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Background: McLeod syndrome (MLS) is an X-linked multisystemic progressive disorder caused by loss of function mutations in the XK gene. The rare blood group phenotype of MLS patients with absent Kx antigen requires the support of specialized transfusion institutions because of the risk of transfusion complications. Acanthocytosis of red blood cells occurs in almost all patients. Nonhematological manifestations of MLS are very similar to those of VPS13A disease (chorea-acanthocytosis), an autosomal-recessive condition. Their shared phenotype apart from acanthocytosis includes movement disorders such as chorea and dystonia, epilepsy, peripheral neuropathy, and muscle involvement, typically with creatine kinase (CK) elevation, cardiomyopathy included. Summary: In this review, we describe the nonhematological manifestations of MLS in comparison with those of VPS13A disease. While there are many similarities, differences such as mode of inheritance, sex distribution, age at manifestation, severity of heart involvement, frequency of feeding dystonia or of involuntary head drops may help to distinguish these disorders in the clinic. Immunohematological demonstration of the McLeod-Kell phenotype or detection of pathogenic mutations of XK (or VPS13A, respectively) is the gold standard for distinction. “Neuroacanthocytosis” was often used as an overarching term, but is potentially misleading, as the term does not refer to a defined disease entity. Its use, if continued, must not prevent clinicians to seek a final diagnosis on the basis of molecular findings. The clinical similarity of MLS and VPS13A disease has long suggested some shared pathophysiology. Evidence for molecular interaction between XK, the McLeod protein, and chorein, the VPS13A gene product, has recently been put forward: XK forms a complex with chorein/VPS13A, a bulk lipid transporter located at various membrane contact sites. The exact role of XK in this complex needs to be further elucidated. Impairment of bulk lipid transport appears as the common denominator of both MLS and VPS13A disease. A variety of further conditions may in time be added to the “bulk lipid transport diseases,” such as the recently recognized disorders caused by mutations in the VPS13B, VPS13C, and VPS13D genes. Key Messages: (1) Patients diagnosed with the rare red cell McLeod phenotype (McLeod syndrome, MLS) require interdisciplinary collaboration of transfusion medicine specialists, neurologists, and cardiologists for both their hematological and nonhematological disease manifestations. (2) The phenotypical similarity of MLS and VPS13A disease, often leading to either confusion or insufficient diagnostic depth (under the label of “neuroacanthocytosis”), is based on interaction of the respective proteins, XK and chorein, within the cellular machinery for bulk lipid transport. (3) Overall, the term “bulk lipid transport diseases” seems useful for further research on a group of conditions that may not only share pathophysiology, but may also share treatment approaches.

The peroxiredoxins (PRXs) constitute a ubiquitous antioxidant. Growing evidence in neurodegenerative disorders such as Parkinson’s disease (PD) or Alzheimer’s disease (AD) has highlighted a crucial role for PRXs against neuro-oxidation. Chorea-acanthocytosis/Vps13A disease (ChAc) is a devastating, life-shortening disorder characterized by acanthocytosis, neurodegeneration and abnormal proteostasis. We recently developed a Vps13a−/− ChAc-mouse model, showing acanthocytosis, neurodegeneration and neuroinflammation which could be restored by LYN inactivation. Here, we show in our Vps13a−/− mice protein oxidation, NRF2 activation and upregulation of downstream cytoprotective systems NQO1, SRXN1 and TRXR in basal ganglia. This was associated with upregulation of PRX2/5 expression compared to wild-type mice. PRX2 expression was age-dependent in both mouse strains, whereas only Vps13a−/− PRX5 expression was increased independent of age. LYN deficiency or nilotinib-mediated LYN inhibition improved autophagy in Vps13a−/− mice. In Vps13a−/−; Lyn−/− basal ganglia, absence of LYN resulted in reduced NRF2 activation and down-regulated expression of PRX2/5, SRXN1 and TRXR. Nilotinib treatment of Vps13a−/− mice reduced basal ganglia oxidation, and plasma PRX5 levels, suggesting plasma PRX5 as a possible ChAc biomarker. Our data support initiation of therapeutic Lyn inhibition as promptly as possible after ChAc diagnosis to minimize development of irreversible neuronal damage during otherwise inevitable ChAc progression.

