Hereditary motor and sensory neuropathy associated with cerebellar atrophy (HMSNCA): a new disease

Case report: A novel APTX p.Ser168GlufsTer19 mutation in a Chinese family with ataxia with oculomotor apraxia type 1

Ataxia with oculomotor apraxia type 1 (AOA1) is a rare genetic disorder and is inherited in an autosomal recessive manner. It is mainly characterized by childhood-onset progressive cerebellar ataxia, with dysarthria and gait disturbance being the two most common and typical manifestations. Axonal sensorimotor peripheral neuropathy, dystonia, chorea, and cognitive impairment are common associated symptoms, as are hypoalbuminemia and hypercholesterolemia. Oculomotor apraxia (OMA)has been reported to be a feature often, although not exclusively, associated with AOA1. The Aprataxin gene, APTX, is ubiquitously expressed, and numerous APTX mutations are associated with different clinical phenotypes have been found. In the present study, we enrolled a 14-year-old boy who developed ataxia with staggering gait from the age of 4 years. Early-onset cerebellar ataxia, peripheral axonal neuropathy, cognitive impairment and hypoalbuminemia, hypercholesterolemia were presented in this patient, except for OMA. We applied ataxia-related genes filtering strategies and whole-exome sequencing (WES) to discover the genetic factors in a Chinese family. Sanger sequencing was used in the co segregation analysis in the family members. A compound heterozygous mutation in APTX gene (c.739C>T and c.501dupG) was identified. This is the first description of a genetically confirmed patient of AOA1 in a Chinese family in addition to a novel mutation of c.501dupG in APTX.

Identification of APTX disease-causing mutation in two unrelated Jordanian families with cerebellar ataxia and sensitivity to DNA damaging agents

Background

Ataxia with oculomotor apraxia type 1 (AOA1) is a rare autosomal recessive cerebellar ataxia, caused by mutations in the APTX gene. The disease is characterized by early-onset cerebellar ataxia, oculomotor apraxia and severe axonal polyneuropathy. The aim of this study was to detect the disease-causing variants in two unrelated consanguineous Jordanian families with cerebellar ataxia using whole exome sequencing (WES), and to correlate the identified mutation(s) with the clinical and cellular phenotypes.

Methods

WES was performed in three affected individuals and segregation analysis of p.W279* APTX candidate variant was performed. Expression levels of APTX were measured in patients’ skin fibroblasts and peripheral blood mononuclear cells, followed by western blot analysis in skin fibroblasts. Genotoxicity assay was performed to detect the sensitivity of APTX mutated cells to H₂O₂, MMC, MMS and etoposide.

Results

A recurrent homozygous nonsense variant in APTX gene (c.837G>A, p.W279*) was revealed in all affected individuals. qRT-PCR showed normal APTX levels in peripheral blood and lower levels in fibroblast cells. However, western blot showed the absence of APTX protein in patients’ skin fibroblasts. Significant hypersensitivity to H₂O₂, MMC and etoposide and lack of sensitivity to MMS were noted.

Conclusions

This is the first study to report the identification of a nonsense variant in the APTX gene (c.837G>A; p.W279*) in AOA1 patients within the Jordanian population. This study confirmed the need of WES to assist in the diagnosis of cerebellar ataxia and it emphasizes the importance of studying the pathophysiology of the APTX gene.

Clinical, Biomarker, and Molecular Delineations and Genotype-Phenotype Correlations of Ataxia With Oculomotor Apraxia Type 1

Importance

Ataxia with oculomotor apraxia type 1 (AOA1) is an autosomal recessive cerebellar ataxia due to mutations in the aprataxin gene (APTX) that is characterized by early-onset cerebellar ataxia, oculomotor apraxia, axonal motor neuropathy, and eventual decrease of albumin serum levels.

Objectives

To improve the clinical, biomarker, and molecular delineation of AOA1 and provide genotype-phenotype correlations.

Design, Setting, and Participants

This retrospective analysis included the clinical, biological (especially regarding biomarkers of the disease), electrophysiologic, imaging, and molecular data of all patients consecutively diagnosed with AOA1 in a single genetics laboratory from January 1, 2002, through December 31, 2014. Data were analyzed from January 1, 2015, through January 31, 2016.

