Developments in neuroacanthocytosis: expanding the spectrum of choreatic syndromes

[Case-report of neuroacanthocytosis associated with a compound mutation in the VPS13A gene]

Neuroacanthocytosis is a group of neurodegenerative diseases manifested by a combition of neurological symptoms (most often choreic hyperkinesis) and the presence of an increased number of acanthocytes (erythrocytes with horns) in the peripheral blood. This group includes chorea-acanthocytosis, MacLeod's syndrome, pantothenate kinase-associated neurodegeneration, Huntington-like disease type 2, and some other very rare diseases. This article presents a genetically confirmed clinical case of chorea-acanthocytosis associated with a compound mutation in the VPS13A gene, discusses in detail the stages of a diagnostic search, presents an algorithm for examining patients with chorea.

Movement disorders in systemic diseases

Movement disorders, classically involving dysfunction of the basal ganglia commonly occur in neurodegenerative and structural brain disorders. At times, however, movement disorders can be the initial manifestation of a systemic disease. In this article we discuss the most common movement disorders which may present in infectious, autoimmune, paraneoplastic, metabolic and endocrine diseases. Management often has to be multidisciplinary involving primary care physicians, neurologists, allied health professionals including nurses, occupational therapists and less frequently neurosurgeons. Recognizing and treating the underlying systemic disease is important in order to improve the neurological symptoms.

Computational identification of phospho-tyrosine sub-networks related to acanthocyte generation in neuroacanthocytosis

Acanthocytes, abnormal thorny red blood cells (RBC), are one of the biological hallmarks of neuroacanthocytosis syndromes (NA), a group of rare hereditary neurodegenerative disorders. Since RBCs are easily accessible, the study of acanthocytes in NA may provide insights into potential mechanisms of neurodegeneration. Previous studies have shown that changes in RBC membrane protein phosphorylation state affect RBC membrane mechanical stability and morphology. Here, we coupled tyrosine-phosphoproteomic analysis to topological network analysis. We aimed to predict signaling sub-networks possibly involved in the generation of acanthocytes in patients affected by the two core NA disorders, namely McLeod syndrome (MLS, XK-related, Xk protein) and chorea-acanthocytosis (ChAc, VPS13A-related, chorein protein). The experimentally determined phosphoproteomic data-sets allowed us to relate the subsequent network analysis to the pathogenetic background. To reduce the network complexity, we combined several algorithms of topological network analysis including cluster determination by shortest path analysis, protein categorization based on centrality indexes, along with annotation-based node filtering. We first identified XK- and VPS13A-related protein-protein interaction networks by identifying all the interactomic shortest paths linking Xk and chorein to the corresponding set of proteins whose tyrosine phosphorylation was altered in patients. These networks include the most likely paths of functional influence of Xk and chorein on phosphorylated proteins. We further refined the analysis by extracting restricted sets of highly interacting signaling proteins representing a common molecular background bridging the generation of acanthocytes in MLS and ChAc. The final analysis pointed to a novel, very restricted, signaling module of 14 highly interconnected kinases, whose alteration is possibly involved in generation of acanthocytes in MLS and ChAc.

Deep brain stimulation of the globus pallidus internal improves symptoms of chorea-acanthocytosis

Chorea-acanthocytosis is a rare autosomal recessive disorder. To date, treatment is only symptomatic and supportive. Results from the few reports of chorea-acanthocytosis patients treated with deep brain stimulation (DBS) have been inconsistent. We present case reports for two patients with chorea-acanthocytosis who received DBS treatment and compare the outcomes with results from the literature. Both patients showed the typical clinical features of chorea-acanthocytosis with motor symptoms resistant to medical treatment. Chorea was significantly improved following low-frequency DBS treatment in both patients. However, dystonia was only mildly improved. Four chorea-acanthocytosis patients treated with DBS treatment have been reported in the literature. One patient had improvement with low-frequency DBS stimulation, while another two had improvement with higher-frequency DBS. One patient, however, did not improve with either low-frequency or high-frequency DBS. Bilateral DBS to the GPi can improve chorea and dystonia in some patients with intractable chorea-acanthocytosis. However, selection criteria for the most promising candidates must be defined, and the long-term benefits evaluated in clinical studies.

Two McLeod patients with novel mutations in XK

McLeod syndrome (MLS) is a rare, X-linked, late-onset, disease involving hematological, brain, and neuromuscular systems, caused by mutations in XK that result in either defective XK or complete loss of XK protein. Acanthocytosis of erythrocytes is a typical feature. We report novel mutations in two patients who exhibited typical clinical characteristics of MLS. The coding and flanking intronic regions of XK were amplified by PCR, sequenced, and compared with the normal XK sequence. XK protein, and its complexed partner protein, Kell, were assessed by Western blot analysis. Patient 1 was found to have a single base insertion, 605insA at 175Ile creating a frame shift within the coding sequence of XK. Patient 2 had a single base substitution in the 3' splice sequence of intron 2 (IVS2-2a>g). In both cases mutations resulted in the absence of XK protein.

The first case report of neuroacanthocytosis in Thailand: utilization of a peripheral blood smear technique for detecting acanthocytes

BACKGROUND

Neuroacanthocytosis (NA) is a heterogeneous group of hereditary syndromes characterized by the association of neurological abnormalities with acanthocytosis. Among those, chorea-acanthocytosis (ChAc) is the most frequent form, manifested by predominant orofacial dyskinesias associated with marked dysarthria and dysphagia.