Introduction We aimed to study the various cardiac manifestations of the two core neuroacanthocytosis (NA) syndromes, namely chorea-acanthocytosis (ChAc) and McLeod syndrome (MLS). So far, cardiac involvement has been described as specific feature only for MLS. Methods We studied six patients with ChAc (mean age 44.5 years, five men, one woman) and six patients with MLS (mean age 57.1 years, all men). Cardiac evaluation included echocardiography and/or cardiac magnetic resonance imaging (cardiac MRI), 24-h ECG-recording and examination of cardiac biomarkers. Results Cardiac involvement of ChAc was found in four of six patients. Two patients showed mildly reduced left ventricular ejection fraction (LVEF), two other patients mild to moderate left ventricular (LV) dilatation. Neither an increase in ventricular ectopic beats nor ventricular tachycardia were evident in ChAc. Four of five MLS patients showed left ventricle dilatation and reduced left ventricular ejection fraction (LVEF). Two of these, in addition, had critical ventricular tachycardia. High sensitive troponin T was elevated in all patients, for whom data were available (n = 10). In contrast, elevation of high sensitive troponin I was found in one of six ChAc and one of two MLS patients. Conclusion For the first time, we reveal cardiac involvement in a cohort of six ChAc patients, while the risk to develop heart failure seems lower than in MLS. Our study confirms the malignant nature of MLS in terms of ventricular arrhythmias and progression to advanced heart failure. Herein, we define disease-specific recommendations for cardiac assessment in both conditions.

Introduction Chorea-acanthocytosis (ChAc) is a rare hereditary neurodegenerative disease, characterized by hyper- and hypokinetic movement disorders, peripheral neuropathy and acanthocytosis. Biomarkers are not established; possible candidates include neurofilament reflecting neuroaxonal damage. Methods We studied serum neurofilament light chain (sNfL) of six ChAc patients compared to two healthy control cohorts (A, six age/sex matched and B, historical cohort of 59 healthy adult subjects) and in two patients with the very similar condition of McLeod syndrome (MLS), the second core syndrome of neuroacanthocytosis. sNfL was quantified using single-molecule array analysis. Results sNfL concentration was significantly higher in the ChAc cohort (18.73 pg/ml; IQR 15.65–27.70) compared to both healthy control cohorts (A, 7.37 pg/ml; IQR 5.60–9.05; B, 3.10 pg/ml; IQR 2.43–3.98). In MLS patients, a similar sNfL increase was observed. Conclusions sNfL is significantly increased in ChAc and MLS and seems to reflect neuroaxonal damage in the peripheral as well as the central nervous system.

Background McLeod syndrome (MLS) is an ultra-rare neurodegenerative X-linked disease caused by mutations in the XK gene, classified as one of the core neuroacanthocytosis syndromes. Together with the clinically very similar chorea-acanthocytosis it belongs to the heterogeneous group of ‘Huntington’s disease (HD) phenocopies’. Aims To characterize a cohort of HD phenocopies with the genetically confirmed diagnosis of McLeod syndrome. Methods This is a retrospective and prospective analysis of genotype and phenotype of sixteen McLeod cases. Results We longitudinally characterized the second largest cohort known to date. We identified novel XK mutations as well as deletions that extend into the PRRG1 gene (novel) and describe two contiguous gene deletion cases of MLS with X-linked chronic granulomatous disease (deletion also effecting the CYBB gene). This study confirms core features of MLS such as late onset hyperkinetic movements in association with neuro/myopathy, neuropsychiatric impairment, cardiac involvement, hyperCKemia. Novel aspects in this MLS series seem obstructive sleep apnea and epileptic seizure onset in childhood. Conclusions Our study expands the limited knowledge on the variable course, the various clinical manifestations and the genetic spectrum of a hereditary HD phenocopy syndrome.

(1) Background: Chorea-acanthocytosis and McLeod syndrome are the core diseases among the group of rare neurodegenerative disorders called neuroacanthocytosis syndromes (NASs). NAS patients have a variable number of irregularly spiky erythrocytes, so-called acanthocytes. Their detection is a crucial but error-prone parameter in the diagnosis of NASs, often leading to misdiagnoses. (2) Methods: We measured the standard Westergren erythrocyte sedimentation rate (ESR) of various blood samples from NAS patients and healthy controls. Furthermore, we manipulated the ESR by swapping the erythrocytes and plasma of different individuals, as well as replacing plasma with dextran. These measurements were complemented by clinical laboratory data and single-cell adhesion force measurements. Additionally, we followed theoretical modeling approaches. (3) Results: We show that the acanthocyte sedimentation rate (ASR) with a two-hour read-out is significantly prolonged in chorea-acanthocytosis and McLeod syndrome without overlap compared to the ESR of the controls. Mechanistically, through modern colloidal physics, we show that acanthocyte aggregation and plasma fibrinogen levels slow down the sedimentation. Moreover, the inverse of ASR correlates with the number of acanthocytes (R2=0.61, p=0.004). (4) Conclusions: The ASR/ESR is a clear, robust and easily obtainable diagnostic marker. Independently of NASs, we also regard this study as a hallmark of the physical view of erythrocyte sedimentation by describing anticoagulated blood in stasis as a percolating gel, allowing the application of colloidal physics theory.