Main Outcomes and Measures

The clinical, biological, and molecular spectrum of AOA1 and genotype-phenotype correlations.

Results

The diagnosis of AOA1 was confirmed in 80 patients (46 men [58%] and 34 women [42%]; mean [SD] age at onset, 7.7 [7.4] years) from 51 families, including 57 new (with 8 new mutations) and 23 previously described patients. Elevated levels of α-fetoprotein (AFP) were found in 33 patients (41%); hypoalbuminemia, in 50 (63%). Median AFP level was higher in patients with AOA1 (6.0 ng/mL; range, 1.1-17.0 ng/mL) than in patients without ataxia (3.4 ng/mL; range, 0.8-17.2 ng/mL; P < .01). Decreased albumin levels (ρ = -0.532) and elevated AFP levels (ρ = 0.637) were correlated with disease duration. The p.Trp279* mutation, initially reported as restricted to the Portuguese founder haplotype, was discovered in 53 patients with AOA1 (66%) with broad white racial origins. Oculomotor apraxia was found in 49 patients (61%); polyneuropathy, in 74 (93%); and cerebellar atrophy, in 78 (98%). Oculomotor apraxia correlated with the severity of ataxia and mutation type, being more frequent with deletion or truncating mutations (83%) than with presence of at least 1 missense variant (17%; P < .01). Mean (SD) age at onset was higher for patients with at least 1 missense mutation (17.7 [11.4] vs 5.2 [2.6] years; P < .001).

Conclusions and Relevance

The AFP level, slightly elevated in a substantial fraction of patients, may constitute a new biomarker for AOA1. Oculomotor apraxia may be an optional finding in AOA1 and correlates with more severe disease. The p.Trp279* mutation is the most frequent APTX mutation in the white population. APTX missense mutations may be associated with a milder phenotype.

Hypoalbuminemia in early onset dentatorubral-pallidoluysian atrophy due to leakage of albumin in multiple organs

We delineate a complication of hypoalbuminemia in dentatorubral-pallidoluysian atrophy (DRPLA), which we have found to be common in this disorder. In addition, we explored the pathogenesis of this phenomenon through clinical and histological examinations. Clinical course and laboratory findings of nine patients with childhood-onset DRPLA (aged 6-49 years; CAG repeat length 62-93) were retrospectively reviewed. Autopsied specimens from three patients were examined by histopathological and immunohistochemical analyses. Eight DRPLA patients showed hypoalbuminemia <3.5 g/dl in the initial stages of the disease (age, 2-32 years), which correlated with the CAG repeat length in each patient. Disease worsened in six patients, often triggered by febrile infections and accompanied by increased urinary protein excretion. One patient showed increased fecal α1-antitripsin while another showed accumulation of radioactive albumin in the urinary and gastrointestinal tracts after intravenous infusion. Immunohistochemistry revealed albumin-containing monocytes and astrocytes in the perivascular areas of the cerebral white matter. Fluid collection in the glomerular capillaries was noted. Immunolabeling using antibodies against the expanded polyglutamine (polyQ) polypeptide was positive in cerebral cortical neurons, hepatocytes, renal collecting ducts, and glomerular podocytes, which act as filtration barrier against serum proteins. Serum albumin appears to easily leak from blood vessels in certain visceral organs in DRPLA during later stages of the illness, particularly in the kidneys of patients with largely expanded CAG repeats. We hypothesize that the accumulation of the DRPLA gene product with expanded polyQ sequences in the podocytes results in the dysfunction of the glomerular filtration barrier.

