[Validation of the Spanish version of the Charcot-Marie-Tooth disease Pediatric Scale (CMTPedS)]

INTRODUCTION AND AIMS

The Charcot-Marie-Tooth Pediatric Scale (CMTPedS) is a validated and change-sensitive tool for assessing the severity of neuropathy in children and adolescents between 3 and 20 years of age. The aim of this article is to translate and validate a Spanish version of the CMTPedS in order to disseminate its use in Spanish-speaking countries.

MATERIALS AND METHODS

The process used to translate the CMTPedS into Spanish was the reverse parallel translation method based on the principles of good practice for translation and the cultural adaptation process of the Food and Drug Administration Guidelines. A direct translation of the original source of the CMTPedS into Spanish was performed first and reviewed by experts in Charcot-Marie-Tooth (CMT) disease trained in the use of the CMTPedS tool. The Spanish version was then translated back into English by a linguist specialised in translation.

RESULTS

The preliminary Spanish version of the CMTPedS was evaluated in 18 children with CMT aged 6-20 years (mean: 13.27). The scale was well tolerated and easy for children to understand and easy for clinicians to apply. None of the patients had any difficulty completing the scale.

CONCLUSIONS

The Spanish version of the CMTPedS can be used for monitoring and conducting clinical trials in the Spanish population and in Spanish-speaking countries.

Bi-allelic mutations in EGR2 cause autosomal recessive demyelinating neuropathy by disrupting the EGR2-NAB complex

BACKGROUND AND PURPOSE

Mutations in the early growth response 2 gene (EGR2) cause demyelinating, but also axonal, neuropathies differing in severity and age of onset. Except for one family, all reported cases have autosomal dominant inheritance and mutations are localized within the three zinc finger (ZNF) DNA-binding domain. The aim of this study was to provide a clinical and molecular analysis of a novel recessive mutation in EGR2.

METHODS

Clinical and electrophysiological assessments of three affected patients, from a consanguineous family, were performed. Genetic analyses of EGR2 were carried out by Sanger sequencing. Functional effects of clinical recessive mutations were assessed using a mammalian two-hybrid assay.

RESULTS

A novel missense mutation (c.791C>T; p.P264L) in the homozygous state was detected outside the ZNF domains of the EGR2 gene. Three affected siblings presented with distal demyelinating polyneuropathy with severe sensory loss, progressive thoracolumbar scoliosis and trigeminal neuralgia. Respiratory compromise and cranial nerve dysfunction were also found. Our data indicate that the p.P264L mutation prevents interaction of EGR2 transcription factor with NAB corepressors, suggesting that a disruption of the NAB-EGR2 protein interactions can result in dramatic neuropathy.

CONCLUSION

Mutations in, or next to, the R1 domain of EGR2 should be considered with extreme caution for genetic counseling, since these could cause a severe neuropathy with an autosomal recessive manner of transmission.

New insights into the pathophysiology of fasciculations in amyotrophic lateral sclerosis: An ultrasound study

OBJECTIVE

To describe the fasciculation pattern in ALS and to analyse its clinical and pathophysiological significance.

METHODS

Ultrasound of 19 muscles was performed in 44 patients with a recent diagnosis (<90 days) of ALS. The number of fasciculations was recorded in each muscle and the muscle thickness and strength were additionally measured in limb muscles. A subgroup of patients were electromyographically assessed.

RESULTS

US was performed in 835 muscles and EMG was available in 263 muscles. US detected fasciculations more frequently than EMG. Fasciculations were widespread, especially in upper limbs onset patients and in the cervical region. Fasciculations' number inversely associated with ALSFR-R and body mass index (BMI) and directly with BMI loss and upper motor neuron (UMN) impairment. Our statistical model suggest that fasciculations increase with the initial lower motor neuron (LMN) degeneration, reach their peak when the muscle became mildly to moderately weak, decreasing afterwards with increasing muscle weakness and atrophy.

CONCLUSIONS

Our study suggests that both UMN and LMN degeneration trigger fasciculations causing BMI loss. The degree of LMN impairment could account for differences in fasciculations' rates within and between muscles.