BackgroundChorea-acanthocytosis (ChAc) is a neurodegenerative disease caused by mutations in the VPS13A gene. It is characterized by several neurological symptoms and the appearance of acanthocytes. Elevated tyrosine kinase Lyn activity has been recently identified as one of the key pathophysiological mechanisms and therefore represents a promising drug target.MethodsWe evaluated an individual off-label treatment with the FDA-approved tyrosine kinase inhibitor dasatinib (100 mg/d, 25.8-50.4 weeks) of three ChAc patients. Alongside with a thorough safety monitoring, we assessed motor and non-motor scales (e.g. MDS-UPDRS, UHDRS, quality of life) as well as routine and experimental laboratory parameters (e.g. serum neurofilament, Lyn kinase activity, actin cytoskeleton in red blood cells).ResultsDasatinib appeared to be reasonably safe. The clinical parameters remained stable without significant improvement or deterioration. Regain of deep tendon reflexes was observed in one patient. Creatine kinase, serum neurofilament levels and acanthocyte count did not reveal consistent effects. However, reduction of initially elevated Lyn kinase activity and accumulated autophagy markers as well as partial restoration of actin cytoskeleton was found in red blood cells.DiscussionWe report on the first treatment approach with disease-modifying intention in ChAc. The experimental parameters indicate target engagement in red blood cells, while clinical effects on the central nervous system could not be proven within a rather short treatment time. Limited knowledge on the natural history of ChAc and the lack of appropriate biomarkers remain major barriers for “clinical trial readiness”. Here, we suggest a panel of outcome parameters for future clinical trials in ChAc.

Chorea-Acanthocytosis (ChAc) is a devastating, little understood, and currently untreatable neurodegenerative disease caused by VPS13A mutations. Based on our recent demonstration that accumulation of activated Lyn tyrosine kinase is a key pathophysiological event in human ChAc cells, we took advantage of Vps13a−/− mice, which phenocopied human ChAc. Using proteomic approach, we found accumulation of active Lyn, γ-synuclein and phospho-tau proteins in Vps13a−/− basal ganglia secondary to impaired autophagy leading to neuroinflammation. Mice double knockout Vps13a−/− Lyn−/− showed normalization of red cell morphology and improvement of autophagy in basal ganglia. We then in vivo tested pharmacologic inhibitors of Lyn: dasatinib and nilotinib. Dasatinib failed to cross the mouse brain blood barrier (BBB), but the more specific Lyn kinase inhibitor nilotinib, crosses the BBB. Nilotinib ameliorates both Vps13a−/− hematological and neurological phenotypes, improving autophagy and preventing neuroinflammation. Our data support the proposal to repurpose nilotinib as new therapeutic option for ChAc patients.

Chorea-acanthocytosis (ChAc) and McLeod syndrome (MLS) are the core diseases among the group of rare neurodegenerative disorders that comprise neuroacanthocytosis syndrome (NAS). Both ChAc and MLS patients present with an increased number of irregularly spiky erythrocytes, so-called acanthocytes. The detection of acanthocytes is often a crucial parameter in the diagnosis of NAS. However, this approach is error-prone and not very reliable, typically explaining the misdiagnosis of NAS patients. Based on the standard Westergren method, we show that compared with that in healthy controls, the erythrocyte sedimentation rate (ESR) with a two-hour read-out is significantly prolonged in ChAc and MLS with no overlap. Thus, the ESR is a clear, robust and easily obtained diagnostic marker. Mechanistically, by applying modern colloidal physics, we show that acanthocyte aggregation and plasma fibrinogen levels slow the sedimentation process. Apart from its diagnostic value, ESR may also be the first biomarker for monitoring treatments for NAS patients. Further studies are required to test whether the ESR may also detect other NASs. In addition to medical progress, this study is also a hallmark of the physical view of the erythrocyte sedimentation process by describing anticoagulated blood in stasis as a percolating gel, allowing the application of colloidal physics theory.

