Facioscapulohumeral muscular dystrophy: epidemiological and molecular study in a north-east Italian population sample.

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disease associated with a partial deletion on chromosome 4q35. Few relevant investigations have been reported on its epidemiology and were essentially based on clinical diagnosis, having been performed before recognition of the molecular mutation. We report an epidemiological survey on FSHD patients, in which the diagnosis was obtained by combined clinical and molecular evaluation. The survey concerned the north-east Italian province of Padova, an area of 871,190 inhabitants (1 January 2004). We identified 40 patients affected by FSHD based on clinical diagnosis. In 33 of them, the EcoRI fragment size in the 4q35 region ranged from 14 to 35 kb. Four other patients belonging to the same family harbored a 38-kb fragment. In these four cases, the relationship between the borderline deletion with the mild FSHD phenotype was corroborated by additional haplotype reconstruction and segregation analysis. Interestingly, the same mild facial-sparing clinical pattern was apparent only in one other patient with an EcoRI fragment of 32 kb, suggesting that this unusual FSHD phenotype may be due to very small 4q35 deletions. On the whole, estimating a prevalence rate of 44 x 10(-6), our survey confirmed FSHD as one of the most frequent neuromuscular disorders in Western populations.

POMT1 and POMT2 mutations in CMD patients: a multicentric Italian study.

Mutations in POMT1 and POMT2 genes were originally identified in Walker-Warburg syndrome (WWS) and subsequently reported in patients with milder phenotypes characterised by mental retardation with or without brain abnormalities and without ocular malformations. As part of a multicentric Italian study we screened the POMT1 and POMT2 genes in 61 congenital muscular dystrophy (CMD) patients with alpha-dystroglycan reduction on muscle biopsy and/or clinical and radiological findings suggestive of the known forms of CMD with alpha-dystroglycan deficiency. The aim of the study was to establish how frequently mutations in POMT1 and POMT2 occur in CMD patients in the Italian population and to evaluate the spectrum of associated phenotypes. Thirteen patients showed mutations in POMT1 and five harboured mutations in POMT2, accounting for a total of 20 different mutations, eight of which were novel (two in POMT1 and six in POMT2). Normal brain MRI associated with mental retardation and microcephaly was the most frequent finding in patients with mutations in POMT1 (six out of 13), but was also found in a patient with POMT2 mutations. Predominant cerebellar hypoplasia was also frequent both in patients with POMT1 (three out of 13) and POMT2 (three out of 5) mutations. A MEB phenotype with frontal cortical dysplasia and pons abnormalities was found in two patients with POMT1 and in one with POMT2 mutations, while a WWS phenotype was only found in a case with mutations in POMT1. Mutations causing frameshifts and stop codons were responsible for the more severe phenotypes. Our results provide further evidence that, as previously reported for FKRP, the array of mutations in POMT1 and POMT2 is ample and the spectrum of associated phenotypes is wider than initially thought.

Facioscapulohumeral muscular dystrophy: hearing loss and other atypical features of patients with large 4q35 deletions.

BACKGROUND AND PURPOSE: Patients affected by facioscapulohumeral muscular dystrophy (FSHD) with unusual large 4q35 deletions tend to present atypical features in early childhood. We explored the clinical presentation of patients with a very short 4q35 fragment (10-13 kb) focusing on hearing loss, a still debated FSHD extra-muscular manifestation. PATIENTS AND METHODS: We evaluated six cases with EcoRI 4q35 fragment size ranging from 10 to 13 kb. Assessment of hearing function was carried out by otoscopy, audiometry and auditory-evoked brainstem responses (ABR). Patient data were compared with those of 28 similar subjects reported in the literature. RESULTS: Sensorineural hearing loss was found in four patients, who presented infantile-onset dystrophic phenotype. Hearing loss was associated with mental retardation in three of them and with epilepsy in two. Auditory ability of the other two cases was mildly impaired. If findings related to 28 similar cases reported to date are also considered, auditory impairment appears evident in 68% of these subjects. CONCLUSIONS: Hearing loss represents a characteristic feature of FSHD patients with a large 4q35 deletion. Moreover, when considering only cases with 10-11 kb, it appears to be associated with early-onset dystrophic phenotype, with mental retardation (92%) and possibly with epilepsy (58%).

Exploring mental status in Friedreich's ataxia: a combined neuropsychological, behavioral and neuroimaging study.