Ataxia with oculomotor apraxia type1 (AOA1): novel and recurrent aprataxin mutations, coenzyme Q10 analyses, and clinical findings in Italian patients

Ataxia with oculomotor apraxia type1 (AOA1, MIM 208920) is a rare autosomal recessive disease caused by mutations in the APTX gene. We screened a cohort of 204 patients with cerebellar ataxia and 52 patients with early-onset isolated chorea. APTX gene mutations were found in 13 ataxic patients (6%). Eleven patients were homozygous for the known p.W279X, p.W279R, and p.P206L mutations. Three novel APTX mutations were identified: c.477delC (p.I159fsX171), c.C541T (p.Q181X), and c.C916T (p.R306X). Expression of mutated proteins in lymphocytes from these patients was greatly decreased. No mutations were identified in subjects with isolated chorea. Two heterozygous APTX sequence variants (p.L248M and p.D185E) were found in six families with ataxic phenotype. Analyses of coenzyme Q10 in muscle, fibroblasts, and plasma demonstrated normal levels of coenzyme in five of six mutated subjects. The clinical phenotype was homogeneous, irrespectively of the type and location of the APTX mutation, and it was mainly characterized by early-onset cerebellar signs, sensory neuropathy, cognitive decline, and oculomotor deficits. Three cases had slightly raised alpha-fetoprotein. Our survey describes one of the largest series of AOA1 patients and contributes in defining clinical, molecular, and biochemical characteristics of this rare hereditary neurological condition.

Early-onset ataxia with ocular motor apraxia and hypoalbuminemia/ataxia with oculomotor apraxia 1

DNA single-strand breaks (SSBs) are non-overlapping discontinuities in strands ofa DNA duplex. Significant attention has been given on the DNA SSB repair (SSBR) system in neurons, because the impairment of the SSBR causes human neurodegenerative disorders, including early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH), also known as ataxia-oculomotor apraxia Type 1 (AOA1). EAOH/AOA1 is characterized by early-onset slowly progressive ataxia, ocular motor apraxia, peripheral neuropathy and hypoalbuminemia. Neuropathological examination reveals severe loss of Purkinje cells and moderate neuronal loss in the anterior horn and dorsal root ganglia. EAOH/AOA1 is caused by the mutation in the APTX gene encoding the aprataxin (APTX) protein. APTX interacts with X-ray repair cross-complementing group 1 protein, which is a scaffold protein in SSBR. In addition, APTX-defective cells show increased sensitivity to genotoxic agents, which result in SSBs. These results indicate an important role ofAPTX in SSBR. SSBs are usually accompanied by modified or damaged 5'- and 3'-ends at the break site. Because these modified or damaged ends are not suitable for DNA ligation, they need to be restored to conventional ends prior to subsequent repair processes. APTX restores the 5'-adenylate monophosphate, 3'-phosphates and 3'-phosphoglycolate ends. The loss of function of APTX results in the accumulation of SSBs, consequently leading to neuronal cell dysfunction and death.

A novel mutation of aprataxin associated with ataxia ocular apraxia type 1: Phenotypical and genotypical characterization

Ataxia oculomotor apraxia type 1 (AOA1) is the most common form of autosomal recessive ataxia in Japan, and the second in Portugal after Friedreich ataxia. AOA1 is typically characterized by early-onset cerebellar ataxia, oculomotor apraxia, hypoalbuminemia, hypercholesterolemia and late axonal sensori-motor neuropathy. AOA1 is associated with the aprataxin gene (APTX) encoding a protein involved in DNA repair. We characterized a novel homozygous missense mutation of APTX in a 34 year-old female patient born from consanguineous parents. The mutation, a Val230Gly caused by a c.689 T>G substitution, involved the histidine-triad (HIT) domain of the protein, affected a phylogenetically conserved amino acid and was absent in the control population. We described the clinical and neurophysiological features, the findings at structural and functional brain imaging, and the pathological picture of the sural nerve biopsy. The report emphasized the genetical and phenotypical heterogeneity of AOA1 by demonstrating atypical features such as absence of oculomotor apraxia and signs of pyramidal involvement. Expression studies by Western blotting on fibroblasts demonstrated that the homozygous Val230Gly mutation was associated with decreased levels of APTX indicating a loss-of-function mechanism.