SIGNIFICANCE

In ALS, fasciculations could explain the link between hyperexcitability and BMI loss.

Genetics of the Charcot-Marie-Tooth disease in the Spanish Gypsy population: the hereditary motor and sensory neuropathy-Russe in depth

Four private mutations responsible for three forms demyelinating of Charcot-Marie-Tooth (CMT) or hereditary motor and sensory neuropathy (HMSN) have been associated with the Gypsy population: the NDRG1 p.R148X in CMT type 4D (CMT4D/HMSN-Lom); p.C737_P738delinsX and p.R1109X mutations in the SH3TC2 gene (CMT4C); and a G>C change in a novel alternative untranslated exon in the HK1 gene causative of CMT4G (CMT4G/HMSN-Russe). Here we address the findings of a genetic study of 29 Gypsy Spanish families with autosomal recessive demyelinating CMT. The most frequent form is CMT4C (57.14%), followed by HMSN-Russe (25%) and HMSN-Lom (17.86%). The relevant frequency of HMSN-Russe has allowed us to investigate in depth the genetics and the associated clinical symptoms of this CMT form. HMSN-Russe probands share the same haplotype confirming that the HK1 g.9712G>C is a founder mutation, which arrived in Spain around the end of the 18th century. The clinical picture of HMSN-Russe is a progressive CMT disorder leading to severe weakness of the lower limbs and prominent distal sensory loss. Motor nerve conduction velocity was in the demyelinating or intermediate range.

Autoimmunity as a prognostic factor in sporadic adult onset cerebellar ataxia

Cerebellar adult onset ataxia is a heterogeneous condition. The aim of this study was to ascertain if there is a heightened autoimmune background in patients with sporadic cerebellar ataxia of unknown origin, and if autoimmunity correlates with a more rapid evolution of the ataxia. We selected patients with sporadic progressive adult onset cerebellar ataxia with a follow-up of >5 years. As controls we included 43 patients with genetically demonstrated hereditary ataxia. All patients were tested for a panel of neuronal (onconeuronal, glutamate-decarboxylase [GAD], IgG/IgA transglutaminase 6 antibodies) and systemic non-neuronal antibodies (including IgG/IgA gliadin and transglutaminase 2, thyroperoxidase, thyroglobulin, antinuclear, striational, smooth muscle, mitochondrial, liver kidney microsomal, and parietal gastric cells antibodies). Correlation between the antibodies and disease progression was studied with Cox regression models and Kaplan-Meier plots. Forty-four patients were included. All patients were negative for onconeuronal or GAD antibodies. There were no significant differences between patients and controls in the prevalence of transglutaminase 6, 2, gliadin, or thyroid antibodies. However, when we studied the panel of systemic non-neuronal autoantibodies as a group, antibodies were more frequent in patients with sporadic ataxia (p = 0.018). The presence of one or more systemic non-neuronal antibodies correlated with a faster evolution to stage 2 (loss of independent gait) (p = 0.03) and shorter survival (p = 0.03) in patients with sporadic ataxia. We conclude that there is probably a heightened autoimmune background in some patients with sporadic cerebellar ataxia of unknown origin. The presence of systemic non-neuronal autoantibodies is a prognostic marker.

[Guidelines for molecular diagnosis of Charcot-Marie-Tooth disease]

INTRODUCTION

Charcot-Marie-Tooth disease (CMT) is the most frequent form of inherited neuropathy. In accordance with the inheritance pattern and degree of slowing of motor conduction velocity (MCV) of the median nerve, CMT encompasses five main forms: CMT1 (autosomal dominant [AD] or X-linked transmission and MCV < 38 m/s); CMT2 (AD or X-linked transmission and MCV > 38 m/s); CMT4 (autosomal recessive [AR] and severe slowing of MCV); AR-CMT2 (AR transmission and MCV > 38 m/s); and DI-CMT (intermediate form with AD transmission and MCV between 30 and 40 m/s). In spite of its stereotyped semiological repertoire (basically, symptoms and signs of sensory-motor polyneuropathy and pes cavus), CMT seems to be one of the most complex hereditary neurodegenerative syndromes, 31 causative genes having been cloned.