Despite much evidence of cognitive and affective disorders in Friedreich's ataxia (FRDA), the nature of mental status in FRDA has received little systematic attention. It has been proposed that the cerebellum may interfere indirectly with cognition through the cerebello-cortical loops, whereas the role of pathological changes in different areas of the central nervous system is still undetermined. In the present study, 13 patients with molecularly determined FRDA and a group of matched controls were evaluated by a comprehensive battery of neuropsychological tests and the Minnesota Multiphasic Personality Inventory. A repetitive task of simple visual-reaction times was used to investigate implicit learning in all subjects. Pathological changes in cortical areas were explored comparing cerebral activations of patients and controls during finger movements (functional MRI). The intelligence profile of FRDA patients is characterized by concrete thinking, poor capacity in concept formation and visuospatial reasoning. FRDA patients show reduced speed of information processing. The learning effect seen in controls was notably absent in patients with FRDA. The patients' personality is characterized by some pathological aspects and reduced defensiveness. Patterns of cortical activation during finger movements are heterogeneous in patients compared to controls. Cognitive impairment, mood disorders and motor deficits in FRDA patients may be the result of the cumulative damage caused by frataxin deficiency not only in the cerebellum and spinal cord but also in other brain areas.

Genetic mapping of a susceptibility locus for disc herniation and spastic paraplegia on 6q23.3-q24.1.

It has been suggested that a genetic factor(s) or a familial predisposition may contribute to the clinical manifestations of disc herniation; moreover, no genetic linkage between spinal disc herniation and spastic paraplegia has ever been described. A family with consanguineous parents and four of eight sibs affected by multiple disc herniations and spastic paraplegia was clinically and genetically analysed. Surgery caused partial improvement in all of them. After the exclusion of type II collagen and vitamin D receptor genes and the recessive loci for HSPs, a genome wide search was performed with about 500 fluorescent markers. Positive lod score values were obtained for chromosome 6q22.31-q24.1, with evidence of three homozygous intervals. The maximum multipoint lod score of 3.28 was obtained in only one interval, between markers D6S1699 and D6S314. On the whole, a susceptibility locus for disc herniation and autosomal recessive spastic paraplegia was found on chromosome 6q23.3-q24.1. This is the first time that disc herniation and the associated neurological syndrome has been linked to a human chromosomal region.

Molecular diagnosis in LGMD2A: mutation analysis or protein testing?

Limb girdle muscular dystrophy (LGMD) type 2A (LGMD2A) is caused by mutations in the CAPN3 gene encoding for calpain-3, a muscle specific protease. While a large number of CAPN3 gene mutations have already been described in calpainopathy patients, the diagnosis has recently shifted from molecular genetics towards biochemical assay of defective protein. However, an estimate of sensitivity and specificity of protein analysis remains to be established. Thus, we first correlated protein and molecular data in our large LGMD2A patient population. By a preliminary immunoblot screening for calpain-3 protein of 548 unclassified patients with various phenotypes (LGMD, myopathy, or elevated levels of serum creatine kinase [hyperCKemia]), we selected 208 cases for CAPN3 gene mutation analysis: 69 had protein deficiency and 139 had normal expression. Mutation search was conducted using SSCP, denaturing high performance liquid chromatography (DHPLC), amplification refractory mutation system (ARMS-PCR), and direct sequencing methods. We identified 58 LGMD2A mutant patients: 46 (80%) had a variable degree of protein deficiency and 12 (20%) had normal amount of calpain-3. We calculated that the probability of having LGMD2A is very high (84%) when patients show a complete calpain-3 deficiency and progressively decreases with the amount of protein; this new data offers an important tool for genetic counseling when only protein data are available. A total of 37 different CAPN3 gene mutations were detected, 10 of which are novel. In our population, 87% of mutant alleles were concentrated in seven exons (exons 1, 4, 5, 8, 10, 11, and 21) and 61% correspond to only eight mutations, indicating the regions where future molecular analysis could be restricted. This study reports the largest collection of LGMD2A patients so far in which both protein and gene mutations were obtained to draw genotype-protein-phenotype correlations and provide insights into a critical protein domain.

Exercise-induced recurrent myoglobinuria: defective activity of inner carnitine palmitoyltransferase in muscle mitochondria of two patients.