Aprataxin, causative gene product for EAOH/AOA1, repairs DNA single-strand breaks with damaged 3'-phosphate and 3'-phosphoglycolate ends

Aprataxin is the causative gene product for early-onset ataxia with ocular motor apraxia and hypoalbuminemia/ataxia with oculomotor apraxia type 1 (EAOH/AOA1), the clinical symptoms of which are predominantly neurological. Although aprataxin has been suggested to be related to DNA single-strand break repair (SSBR), the physiological function of aprataxin remains to be elucidated. DNA single-strand breaks (SSBs) continually produced by endogenous reactive oxygen species or exogenous genotoxic agents, typically possess damaged 3′-ends including 3′-phosphate, 3′-phosphoglycolate, or 3′-α, β-unsaturated aldehyde ends. These damaged 3′-ends should be restored to 3′-hydroxyl ends for subsequent repair processes. Here we demonstrate by in vitro assay that recombinant human aprataxin specifically removes 3′-phosphoglycolate and 3′-phosphate ends at DNA 3′-ends, but not 3′-α, β-unsaturated aldehyde ends, and can act with DNA polymerase β and DNA ligase III to repair SSBs with these damaged 3′-ends. Furthermore, disease-associated mutant forms of aprataxin lack this removal activity. The findings indicate that aprataxin has an important role in SSBR, that is, it removes blocking molecules from 3′-ends, and that the accumulation of unrepaired SSBs with damaged 3′-ends underlies the pathogenesis of EAOH/AOA1. The findings will provide new insight into the mechanism underlying degeneration and DNA repair in neurons.

A Japanese family with early-onset ataxia with motor and sensory neuropathy

We report the case of a Japanese family with hereditary ataxia with peripheral neuropathy. Three affected siblings from this family exhibited very similar clinical features: teenage-onset, slowly progressive ataxia, followed by distal weakness, which developed after the age of 30 years. Magnetic resonance imaging studies showed marked atrophy in the cerebellar hemisphere and vermis, and a sural nerve biopsy revealed a marked reduction in the number of both myelinated and unmyelinated fibers. All patients exhibited hyperglutamatemia, but serum levels of albumin and lipid were normal. The clinicopathological and biochemical features of these cases suggest that they form a distinct entity of autosomal recessive hereditary ataxia with peripheral neuropathy.

Spinocerebellar ataxia with ocular motor apraxia and DNA repair

At least four disorders, ataxia telangiectasia (AT), an ataxia-telangiectasia-like disorder, early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH)/ ataxia with oculomotor apraxia type 1 (AOA1), and ataxia with oculomotor apraxia type 2, are accompanied by ocular motor apraxia (OMA), which is an impairment of saccadic eye movement initiation. The characteristic pathological findings of EAOH/AOA1 and AT are a severe loss of Purkinje cells, severe myelin pallor of the posterior columns, and moderate neuronal loss in the dorsal root ganglia and anterior horn. Purkinje cells stimulate the fastigial nucleus and suppress omnipause neurons to initiate saccadic eye movement. The selective loss of Purkinje cells might cause OMA and disturb the cancellation of the vestibulo-ocular reflex. These disorders have the following common clinical features: ataxia, involuntary movements, and peripheral neuronopathy. In addition, the causative genes for these disorders are associated with the DNA/RNA quality control system. The impairment of DNA/ RNA integrity results in selective neuronal loss in these recessive-inherited ataxias.

Les ataxies cérébelleuses autosomiques récessives avec apraxie oculomotrice

INTRODUCTION

Autosomal recessive cerebellar ataxias (ARCA) comprise a phenotypically and genetically heterogeneous group of diseases. Recently, a subgroup of ARCA associated with oculomotor apraxia has been delineated.

STATE OF THE ART

The ataxias with oculomotor apraxia (AOA) include four distinct genetic entities at least: ataxia-telangiectasia, ataxia telangiectasia-like disorder, ataxia with oculomotor apraxia type 1 (AOA1) and type 2 (AOA2). The responsible genes, ATM, MRE11, APTX and SETX respectively, are implicated in DNA-break repair mechanisms.

CONCLUSION

We describe the phenotypic and genetic characteristics of these ataxias, based on a review of the literature and a personal study of AOA1 and AOA2 patients.