DEVELOPMENT

This paper is aimed at performing a nosological review of the disease, emphasising the guidelines for its molecular diagnosis. Genetic epidemiological studies and genotypes reported in Spanish patients are revised.

CONCLUSIONS

In the great majority of CMT cases, mutations involve a reduced number of genes, namely: for CMT1, PMP22, GJB1 and MPZ; for CMT2, MFN2 and GJB1; for CMT4, GDAP1, and NDRG1, HK1 and SH3TC2 (gypsies); for AR-CMT2, GDAP1; and for DI-CMT, GJB1 and MPZ. Given their low prevalence, mutations in other pathogenic genes should be investigated after discarding the previous ones. There is no place for the indiscriminate use of diagnostic CMT genetic panels.

Peripheral nerve hyperexcitability: a clinical and immunologic study of 38 patients

OBJECTIVE

We studied a case series of peripheral nerve hyperexcitability (PNH) aiming to describe clinical characteristics, immunologic and cancer associations, antibodies against neuronal antigens (voltage-gated potassium channel antibodies [VGKC-Abs] and other), and muscle biopsy findings.

METHODS

Patients presenting with clinical and electrophysiologic signs of PNH were selected. We studied clinical and electrophysiologic features; a panel of non-neuronal organ-specific antibodies, immunofluorescence on rat nervous tissues, and radioimmunoprecipitation for VGKC-Abs; and muscle biopsies.

RESULTS

Thirty-eight patients were included. After the exclusion of 6 cases with axonopathy of known origin, patients were subdivided according to the presence of electrophysiologic findings of motor axonopathy and association with cancer: axonopathic-PNH (group A: 12 patients), isolated nonparaneoplastic PNH (group B: 16 patients), and isolated paraneoplastic PNH (3 with thymoma and myasthenia gravis, 1 with thyroid carcinoma). PNH clinical features were similar in groups A and B. We found an overall high prevalence of clinical autoimmunity (33% of group A and 63% of group B) and systemic non-neuronal autoantibodies (42% of group A and 75% of group B). However, VGKC-Abs were only positive in 2 patients of group B. Ten patients underwent muscle biopsy, which showed inflammatory changes in 2 cases and nonspecific myopathic features in 8.

CONCLUSIONS

PNH is a heterogeneous disorder involving the peripheral nerves in patients with a high propensity for developing autoimmunity. Associated muscle diseases are frequent in the form of myositis, myasthenia gravis, or nonspecific myopathic pathologic findings. VGKC-Abs were uncommon in this series.

MYH7 gene tail mutation causing myopathic profiles beyond Laing distal myopathy

OBJECTIVE

To describe a wide range of clinical and pathologic myopathic profiles associated with the p.K1729del mutation in the MYH7 gene, known to cause Laing distal myopathy.

METHODS

A study conducted in the Safor region (Spain), setting of a large cluster of patients. Clinical, neurophysiologic, muscle imaging, and muscle biopsy studies and MYH7 gene sequencing were investigated in 32 patients from 4 kindreds. Data from 36 deceased or nonexamined patients were collected from hospital records or relatives.

RESULTS

Onset ranged from congenital to the 6th decade. All patients presented weakness of great toe/ankle dorsiflexors and many had associated neck flexor, finger extensor, and mild facial weakness. In most cases, involvement of proximal and axial muscles was observed either clinically or by muscle imaging, sometimes giving rise to scapuloperoneal and limb-girdle syndromes. Disabling myalgias, skeletal deformities, and dilated cardiomyopathy in one patient were associated features. Life expectancy was not reduced but the spectrum of disability ranged from asymptomatic to wheelchair confined. Electromyographic neurogenic features were frequently recorded. Muscle fiber type disproportion, core/minicore lesions, and mitochondrial abnormalities were the most relevant pathologic alterations. All patients carried the p.K1729del mutation in MYH7.