In carnitine palmitoyltransferase (CPT) deficiency, it is not known whether the outer (CPT-I) and the inner (CPT-II) mitochondrial activities are equally altered. By two different assays, we found that CPT activity in fresh intact mitochondria of two patients was normal or increased, indicating an active outer CPT. In controls and in one of the two patients, the isotope-exchange assay was also evaluated after disruption of mitochondria by sonication: in controls the activity almost doubled because of the contribution of inner CPT to the assay, but in the patients it did not increase, indicating absence of the CPT-II activity. After further disruption of mitochondria by freezing and all-glass homogenization, CPT activity in patients decreased to 36% and 10% of control. These data suggest CPT deficiency was limited to the inner mitochondrial activity. The alteration could be explained by mutation of the membrane factor that determines in situ differences between CPT-I and II.

Myoglobinuria and carnitine palmityltransferase (CPT) deficiency: studies with malonyl-CoA suggest absence of only CPT-II.

A 23-year-old man suffered since adolescence from recurrent myoglobinuria. His ketone body production during fasting was normal. Muscle, liver, and platelet carnitine palmityltransferase (CPT) ranged from 4 to 27% of control by isotope exchange and backward assays. Forward CPT activity was 34% of control in liver, whereas in muscle and platelets it was either normal or absent depending on the experimental conditions. CPT residual activity was studied with malonyl-CoA, a physiologic inhibitor of CPT-I (sensitive fraction) in rat liver mitochondria. In our patient, the insensitive fraction was missing in muscle, liver, and platelets, while the sensitive fraction was increased considerably in the same tissues. Similar results were obtained in platelets of two other patients with CPT deficiency. Increased malonyl-CoA sensitive CPT and decreased malonyl-CoA insensitive CPT suggest absence of only the CPT-II isoenzyme in these patients.

A novel laminin alpha2 isoform in severe laminin alpha2 deficient congenital muscular dystrophy.

OBJECTIVES: Laminin alpha2 deficiency presents at birth with muscle weakness, hypotonia, and usually asymptomatic white matter signal on MRI. Few patients with laminin alpha2 deficiency have been described with seizures and structural brain abnormalities. The reason for the variation in the severity of the clinical phenotype in congenital muscular dystrophy (CMD) with laminin alpha2 deficiency is not known. METHODS: A patient with CMD with partial laminin alpha2 presenting with brain structural abnormalities and untreatable generalized and partial complex seizure was studied. Alternative laminin alpha2 splicing was studied by single-strand conformational polymorphism/sequencing analysis. RESULTS: A novel laminin alpha2 isoform was identified. Nonsense laminin alpha2 mutations (stop codons) were inherited from both parents; however, one of the nonsense mutations was in a region of exon 31, which is alternatively spliced. The alternatively spliced isoform excluded one of the stop codon mutations, and was thus able to produce normal laminin alpha2 corresponding to this isoform. Laminin alpha2 immunofluorescence showed that this isoform was not evenly distributed at the muscle fiber basal lamina, but preferentially localized in discrete areas. Laminin alpha5, beta1, gamma1, and nidogen showed decreased expression by immunofluorescence. CONCLUSIONS: The severity of this patient's phenotype may be due to overexpression of the exon 31-spliced laminin alpha2 isoform. Exon 31 lies in the IIIA domain of the laminin alpha2 protein, just proximal to the triple coil-coiled region. It is possible that chain assembly is impaired by this isoform, resulting in a loss of possible rescue mechanisms.

Laminin alpha2 muscular dystrophy: genotype/phenotype studies of 22 patients.

OBJECTIVE: To determine the number of primary laminin alpha2 gene mutations and to conduct genotype/phenotype correlation in a cohort of laminin alpha2-deficient congenital muscular dystrophy patients. BACKGROUND: Congenital muscular dystrophies (CMD) are a heterogeneous group of muscle disorders characterized by early onset muscular dystrophy and a variable involvement of the CNS. Laminin alpha2 deficiency has been reported in about 40 to 50% of cases of the occidental, classic type of CMD. Laminin alpha2 is a muscle specific isoform of laminin localized to the basal lamina of muscle fibers, where it is thought to interact with myofiber membrane receptor, such as integrins, and possibly dystrophin-associated glycoproteins. METHODS: Seventy-five CMD patients were tested for laminin alpha2 expression by immunofluorescence and immunoblot. The entire 10 kb laminin alpha2 coding sequence of 22 completely laminin alpha2-deficient patients was screened for causative mutations by reverse transcription (RT)-PCR/single strand conformational polymorphisms (SSCP) analysis and protein truncation test (PTT) analysis followed by automatic sequencing of patient cDNA. Clinical data from the laminin alpha2-deficient patients were collected. RESULTS: Thirty laminin alpha2-negative patients were identified (40% of CMD patients tested) and 22 of them were screened for laminin alpha2 mutations. Clinical features of laminin alpha2-deficient patients were similar, with severe floppiness at birth, delay in achievement of motor milestones, and MRI findings of white matter changes with normal intelligence. Loss-of-function mutations were identified in 95% (21/22) of the patients studied. SSCP analysis detected laminin alpha2 gene mutations in about 50% of the mutant chromosomes; PTT successfully identified 75% of the mutations. A two base pair deletion mutation at position 2,096-2,097 bp was present in 23% of the patients analyzed. CONCLUSIONS: Our data suggest that the large majority of laminin alpha2-deficient patients show laminin alpha2 gene mutations.

