-associated protein is mutant in chorea-acanthocytosis

Chorea-acanthocytosis (CHAC, MIM 200150) is an autosomal recessive neurodegenerative disorder characterized by the gradual onset of hyperkinetic movements and abnormal erythrocyte morphology (acanthocytosis). Neurological findings closely resemble those observed in Huntington disease. We identified a gene in the CHAC critical region and found 16 different mutations in individuals with chorea-acanthocytosis. CHAC encodes an evolutionarily conserved protein that is probably involved in protein sorting.