MDS‐criteria for clinical diagnosis of progressive supranuclear palsy (PSP) were recently published, their usability in a classical clinical setting is yet unknown. We retrospectively applied the new criteria using PSP patients’ case files. Assignment of PSP diagnosis according to the MDS‐criteria was possible in 57/80 cases. The main difference to former specialist classification was a lower phenotype diversity and higher representation of PSP‐RS. Furthermore, we examined those patients’ brain MRIs. While neuroradiologists’ reports were suggestive of PSP only in 11/62, the analysis of a blinded rater revealed pathological midbrain‐to‐pons‐ratio in 40/62 implying this imaging feature is often missed.

The 9th International Meeting on Neuroacanthocytosis Syndromes was held on March 23th–25th, 2018 in Dresden, Germany. The conference followed the tradition of the previous eight international symposia, the last of which was held in Ann Arbor, USA in May, 2016. Following the positive response to the previous meeting, a major component of this year’s symposium was the participation of patients, their families, and caregivers. The conference focused primarily on chorea-acanthocytosis as one of the “core” diseases of neuroacanthocytosis syndromes, with some discussion also of McLeod syndrome. These neurodegenerative diseases lead to chorea, epilepsy, cognitive and behavioral problems, and acanthocytosis of red blood cells. While chorea-acanthocytosis is caused by mutations in the VPS13A gene, other “VPS13opathies” (VPS13B-D) were also topic of the meeting. At present there are no treatments that can halt or slow down the progression of these diseases. However, two pathways seem to be prominently involved in chorea-acanthocytosis – namely the PI3K (phosphoinositide 3-kinase) pathway and the Lyn kinase pathway – both of which are potential “druggable” targets. Model organisms including Dictyostelium, Drosophila, yeast, and mice, and human cell models were presented. Finally, clinical translation and clinical trial readiness in such a rare disease were extensively discussed., Tremor and Other Hyperkinetic Movements, Tremor and Other Hyperkinetic Movements

Amyotrophic lateral sclerosis (ALS) is a fatal disorder characterized by degeneration of the upper and lower motor neuron. Among the at least 25 known genes associated with familial (hereditary) and sporadic ALS, mutations in fused-in-sarcoma (FUS) and superoxide dismutase 1 (SOD1) have been extensively investigated in the past years, with emphasis on altered excitability of affected neurons. Recently, we reported on hypoexcitability and increased cell death in a FUS/SOD1-ALS-induced pluripotent stem cell-derived motor neuron model, which was partly reversible by a treatment with the potassium channel blocker 4-aminopyridine (4-AP). Based on this study, we aimed to examine this US Food and Drug Administration-approved drug as a potential individualized treatment for patients with ALS. We therefore retrospectively investigated 4 FUS/SOD1-ALS patients who were prescribed 4-AP. Two patients expressed an improved quality of life due to regain of facial muscle motor function and decreased disease progression rate, respectively. Together with recent pathophysiologic findings, this case series supports the need for clinical trials to examine the efficacy of this potential treatment in distinct ALS subgroups and disease stages.

Annals of Clinical and Translational Neurology 6(12), 2384-2394 (2019). doi:10.1002/acn3.50930, Published by Wiley, Chichester [u.a.]

Neuroacanthocytosis (NA) syndromes are a group of rare diseases characterized by neurological disorders and misshaped spiky red blood cells (acanthocytes) including Chorea-Acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington disease-like 2 (HDL 2), pantothenate kinase-associated neurodegeneration (PKAN), abeta- and hypobetalipoproteinemia and aceruloplasminemia. This clinically and genetically heterogeneous group of diseases shares main clinical features presenting most often as a hyperkinetic movement disorder. Even though these are long noted disease conditions, we still know only little on the underlying disease mechanisms. The current review focuses upon ChAc as the core entity of NA syndromes caused by mutations in the VPS13A gene. The support of patient organizations and the ERA-NET initiative yielded to different multidisciplinary efforts with significant progress on our understanding of ChAc. Disturbances in two pathways are currently considered to be significantly involved in the pathophysiology of ChAc, namely elevated Lyn kinase phosphorylation and decreased signaling via Phosphoinositide 3-kinase (PI3K). These recent developments may reveal potential drugable targets for causative therapies of ChAc.