New autosomal recessive cerebellar ataxias with oculomotor apraxia

Autosomal recessive cerebellar ataxias (ARCAs) are a phenotypically and genetically heterogeneous group of diseases. Recently, a subgroup of ARCA associated with oculomotor apraxia (AOA) has been delineated. It includes at least four distinct genetic entities: ataxia-telangiectasia, ataxia-telangiectasia-like disorder, and ataxia with oculomotor apraxia type 1 (AOA1) and type 2 (AOA2). The phenotypes share several similarities, and the responsible genes, ATM, MRE11, APTX, and SETX, respectively, are all implicated in DNA break repair. As in many other DNA repair deficiencies, neurodegeneration is a hallmark of these diseases. Recently, the genes for two new autosomal recessive cerebellar ataxias with oculomotor apraxia, AOA1 and AOA2, were identified. Here, we report the phenotypic characteristics, genetic characteristics, and the recent advances concerning AOA1 and AOA2.

Early-onset ataxia with oculomotor apraxia with a novel APTX mutation

Early-onset ataxia with oculomotor apraxia and hypoalbuminemia is an autosomal recessive cerebellar ataxia characterized by oculomotor apraxia, peripheral neuropathy, and hypoalbuminemia. Mutations in aprataxin gene located at chromosome 9q13 have been identified recently in Japanese and European patients. This study reports two cases of siblings with early-onset ataxia with oculomotor apraxia and hypoalbuminemia, which manifested early onset before 2 years of age with relatively rapid progression and severe dystonia. Both of the siblings were compound heterozygotes with aprataxin gene mutations, 689 insT and G692A, in exon 5 that encodes the histidine triad domain of the aprataxin protein. The novel missense mutation, G692A, was not present in 40 unrelated and unaffected individuals.

The FHA domain of aprataxin interacts with the C-terminal region of XRCC1

Aprataxin (APTX) is the causative gene product for early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH/AOA1). In our previous study, we found that APTX interacts with X-ray repair cross-complementing group 1 (XRCC1), a scaffold protein with an essential role in single-strand DNA break repair (SSBR). To further characterize the functions of APTX, we determined the domains of APTX and XRCC1 required for the interaction. We demonstrated that the 20 N-terminal amino acids of the FHA domain of APTX are important for its interaction with the C-terminal region (residues 492-574) of XRCC1. Moreover, we found that poly (ADP-ribose) polymerase-1 (PARP-1) is also co-immunoprecipitated with APTX. These findings suggest that APTX, together with XRCC1 and PARP-1, plays an essential role in SSBR.

Characterization of ataxias with magnetic resonance imaging and spectroscopy

A wide variety of autosomal transmitted ataxias exist and their ultimate characterization requires genetic testing. Common clinical characteristics among different ataxia types complicate the choice of the appropriate genetic test. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) generally show cerebellar or cerebral atrophy and perturbed metabolite levels which differ between ataxias. In order to help the clinician accurately identify the ataxia type, reported MRI and MRS data in different brain regions are summarized for more than 60 different types of autosomal inherited and sporadic ataxias.

Aprataxin, the causative protein for EAOH is a nuclear protein with a potential role as a DNA repair protein

Early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH) is an autosomal recessive neurodegenerative disorder characterized by early-onset ataxia, ocular motor apraxia, and hypoalbuminemia. Recently, the causative gene for EAOH, APTX, has been identified. Of the two splicing variants of APTX mRNA, the short and the long forms, long-form APTX mRNA was found to be the major isoform. Aprataxin is mainly located in the nucleus, and, furthermore, the first nuclear localization signal located near the amino terminus of the long-form aprataxin is essential for its nuclear localization. We found, based on the yeast two-hybrid and coimmunoprecipitation experiments, that the long-form but not the short-form aprataxin interacts with XRCC1 (x-ray repair cross-complementing group 1). Interestingly the amino terminus of the long-form aprataxin is homologous with polynucleotidekinase-3'-phosphatase, which has been demonstrated to be involved in base excision repair, a subtype of single-strand DNA break repair, through interaction with XRCC1, DNA polymerase beta, and DNA ligase III. These results strongly support the possibility that aprataxin and XRCC1 constitute a multiprotein complex and are involved in single-strand DNA break repair, and furthermore, that accumulation of unrepaired damaged DNA underlies the pathophysiological mechanisms of EAOH.