Clinical and neuroimaging study of central nervous system in congenital myotonic dystrophy.

We present the clinical and neuroimaging findings of five patients (four males, one female; mean age 12 years) affected by congenital myotonic dystrophy and the correlation with their molecular genetic analysis. At birth all five presented severe muscular weakness and hypotonia, associated with feeding difficulties and respiratory distress. In the same patients, congenital clubfoot or more generalized arthrogryposis was also evident. Lymphocyte DNA was characterized in each by a CTG repeat longer than 1300 in the region of the myotonic dystrophy gene in chromosome 19. The patients' neurological condition was evaluated by clinical examination, intelligence tests, electroencephalography, and brain magnetic resonance imaging. All five suffered from some impairment of intellectual function (IQ ranged from 52 to 79). In three a longitudinal evaluation of the cognitive deficit detected no deterioration. In all patients magnetic resonance imaging showed some degree of ventricular dilatation, loosely correlated to the cognitive impairment; in three there was hypoplasia of the corpus callosum and in two mild abnormalities of supratentorial white matter. The relationship between the size of the CTG repeat expansion found in lymphocyte DNA and the cerebral abnormalities appeared inconsistent in this unusual myoencephalopathy of the newborn.

Supplemental therapy in isolated vitamin E deficiency improves the peripheral neuropathy and prevents the progression of ataxia.

A 24-year-old male, who suffered since childhood from a progressive form of ataxia associated with peripheral neuropathy, was found severely deficient in serum vitamin E. He walked with bilateral aid and presented severe dysmetria of the limbs and dysarthric speech; muscular strength and trophism were slightly diminished in the distal muscles of four limbs and there was hypotonia of the arms; he presented absent deep tendon reflexes, bilateral Babinski's sign, reduced proprioception at four limbs, pes cavus and fasciculations of the tongue. Intestinal fat malabsorption and other gastrointestinal or haematological conditions associated with deficiency of this vitamin were ruled out. In this patient, after 2 years of a daily supplement of high doses of vitamin E, a further progression of the disease was not observed and, moreover, the neurophysiological characteristics of his neuropathy appeared clearly improved. A longitudinal evaluation of serum vitamin E levels showed values in the normal range after 13 months of therapy. The patient had molecular genetic analysis of chromosome 8 and was found homozygous for the unusual mutation 513insTT in the alpha-tocopherol transfer protein gene.

Ataxia and congenital muscular dystrophy: the follow-up of a new specific phenotype.

Cerebellar hypoplasia may, at neuroimaging studies, be found in association with congenital muscular dystrophy (CMD), although it is an extremely rare occurrence. We here report on three CMD patients who underwent a longitudinal evaluation of clinical and neuroimaging features for a mean period of 18 years. Case 1, a 22-year-old woman, and cases 2 and 3, brothers aged 26 and 20 years, respectively, had presented a mild to moderate muscular weakness and increased serum creatine kinase (CK) levels since birth. All cases were diagnosed in the first years of life, with identification of evident dystrophic changes at muscle biopsy and moderate to severe cerebellar hypoplasia at brain computed tomography (CT) scan. Subsequently, all the patients underwent a second muscle biopsy, with immunostaining and immunoblot analysis, which showed normal values for merosin, dystrophin and dystrophin-related proteins. During the longitudinal study, the patients underwent repeated neurological and psychiatric examinations, serum CK controls, intellectual ability assessments and neuroimaging evaluations (CT and/or magnetic resonance imaging (MRI)). In all cases, these investigations indicated a mild to moderate deficit in the proximal muscles and a clear-cut cerebellar syndrome which, it was assumed, had been present since the first years. The patients also presented some intellectual difficulties, with an IQ of 0.69 in case 1, 0.83 in case 2 and 0.61 in case 3. The clinical course of all the patients was static, and all symptoms of the combined muscle and brain involvement persisted. Nor were any changes in the cerebellar hypoplasia observed at repeat MRIs. Findings obtained by us on the longitudinal study and a review of the literature indicate that cerebellar hypoplasia and merosin-positive CMD constitute a particular clinical phenotype, mainly characterized by an ataxic syndrome associated with a non-severe muscular involvement and a possible mild intellectual impairment.