PURPOSE

To describe the first known case of ChAc in Thailand.

METHODS AND RESULTS

A 40-year-old man presented with "core features" of NA which led to a high level of suspicion of this syndrome. An initial dry blood smear did not reveal acanthocytes but by utilizing diluted blood combined with a wet blood smear, which is accepted as the clinical gold standard when combined with an examination, acanthocytes were detected.

CONCLUSION

Diagnosis of NA is possible without molecular diagnostics by relying on a high degree of clinical suspicion of characteristic clinical features and a standardized wet blood smear method of peripheral blood examination for acanthocytes.

[Chorea-acanthocytosis without acanthocytes]

INTRODUCTION

Chorea-acanthocytosis (ChAc) is one of the neuroacanthocytosis syndromes which form a group of disorders characterized by the association of neurological abnormalities and spiculated red blood cells called acanthocytes. ChAc patients exhibit involuntary movements, psychiatric abnormalities and progressive cognitive deterioration. We report a case of ChAc in which blood smears failed to demonstrate acanthocytes.

CASE REPORT

A 26-year-old man presented since two years with hyperkinetic movements. The family history was non contributive, parents were consanguineous. Neurological examination revealed choreatic hyperkinesia and dystonia, predominant in the orofacial region. Mild cognitive decline and behavior abnormalities were noted with repetitive activities. Brain MRI showed striatal atrophy. Molecular testing for Huntington's disease was negative. Routine biological screening was normal except for elevated CPK and LDH. Copper and ceruloplasmin blood levels were normal, as well as purine metabolism and lipoproteins. Further screening for metabolic diseases showed no significant abnormality. Expression of Kell antigens was normal. In several blood smears no acanthocytes were seen. Electromyographic studies showed slight neuropathic changes. Despite the absence of acanthocytes, chorein western blot was performed on blood samples which revealed an absent or markedly reduced level of chorein in erythrocyte membranes. A mutation of the ChAc gene was thus likely so the diagnosis of ChAc was retained. Genetic studies for VPS13A are pending.

DISCUSSION

ChAc is an autosomal recessive disorder due to mutations of the VPS13A gene coding for chorein. Absence or late appearance of acanthocytes in ChAc has been described in a few case reports. In conclusion ChAc is a rare disorder in which the presence of acanthocytes is not mandatory. In case of doubt, chorein western blot can be useful.

A neuropathological study of autosomal-dominant chorea-acanthocytosis with a mutation of VPS13A

We report the first autopsy case of genetically confirmed, autosomal-dominant chorea-acanthocytosis (AD-ChAc), showing a heterozygous mutation (G-A) at nucleotide position 8,295 in exon 57 of VPS13A. The patient was a 36-year-old Japanese man and the duration of his illness was 11 years. Neuropathologically, the patient showed marked atrophy and neuronal loss, particularly small and medium-sized neurons, with astrocytic gliosis in the caudate nucleus, putamen and globus pallidus. These findings were similar to previous autopsy reports of autosomal-recessive ChAc (AR-ChAc) with mutations of VPS13A. The broad distribution of atrophic neurons and astrocytosis throughout the whole brain was unique in our AD-ChAc patient and has not been described in AR-ChAc. The neuronal density of the dorsal caudate nucleus was lower than that of the ventral side in this patient as well as in three Huntington's disease (HD) patients. The neuronal densities in both the rostral and caudal sides were lower than that in the middle region at the anterior commissure level, while in the three HD patients, the neuronal densities of the caudate nucleus were more decreased in the caudal side. This ChAc patient showed faint immunoreactivity in the caudate nucleus and globus pallidus with antibodies against the striatal neurotransmitters, methionine-enkephalin, leucine-enkephalin and substance P. The difference in patterns of neuronal vulnerability could reflect those in the mechanisms of neurodegeneration between ChAc and HD.

Neuroacanthocytosis and carbamazepine responsive paroxysmal dyskinesias

Neuroacanthocytosis (NA) comprises a genetically heterogeneous group of disorders characterized by dysfunction of the erythrocyte membrane, presenting with acanthocytes and several neurological manifestations. We report the case of a 42-year-old woman with NA who in addition had episodes consistent with paroxysmal dyskinesias. She was diagnosed with NA featuring mild chorea, weakness of the right lower extremity and myoclonic jerks. However, one year after onset she presented attacks of paroxysmal abnormal movements, consistent with paroxysmal kinesigenic dyskinesias. Carbamazepine markedly reduced the frequency and severity of the attacks. Our case illustrates that paroxysmal dyskinesias can be a hitherto unrecognized manifestation of neuroacanthocytosis responsive to carbamazepine.

Neurologic phenotypes associated with acanthocytosis

The term "neuroacanthocytosis" is normally used to refer to autosomal recessive chorea-acanthocytosis and X-linked McLeod syndrome, but there are other movement disorders in which erythrocyte acanthocytosis may also be seen, such as Huntington disease-like 2 and pantothenate kinase-associated neurodegeneration. Disorders of serum lipoproteins such as Bassen-Kornzweig disease form a distinct group of neuroacanthocytosis syndromes in which ataxia is observed, but movement disorders are not seen. Genetic testing has enabled us to distinguish between these disorders, even when there are considerable similarities between phenotypes. Improved detection is important for accurate genetic counseling, for monitoring for complications, and, it is hoped, for implementing causal treatments, once these become available. As in other neurodegenerative conditions, animal models are a promising strategy for the development of such therapies.