Severe generalized dystonia as a presentation of a patient withaprataxin gene mutation

A 14-year-old girl, homozygous for an insertion mutation of aprataxin (APTX), 689 ins T, is described. She presented with severe generalized dystonia, ataxia, ocular motor apraxia, and areflexia. The dystonia of this patient suggests involvement of the basal ganglia or thalamus, along with clinical diversity in this disorder.

The gene mutated in ataxia-ocular apraxia 1 encodes the new HIT/Zn-finger protein aprataxin

The newly recognized ataxia-ocular apraxia 1 (AOA1; MIM 208920) is the most frequent cause of autosomal recessive ataxia in Japan and is second only to Friedreich ataxia in Portugal. It shares several neurological features with ataxia-telangiectasia, including early onset ataxia, oculomotor apraxia and cerebellar atrophy, but does not share its extraneurological features (immune deficiency, chromosomal instability and hypersensitivity to X-rays). AOA1 is also characterized by axonal motor neuropathy and the later decrease of serum albumin levels and elevation of total cholesterol. We have identified the gene causing AOA1 and the major Portuguese and Japanese mutations. This gene encodes a new, ubiquitously expressed protein that we named aprataxin. This protein is composed of three domains that share distant homology with the amino-terminal domain of polynucleotide kinase 3'- phosphatase (PNKP), with histidine-triad (HIT) proteins and with DNA-binding C2H2 zinc-finger proteins, respectively. PNKP is involved in DNA single-strand break repair (SSBR) following exposure to ionizing radiation and reactive oxygen species. Fragile-HIT proteins (FHIT) cleave diadenosine tetraphosphate, which is potentially produced during activation of the SSBR complex. The results suggest that aprataxin is a nuclear protein with a role in DNA repair reminiscent of the function of the protein defective in ataxia-telangiectasia, but that would cause a phenotype restricted to neurological signs when mutant.

Early-onset ataxia with ocular motor apraxia and hypoalbuminemia is caused by mutations in a new HIT superfamily gene

Friedreich ataxia (FRDA), the most common autosomal recessive neurodegenerative disease among Europeans and people of European descent, is characterized by an early onset (usually before the age of 25), progressive ataxia, sensory loss, absence of tendon reflexes and pyramidal weakness of the legs. We have recently identified a unique group of patients whose clinical presentations are characterized by autosomal recessive inheritance, early age of onset, FRDA-like clinical presentations and hypoalbuminemia. Linkage to the FRDA locus, however, was excluded. Given the similarities of the clinical presentations to those of the recently described ataxia with oculomotor apraxia (AOA) linked to chromosome 9p13, we confirmed that the disorder of our patients is also linked to the same locus. We narrowed the candidate region and have identified a new gene encoding a member of the histidine triad (HIT) superfamily as the 'causative' gene. We have called its product aprataxin; the gene symbol is APTX. Although many HIT proteins have been identified, aprataxin is the first to be linked to a distinct phenotype.

A novel member of the Ig superfamily, turtle, is a CNS-specific protein required for coordinated motor control

We describe here the cloning and functional characterization of a neural-specific novel member of the Ig superfamily, turtle (tutl), with a structure of five Ig C2-type domains, two fibronectin type III domains, and one transmembrane region. Alternative splicing of the tutl gene produces at least four Tutl isoforms, including two transmembrane proteins and two secreted proteins, with primary structures closely related to a human brain protein (KIAA1355), the Deleted in Colorectal Cancer/Neogenin/Frazzled receptor family, and the Roundabout/Dutt1 receptor family. An allelic series of tutl gene mutations resulted in recessive lethality to semilethality, indicating that the gene is essential. In contrast to other family members, tutl does not play a detectable role in axon pathfinding or nervous system morphogenesis. Likewise, basal synaptic transmission and locomotory movement are unaffected. However, tutl mutations cause striking movement defects exhibited in specific types of highly coordinated behavior. Specifically, tutl mutants display an abnormal response to tactile stimulation, the inability to regain an upright position from an inverted position (hence, "turtle"), and the inability to fly in adulthood. These phenotypes demonstrate that tutl plays an essential role in establishing a nervous system capable of executing coordinated motor output in complex behaviors.