CONCLUSIONS

The p.K1729del mutation in the MYH7 gene expresses notable clinical variability and electromyographic and pathologic features that can lead to the misdiagnosis of neurogenic atrophies, congenital myopathies, or mitochondrial myopathies. Mutations in genes encoding other sarcomeric and reticulo-sarcoplasmic proteins involved in calcium regulation share pathologic characteristics with our patients, suggesting a possible pathogenetic connection.

[Migraine with aura, right-to-left shunt and frequency of seizures]

INTRODUCTION

The high prevalence of patent foramen ovale in migraine with aura (MWA) seems to be well established; yet, the possible relation between the magnitude of the right-to-left shunt (RLS) and MWA is not so clear. As a hypothesis, if the RLS played a precipitating role, subjects with a larger degree of shunt might experience a higher number of seizures. We examine this possible relationship between the magnitude of the shunt and the incidence of seizures.

PATIENTS AND METHODS

We examined a series of 72 patients with MWA to obtain the frequencies of seizures (dividing them into three groups of increasing frequency), history and precipitating factors. The presence and magnitude of the RLS were later determined by means of transcranial Doppler ultrasonography, following a method that had previously been validated. Univariate analysis was then used to evaluate the possible association between the magnitude of the shunt and the frequency of seizures.

RESULTS

The mean age was 36 years. RLS appeared in 44 patients (61.1%) and followed a 'shower/curtain' pattern in 38% of cases. Frequency of seizures was low in 27%, medium in 45% and high in 27% of patients. Frequency was not associated with the magnitude of the shunt even when only high-frequency cases were considered. High frequency was associated, however, with certain precipitating factors.

CONCLUSIONS

Our study confirms the existence of a high prevalence of RLS in patients with MWA, but no association was found between the magnitude of the shunt and the frequency of the seizures. As discussed here, these findings are partly at odds with a 'threshold' type of association or mechanism that precipitates seizures.

The p.R1109X mutation in SH3TC2 gene is predominant in Spanish Gypsies with Charcot-Marie-Tooth disease type 4

Charcot-Marie-Tooth (CMT) disease type 4 (CMT4) is the name given to autosomal recessive forms of hereditary motor and sensory neuropathy (HMSN). When we began this study, three genes or loci associated with inherited peripheral neuropathies had already been identified in the European Gypsy population: HMSN-Lom (MIM 601455), HMSN-Russe (MIM 605285) and the congenital cataracts facial dysmorphism neuropathy syndrome (MIM 604168). We have carried out genetic analyses in a series of 20 Spanish Gypsy families diagnosed with a demyelinating CMT disease compatible with an autosomal recessive trait. We found the p.R148X mutation in the N-myc downstream-regulated gene 1 gene to be responsible for the HMSN-Lom in four families and also possible linkage to the HMSN-Russe locus in three others. We have also studied the CMT4C locus because of the clinical similarities and showed that in 10 families, the disease is caused by mutations located on the SH3 domain and tetratricopeptide repeats 2 (SH3TC2) gene: p.R1109X in 20 out of 21 chromosomes and p.C737_P738delinsX in only one chromosome. Moreover, the SH3TC2 p.R1109X mutation is associated with a conserved haplotype and, therefore, may be a private founder mutation for the Gypsy population. Estimation of the allelic age revealed that the SH3TC2 p.R1109X mutation may have arisen about 225 years ago, probably as the consequence of a bottleneck.

[Different phenotypes of Charcot-Marie-Tooth disease caused by mutations in the same gene. Are classical criteria for classification still valid?]