Reversible aphasia in adolescence: A late-onset form of Landau Kleffner syndrome? Report of a single case.

An adolescent boy developed a long-lasting pattern of global aphasia, concomitant to focal (left temporal) EEG abnormalities; this was followed by complete recovery. Laboratory and neuroimaging studies were within normal limits. The possibility of a late-onset Landau Kleffner syndrome is discussed.

Brain involvement in myotonic dystrophies: neuroimaging and neuropsychological comparative study in DM1 and DM2.

The objective of this study was to determine the degree of brain involvement in a cohort of myotonic dystrophy type 1 and type 2 (DM1, DM2) patients by brain studies and functional tests and to compare the results of the two groups. DM1, DM2 are multisystemic disorders due to polynucleotide expansions. Previous studies on brain involvement by neuroimaging and functional methods have led to contradictory results. Fifty molecularly defined DM1 patients and 14 DM2 patients, were recruited for the study. Age at recruitment, age at disease onset, disease duration and educational level were recorded. Neuromuscular assessment was done by MIRS. An extensive neuropsychological battery was performed in 48/50 DM1 and in a control group of 44 healthy matched subjects. Forty six of 50 DM1 and 12/14 DM2 underwent brain MRI; 21/50 DM1 and 9/14 DM2 underwent brain perfusion SPECT, with semiquantitative analysis of the results. MRI images were classified by ARWMC (age-related white matter changes) score, in order to quantify recurrence, localization and patterns of distribution of white matter hyperintense lesions (WMHLs) in our two cohorts. MRI results were matched to SPECT and to neuropsychological results. Thirty-seven of 46 DM1 and 10/12 DM2 had abnormal MRI imaging, showing scattered supratentorial, bilateral, symmetrical focal or diffuse WMHLs. A typical temporo-insular diffuse subcortical pattern was seen in DM1 subjects only, with no correlation with cognitive involvement. Major cognitive involvement was seen in the case of diffuse frontal lesions. A relationship with CTG expansion size was documented for DM1 subjects. SPECT showed minimal hypoperfusion in the posterior cortex planes in DM1 and, to a lesser extent, in DM2. Very mild degrees of involvement in the DM2 cohort were seen. Neuroimaging and functional investigations confirmed a more severe involvement of the brain in DM1 compared to DM2. A temporo-insular diffuse lesional pattern, specific for DM1, was found on MRI. This confirms greater expansion size as a risk factor for more extensive brain involvement in DM1.

Congenital muscular dystrophies with cognitive impairment. A population study.

BACKGROUND: Cognitive impairment has been reported in a significant proportion of patients with congenital muscular dystrophies (CMD), generally associated with brain changes. OBJECTIVES: The aim of this study was to establish 1) the overall prevalence of CMD and cognitive impairment in the Italian population; 2) the frequency of individual genetically defined forms; and 3) the presence of distinct phenotypes not associated with mutations in the known genes. METHODS: We included all patients with CMD and cognitive impairment followed in all the Italian tertiary neuromuscular centers. Clinical, brain MRI, and morphologic data were collected. Genetic screening of the known genes was performed according to clinical and muscle biopsy findings. RESULTS: Ninety-two of the 160 (58%) patients with CMD followed in our centers had cognitive impairment. alpha-Dystroglycan (alpha-DG) reduction on muscle biopsy was found in 73/92 (79%), with 42/73 carrying mutations in the known genes. Another 6/92 (7%) showed a laminin alpha2 deficiency on muscle biopsy and 5 of the 6 carried mutations in LAMA2. The remaining 13/92 (14%) patients had normal alpha-DG and laminin alpha2 expression on muscle. CONCLUSIONS: This is the first population study establishing the prevalence of CMD and cognitive impairment and providing a classification on the basis of clinical, MRI, and genetic findings. We also showed that cognitive impairment was not always associated with alpha-DG or laminin alpha2 reduction or with structural brain changes.