Introduction: Muscle spindles are crucial for neuronal regulation of striated muscles, but their presence and involvement in the superficial perineal muscles is not known. Methods: Bulbospongiosus and ischiocavernosus muscle specimens were obtained from 31 human cadavers. Serial sections were stained with hematoxylin and eosin, Sirius red, antibodies against Podocalyxin, myosin heavy chain isoforms (MyHC-slow tonic, S46; MyHC-2a/2x, A4.74), and neurofilament for the purpose of muscle spindle screening, counting, and characterization. Results: A low but consistent number of spindles were detected in both muscles. The muscles contained few intrafusal fibers, but otherwise showed normal spindle morphology. The extrafusal fibers of both muscles were small in diameter. Conclusions: The presence of muscle spindles in bulbospongiosus and ischiocavernosus muscles supports physiological models of pelvic floor regulation and may provide a basis for further clinical observations regarding sexual function and micturition. The small number of muscle spindles points to a minor level of proprioceptive regulation. Muscle Nerve 52: 55–62, 2015

The aim of the present study was to demonstrate the location of the different members of the caveolin (cav) family in human muscle spindles. Twenty spindles of three human muscles (vastus medialis, ischiocavernosus, bulbospongiosus) from 12 cadavers were immunohistochemically stained for cav-1, cav-2, and cav-3, and the equatorial and polar regions evaluated. All layers of the outer and inner spindle capsule and all blood vessels within the spindle stained for cav-1 and cav-2. In the muscle spindle, intrafusal muscle fibres stained selectively for cav-3, but with a patchy appearance. Caveolinopathies may therefore also include changes in muscle spindle function.

The aim of the present study was to investigate the presence of sympathetic innervation in human muscle spindles, using antibodies against neuropeptide Y (NPY), NPY receptors and tyrosine hydroxylase (TH). A total of 232 muscle spindles were immunohistochemically examined. NPY and NPY receptors were found on the intrafusal fibers, on the blood vessels supplying muscle spindles and on free nerve endings in the periaxial space. TH-immunoreactivity was present mainly in the spindle nerve and vessel. This is, to our knowledge, the first morphological study concerning the sympathetic innervation of the human muscle spindles. The results provide anatomical evidence for direct sympathetic innervation of the intrafusal fibers and show that sympathetic innervation is not restricted to the blood vessels supplying spindles. Knowledge about direct sympathetic innervation of the muscle spindle might expand our understanding of motor and proprioceptive dysfunction under stress conditions, for example, chronic muscle pain syndromes.

Muscle spindles are crucial for neuronal regulation of striated muscles, but their presence and involvement in the superficial perineal muscles is not known.Bulbospongiosus and ischiocavernosus muscle specimens were obtained from 31 human cadavers. Serial sections were stained with hematoxylin and eosin, Sirius red, antibodies against Podocalyxin, myosin heavy chain isoforms (MyHC-slow tonic, S46; MyHC-2a/2x, A4.74), and neurofilament for the purpose of muscle spindle screening, counting, and characterization.A low but consistent number of spindles were detected in both muscles. The muscles contained few intrafusal fibers, but otherwise showed normal spindle morphology. The extrafusal fibers of both muscles were small in diameter.The presence of muscle spindles in bulbospongiosus and ischiocavernosus muscles supports physiological models of pelvic floor regulation and may provide a basis for further clinical observations regarding sexual function and micturition. The small number of muscle spindles points to a minor level of proprioceptive regulation.

The bulbospongiosus muscle is part of the superficial muscular layer of the perineum and pelvic floor. Its morphology remains controversial in the literature. Therefore, we reinvestigated the fascial arrangement and fiber courses of the bulbospongiosus muscle and its topographical relation to the external anal sphincter.The perineum was dissected in 9 male cadavers (mean ± SD age 78.3 ± 10.7 years). Select samples were obtained for histology and immunohistochemistry. In 43 patients (mean age 60.7 ± 12 years) the topographical relation between the bulbospongiosus muscle and the external anal sphincter was determined by magnetic resonance imaging.The perineum contains several fascial layers consisting of elastic and collagen fibers as well as bundles of smooth muscle cells. The bulbospongiosus muscle was subdivided into a ventral and dorsal portion, which developed in 4 variants. The ventral insertion formed a morphological unity with the ischiocavernous muscle while the dorsal origin had a variable relation to the external anal sphincter (5 variants). A muscle-like or connective tissue-like connection was frequently present between the muscles. However, in some cases the muscles were completely separated.We suggest a concept of variations of bulbospongiosus muscle morphology that unifies the conflicting literature. Its ventral fiber group and the ischiocavernosus muscle form a functional and morphological unity. While the bulbospongiosus muscle and the external anal sphincter remain independent muscles, their frequent connection might have clinical implications for perineal surgery and anogenital disorders.