Molecular genetic research is leading to the continuous discovery of new genes and protein involved in peripheral nerves function. Simultaneously, extended clinical, neurophysiological and pathological research has yielded new genotype-phenotype correlation on Charcot-Marie-Tooth disease (CMT). This has made it possible to know that several genes can cause both demyelinating (CMT1) and axonal (CMT2) phenotypes. Those observations have questioned the validity of some current criteria for CMT classification and raise the need for new strategies for diagnosis. The discovery of Schwann cell-axon interaction is a challenge for coming years. In this review, we extensively analyzed mutations of genes that give rise to CMT1 or CMT2 phenotypes. There are at least three forms of genetic variability. MPZ gene mutations yield a real allelism, that is, CMT1 or CMT phenotypes associated to specific mutation by site or quality. GADP1 and probably NF-L gene manifest different phenotypes but only in terms of nerve conduction velocity (CV). Evidence is provided that indicates that CV reduction in GADP-1 neuropathy may be the result of axonal loss. Finally a third form of variability is present in CMTX due to the degree of clinical expression in females related with the inactivation of chromosome X.

[The genetics of type 1 Charcot-Marie-Tooth disease, the hereditary focal neuropathies and the hereditary distal motor neuropathies]

INTRODUCTION

Charcot-Marie-Tooth disease (CMTD) or hereditary motor and sensory neuropathy shows great genetic heterogeneity. The type 1 (CMT-1) or demyelinating form and the type 2 (CMT-2) or neuronal form are two clinically and genetically distinct forms.

DEVELOPMENT

Apart from the above mentioned motor and sensory forms, there is another type of neuropathy in which the clinical and neurophysiological involvement is exclusively motor and is known as distal spinal atrophy or hereditary distal motor neuropathy (HDMN), which is a syndrome to be included among the CMTD. The CMT-1 is the most prevalent form and the best understood from the genetic point of view. At least four genes have been reported to be involved: the gene for 22 kDa peripheral myelin protein (PMP-22), situated on the 17p11.2 chromosome (locus CMT-1A); the gene for myelin 0 protein situated on chromosome 1q23 (locus CMT-1B); the gene for conexine 32 (Cx32), found on chromosome Xq13 (locus CMT-X) and the gene EGR2 found on chromosome 10q21.1-q22.1. The genes PMP-22 and PO are related to autosomal dominant forms, the gene Cx32 is transmitted linked to chromosome X and transmission of gene EGR2 has been shown in both autosomal dominant and autosomal recessive forms. In the demyelinating forms with autosomal recessive inheritance, positive linkage has been found on four different loci: 8q21.1 (CMT-4A), 11q23 (CMT-4B), 5q23-33 (CMT-4C) and 8q24 in a form related to deafness (CMT-Lom). Two loci have been identified for the autosomal dominant forms of the HDMN. A large family initially and predominantly of the upper limbs is mapped on chromosome 7p (HDMN-V) and another with the classical phenotype mapped on chromosome 12q24. In the familial neuropathy with liability to pressure palsies in most families, deletion of the locus CMT-1A was found, and in rare cases mutation precisely of the PMP-22 gene. In familial amyotrophic neuralgia, genetic molecular analysis has shown linkage with markers on the chromosome 17q24-25.

Early onset cerebellar ataxia and preservation of tendon reflexes: clinical phenotypes associated with GAA trinucleotide repeat expanded and non-expanded genotypes

The aim of this study was to determine phenotypie characteristics of patients with early onset cerebellar ataxia (EOCA) with preserved tendon reflexes. The series comprises 25 patients, representing 10% of all ataxic patients who have been genetically studied in our laboratory since 1990. There were 11 males and 14 females. Fourteen patients were homozygous for the GAA expansion on chromosome 9q13 (group 1) and therefore a diagnosis of Friedreich's ataxia with retained reflexes (FARR) was given. The remaining 11 patients had two normal non-expanded alleles (group 2) and a working diagnosis of EOCA with retained reflexes (EOCARR) was established. Mean ages of onset were 13.7 +/- 5.9 years (3-25) for group 1 and 10.3 +/- 7.3 for group 2; the difference was not significant. Frequencies of symptoms and signs were also comparable for both groups the only significant differences being the higher frequency of nystagmus, cardiomyopathy and sensory neuropathy in group 1 patients. There was a tendency for FARR patients to have higher frequencies of hypopallesthesia in the lower limbs and skeletal deformities. In none of the cases diabetes mellitus was observed. We conclude that differentiation of FARR and EOCARR may be suspected by classical clinical and electrophysiological data and confirmed by analysis of the GAA repeat.