Anosmia associated with hearing loss and benign positional vertigo after head trauma.

It is well known that head trauma may cause hearing loss, which can be either conductive or sensorineural. Benign paroxysmal positional vertigo and olfactory dysfunction due to head trauma are also well known. The association between sensorineural hearing loss and anosmia, following head trauma, is extremely rare. Two rare cases of post-traumatic occurrence of hearing loss, olfactory dysfunction and benign positional vertigo are reported and the pathophysiology of the association between sensorineural hearing loss, anosmia and benign paroxysmal positional vertigo, after head injury, are briefly discussed. ENT specialists should, in the authors' opinion, be aware of the possible association between anosmia, sensorineural hearing loss and benign paroxysmal positional vertigo after head injury, even in the absence of skull fracture.

Congenital muscular dystrophies with defective glycosylation of dystroglycan: a population study.

BACKGROUND: Congenital muscular dystrophies (CMD) with reduced glycosylation of alpha-dystroglycan (alpha-DG) are a heterogeneous group of conditions associated with mutations in six genes encoding proven or putative glycosyltransferases. OBJECTIVES: The aim of the study was to establish the prevalence of mutations in the six genes in the Italian population and the spectrum of clinical and brain MRI findings. METHODS: As part of a multicentric study involving all the tertiary neuromuscular centers in Italy, FKRP, POMT1, POMT2, POMGnT1, fukutin, and LARGE were screened in 81 patients with CMD and alpha-DG reduction on muscle biopsy (n = 76) or with a phenotype suggestive of alpha-dystroglycanopathy but in whom a muscle biopsy was not available for alpha-DG immunostaining (n = 5). RESULTS: Homozygous and compound heterozygous mutations were detected in a total of 43/81 patients (53%), and included seven novel variants. Mutations in POMT1 were the most prevalent in our cohort (21%), followed by POMT2 (11%), POMGnT1 (10%), and FKRP (9%). One patient carried two heterozygous mutations in fukutin and one case harbored a new homozygous variant in LARGE. No clear-cut genotype-phenotype correlation could be observed with each gene, resulting in a wide spectrum of clinical phenotypes. The more severe phenotypes, however, appeared to be consistently associated with mutations predicted to result in a severe disruption of the respective genes. CONCLUSIONS: Our data broaden the clinical spectrum associated with mutations in glycosyltransferases and provide data on their prevalence in the Italian population.

Phenotypic clustering of lamin A/C mutations in neuromuscular patients.

BACKGROUND: Mutations in the LMNA gene, encoding human lamin A/C, have been associated with an increasing number of disorders often involving skeletal and cardiac muscle, but no clear genotype/phenotype correlation could be established to date. METHODS: We analyzed the LMNA gene in a large cohort of patients mainly affected by neuromuscular or cardiac disease and clustered mutated patients in two groups to unravel possible correlations. RESULTS: We identified 28 variants, 9 of which reported for the first time. The two groups of patients were characterized by clinical and genetic differences: 1) patients with childhood onset displayed skeletal muscle involvement with predominant scapuloperoneal and facial weakness associated with missense mutations; 2) patients with adult onset mainly showed cardiac disorders or myopathy with limb girdle distribution, often associated with frameshift mutations presumably leading to a truncated protein. CONCLUSIONS: Our findings, supported by meta-analysis of previous literature, suggest the presence of two different pathogenetic mechanisms: late onset phenotypes may arise through loss of function secondary to haploinsufficiency, while dominant negative or toxic gain of function mechanisms may explain the severity of early phenotypes. This model of patient stratification may help patient management and facilitate future studies aimed at deciphering lamin A/C pathogenesis.

Friedreich's ataxia: clinical heterogeneity in two sisters.

Diagnostic evaluation of two sisters affected by ataxia, with similar age of onset, revealed a characteristic trinucleotide expansion in the Friedreich's ataxia (FRDA) locus and two different phenotypic presentations. At onset the elder sister had retained deep tendon reflexes (FARR), while the younger sister presented classic FRDA. The GAA expansion in the patients' alleles proved to be similar in both siblings, ruling out that age at onset and clinical heterogeneity could be due to different FRDA mutations. On the whole, clinical and genetic data on these patients confirmed that FARR is a variant phenotype of FRDA.