Homozygosity mapping of Portuguese and Japanese forms of ataxia-oculomotor apraxia to 9p13, and evidence for genetic heterogeneity

Ataxia with oculomotor apraxia (AOA) is characterized by early-onset cerebellar ataxia, ocular apraxia, early areflexia, late peripheral neuropathy, slow progression, severe motor handicap, and absence of both telangiectasias and immunodeficiency. We studied 13 Portuguese families with AOA and found that the two largest families show linkage to 9p, with LOD scores of 4.13 and 3.82, respectively, at a recombination fraction of 0. These and three smaller families, all from northern Portugal, showed homozygosity and haplotype sharing over a 2-cM region on 9p13, demonstrating the existence of both a founding event and linkage to this locus, AOA1, in the five families. Three other families were excluded from this locus, demonstrating nonallelic heterogeneity in AOA. Early-onset cerebellar ataxia with hypoalbuminemia (EOCA-HA), so far described only in Japan, is characterized by marked cerebellar atrophy, peripheral neuropathy, mental retardation, and, occasionally, oculomotor apraxia. Two unrelated Japanese families with EOCA-HA were analyzed and appeared to show linkage to the AOA1 locus. Subsequently, hypoalbuminemia was found in all five Portuguese patients with AOA1 with a long disease duration, suggesting that AOA1 and EOCA-HA correspond to the same entity that accounts for a significant proportion of all recessive ataxias. The narrow localization of AOA1 should prompt the identification of the defective gene.

Early onset cerebellar ataxia with retained tendon reflexes: foot deformity in a first grade family member

Early onset cerebellar ataxia with retained tendon reflexes (EOCA) is a clinical syndrome characterised by progressive cerebellar ataxia with an onset before the age of 25 years and a wide spectrum of associated features. It is distinguished from Friedreich's ataxia (FA) mainly by the preservation of tendon reflexes, a better prognosis, and the absence of GAA expansion in the frataxin gene. Although EOCA is thought to be a hereditary disorder with an autosomal recessive mode of inheritance, genetic heterogeneity might underlie the spectrum of clinical features. In this case report we describe a patient with EOCA accompanied by pes cavus, hammer toes and peripheral neuropathy. The patient's father did not have any ataxia, but had the same foot deformities as his daughter and a slight peripheral neuropathy. The possible relationship between these clinical features is discussed.

Hereditary motor and sensory neuropathy associated with cerebellar atrophy (HMSNCA): clinical and neuropathological features of a Japanese family

We report clinicopathological features of a Japanese family with hereditary motor and sensory neuropathy associated with cerebellar atrophy (HMSNCA). Four affected members from a single generation were examined. They shared common clinical features, including insidious onset in teenage, slowly progressive cerebellar ataxia, amyotrophy, sensory disturbance, and dementia. In addition, all the patients showed hypoalbuminemia and hyperlipidemia and a marked atrophy of the cerebellum on magnetic resonance images. Autopsy of the proband revealed a severe loss of Purkinje cells, degeneration of posterior columns and spinocerebellar tracts of the spinal cord, and a marked loss of myelinated and unmyelinated fibers in the peripheral nerves. We consider that HMSNCA is a distinct form of hereditary multisystem neuronal degeneration.

Familial spastic paraplegia, axonal sensory-motor polyneuropathy and bulbar amyotrophy with facial dysmorphia: new cases of Troyer-like syndrome

We studied two Libyan siblings, born to healthy consanguineous parents, who had suffered from a progressive neurological disorder, characterized by facial dysmorphia, ataxia, spastic paraplegia and an axonal sensory-motor polyneuropathy, since the age of 3 years. The clinical picture progressed slowly over a 6-year period to involve also bulbar and distal limb muscles. Interestingly, we found unusual tubulofilamentous inclusions in peripheral nerves and presynaptic buttons at the neuromuscular junctions. Describing the clinical picture of this presumably new disorder, we comment on the difference from similar conditions.