[A risk of developing multiple sclerosis following an outbreak of optic neuritis during a mean follow-up of 4.5 years]

OBJECTIVE

The current study was designed to determine the risk of developing clinically definite multiple sclerosis (CDMS) after an isolated idiopathic optic neuritis (ON).

PATIENTS AND METHODS

We retrospectively studied 28 patients (range from 18-45 years) who presented a unilateral acute ON between 1 st April and 31 st December. We excluded optic neuropathy of other causes, a previous diagnosis of MS or systemic diseases associated with ON. Patients underwent brain MRI, visual evoked potentials (VEPs), somatosensory evoked potentials (SEPs) and brainstem auditory evoked potentials (BAEPs). The mean interval between ON onset and MRI was 3.1 months. 24 patients were treated with corticosteroids in different ways: oral prednisone (14) and intravenous methylprednisolone (10). Mean duration of the follow-up was 4.5 years in 26 patients.

RESULTS

Brain MRI detected white matter areas with increased signal in 10 of 25 patients (40%). Eight (30%) had bilateral anormalities on VEP, while SEPs and BAEPs revealed anormalities in one patient (5.5%). Two out 26 patients (7.7%) developed CDMS; one was treated with oral prednisone and the other with intravenous corticosteroids. No patients with normal MRI developed MS compared to 20% of patients with lesions on initial brain MRI. The only patient with abnormal SEPs and BAEPs did not develop MS.

CONCLUSIONS

We found in our population low rate of developing CDMS with higher risk for those ON with abnormalities on initial brain MRI.

Mutational analysis of the MPZ, PMP22 and Cx32 genes in patients of Spanish ancestry with Charcot-Marie-Tooth disease and hereditary neuropathy with liability to pressure palsies

Charcot-Marie-Tooth disease (CMT) and hereditary neuropathy with liability to pressure palsies (HNPP) are two inherited peripheral neuropathies. The most prevalent mutations are a reciprocal 1.5-Mb duplication and 1.5-Mb deletion, respectively, at the CMT1A/HNPP locus on chromosome 17p11.2. Point mutations in the coding region of the myelin genes, peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ) or connexin 32 (Cx32) have been reported in CMT patients, including CMT type 1 (CMT1), CMT type 2 (CMT2) and Déjérine-Sottas neuropathy (DS) patients, and only in the coding region of PMP22 in HNPP families lacking a deletion. We have investigated point and small mutations in the MPZ, PMP22 and Cx32 genes in a series of patients of Spanish ancestry: 47 CMT patients without duplications, and 5 HNPP patients without deletions. We found 15 different mutations in 16 CMT patients (34%). Nine different mutations in ten patients were detected in the Cx32 gene, this being the most frequently involved gene in this series, whereas five mutations involved the MPZ gene and only one the PMP22 gene. Six out of nine nucleotide substitutions in the Cx32 gene involved two codons encoding arginine at positions 164 and 183, suggesting that these two codons may constitute two Cx32 regions prone to mutate in the Spanish population. Analysis of HNPP patients revealed a 5' splicing mutation in intron 1 of the PMP22 gene in a family with autosomal dominance, which confirms allelic heterogeneity in HNPP. Ectopic mRNA analysis on leukocytes suggests that this mutation might behave as a null allele.

[Distal spinal muscular atrophy]

Chronic spinal muscular atrophy usually presents in childhood or adolescence, generally as predominant proximal muscle weakness. Other less common forms involving distal muscles can be either partial or generalized and their prognosis is relatively good. At least three well-defined types can be identified: a) a form located in the upper extremities that typically affects young men, is not familial and is highly prevalent in Asia; b) a more generalized form that can be either familial or isolated and that resembles Charcot-Marie-Tooth disease in the distribution of muscle weakness and prognosis, and c) another generalized form that starts in and mainly involves the upper extremities, is inherited in an autosomal dominant manner and is accompanied by laryngeal involvement. We review the literature and describe 27 patients with distal spinal muscular atrophy resembling Charcot-Marie-Tooth disease.

[Genetics of peripheral neuropathies and hereditary ataxias]

Charcot-Marie-Tooth disease (CMT) is a hereditary motor-sensory neuropathy with a large genetic heterogeneity. Type 1 (CMT1), or demyelinating CMT, and type 2 (CMT2), or neuronal CMT, are two genetically and clinically distinct entities. CMT1 is the more prevalent and better understood of the two from a genetic standpoint. At least three genes have been shown to be implicated: the 22Kda (PMP22) gene for peripheral myelin protein located in the 17p11.2 chromosome (the CMT1A locus), the P0 myelin protein gene located in the 1q23 chromosome (the CMT1B locus), and the connexin 32 (Cx32) gene located in the Xq13 chromosome (CMTX locus). The most common mutation in CMT1, found in 70% of cases, is a tandem duplication of 1,500 kb at the CMT1A locus. Point mutations have also been described in the PMP22 gene and in P0 and Cx32. Déjerine-Sortas syndrome (DSS) is caused by point mutations in PMP22 and P0 genes, whereas familial neuropathy with liability to pressure palsies (FNPP) or tomacular neuropathy are caused mainly by deletion of 1,500 kb at the CMT1A locus, although point mutations have also been described in the PMP22 gene. Altogether, we can say that CMT1, DSS and FNPP are different clinical expressions of the same genetic pathology and reflect a phenotypic spectrum of related myelin disorders. Hereditary ataxias constitute a wide ranging and heterogeneous set of clinical entities with different ages of onset, patterns of system involvement and type of inheritance. The most common form is Friedreich's ataxia, a autosomally recessive inherited disease whose gene is located in the 9q13 chromosome, though it has not yet been isolated. This disease has various clinical presentations, which does not imply genetic heterogeneity. Dominant autosomal cerebellar ataxias, on the other hand, are extremely heterogeneous. Seven genetic loci have been described, some of which are associated to cerebellar plus forms and expanded unstable triplet sequences of CAG in SCA1 and SCA3/MJD. One locus has been described for the "pure cerebellar form" (ACAD type III) (locus SCA5) and another for the form with retinopathy (ACAD type II) (locus SCA7).

[Deletion of 17p11.2 chromosome in Spanish families with hereditary neuropathy and abnormal sensitivity to pressure]

Hereditary neuropathy with abnormal liability to pressure palsies (HNPP) is a dominant autosomally transmitted disease that gives rise to foci of peripheral nerve myelination, reducing conduction and leading to episodes of palsy and sensory changes that are all linked to sensitivity to pressure and traction on the affected nerve roots. The molecular basis of HNPP has been identified as a submicroscopic deletion of the 17p11.2 chromosome in exactly the same region that it is duplicated in Charcot-Marie-Tooth disease, type 1A (CMT1A). We report genetic analyses of 13 patients (belonging to 3 families) diagnosed of HNPP by means of physical examination and electrophysiologic and morphologic tests (the last in 3 cases only). Inter- and intrafamilial variation in symptomatology was studied. Some patients presented the usual clinical signs, such as recidivating brachial plexus palsy, permanent sensory polyneuropathy, foot deformities and others that might also be found in patients with CMT1A. All the patients showed electrophysiologic signs of underlying demyelinating polyneuropathy. Genetic study centered on detecting the deletion of 17p11.2 by segregation analysis with the polymorphic markers VAW409R3a (D17S122) and EW401HE (D17S61). Our results confirmed deletion at the CTM1A location of chromosome 17p11.2 in all 13 patients examined. These data suggest that the deletion of 17p11.2 plays a causal role in HNPP and that it is the most prevalent mutation in this disease; our findings constitute new evidence of the importance of the CMT1A/HNPP locus in the formation and control of peripheral myelin and in the ultimate functioning of peripheral nerves.

[The diagnosis and prevalence of locus CMT1A duplication in Charcot-Marie-Tooth disease type 1]

BACKGROUND

The Charcot-Marie-Tooth (CMT) disease or hereditary motor-sensitive neuropathy (HMSN) is the most frequent hereditary neuropathy. The demyelinated or type 1 form (CMT1) is the most frequently presented, commonly being of a dominant autosomic inheritance. CMT1 is heterogeneous genetically and the subjacent mutation found in most of the cases is a duplication of 1,500 kb in the CMT1A locus of chromosome 17p11.2. The aim of the present study was to determine the prevalence of CMT1A duplication in patients with CMT1 and evaluate its usefulness as a biological diagnostic marker.

METHODS

The study was carried out in a group of patients with HMSN who were not related, and were distributed according to the following diagnostic categories: CMT1 (n = 49), CMT2 (n = 9), untyped CMT (n = 11) and Déjérine-Sottas (DS) disease (n = 4). To detect three alleles confirming the presence of duplication the DNA of the patients was analyzed with four polymorph markers, VAW409R3a, RM11-GT, VAW412R3HEc and EW401HE localized in the CMT1A locus.

RESULTS

CMT1A duplication was found in 68.7% of the patients with CMT1 and in 27.2% of untyped CMT patients. None of the individuals in the CMT2 and DS categories showed duplication. Cases pertaining to families with dominant autosomic inheritance and genetically sporadic cases were confirmed to show a high prevalence of duplication, being of 83.3% and 85.7%, respectively.

CONCLUSIONS

Duplication of the CMT1A locus is the most prevalent mutation found in Charcot-Marie-Tooth type 1 disease. It is a specific mutation of this disease among the different forms of hereditary motor-sensitive neuropathy. This mutation is useful as a biological marker in the diagnosis of these neuropathies.

Friedreich's ataxia: an epidemiological study in Valencia, Spain, based on consanguinity analysis

Epidemiological studies performed directly on the population show a prevalence of Friedreich's ataxia (FA) from 1 to 4.7 cases/100,000 inhabitants. An indirect epidemiological approach can be achieved using genetic methods like consanguinity studies to determine the frequency of a mutated gene and the incidence of certain diseases in the population. We obtained consanguinity data of a series of FA patients in Valencia, Spain and the figures on consanguinity in the general population that were estimated according to the Archive of Dispensations given by the Catholic church for consanguineous marriages. From these data, the frequency of the FA gene was calculated as 1/127. From these data, applying the Hardy-Weinberg principle, the frequency of the carriers was 1/64 and the incidence was 6.18/100,000 live births. Assuming a life expectancy of FA of 45 years, the prevalence was 3.83/100,000 inhabitants. These figures are in the same range as those obtained in population studies.

Origin of the de novo duplication in Charcot-Marie-Tooth disease type 1A: unequal nonsister chromatid exchange during spermatogenesis

A 1.5 Mb duplication within 17p11.2 is the major mutation causing both autosomal dominant and sporadic Charcot-Marie-Tooth disease type 1A (CMT1A). An independent origin for the mutation in each family has been postulated. The proposed genetic mechanism causing the CMT1A duplication is unequal nonsister chromatid exchange at meiosis (unequal crossing-over). We studied the parental origin of the duplication in nine genetically sporadic CMT1A patients and demonstrated that in all cases the mutation was the product of an unequal nonsister chromatid exchange during spermatogenesis. The fact that only paternal de novo duplications were observed in the sporadic CMT1A patients suggests that male specific factors may be operating during spermatogenesis that either help forming the duplication and/or stabilize the duplicated chromosome.

[Disseminated encephalomyelitis. A study of 5 cases]

Five cases of acute disseminated encephalomyelitis (ADE) with a follow-up longer than 5 years are presented. The clinical picture, CT images, MR and laboratory tests, specially LCR and evoked potentials presented in a variable form. In two cases the symptoms were preceded by viral infection. The course was acute in one case while the other four evolved in a subacute form during weeks. In two patients a pseudotumoral pattern was observed in the CT and MR images leading to difficulties in the diagnosis. Clinical improvement was accompanied by a partial resolution of the lesions. Steroid treatment improved symptomatology in all the cases. Knowledge of this process may avoid the unnecessary practice of other, more aggressive tests.