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

Keywords: epilepsy; facioscapulohumeral muscular dystrophy; genetics; hearing loss; mental retardation; review Background and purpose:\u2002 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\u201313 kb) focusing on hearing loss, a still debated FSHD extramuscular manifestation. Patients and methods:\u2002 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:\u2002 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:\u2002 Hearing loss represents a characteristic feature of FSHD patients with a large 4q35 deletion. Moreover, when considering only cases with 10\u201311 kb, it appears to be associated with early-onset dystrophic phenotype, with mental retardation (92%) and possibly with epilepsy (58%)

Comparative transcriptional and biochemical studies in muscle of myotonic dystrophies (DM1 and DM2)

Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (proximal muscular myopaty/DM2) are caused by similar dynamic mutations at two distinct genetic loci. The two diseases also lead to similar phenotypes but different clinical severity. Dysregulation of alternative splicing has been suggested as the common pathogenic mechanism. Here, we investigate the molecular differences between DM1 and DM2 using reverse transcriptase-polymerase chain reaction of troponin T (TnT) and the insulin receptor (IR), as well as immunoblotting of TnT in muscle biopsies from DM1 and DM2 patients. We found that: (a) slow TnT was encoded by two different transcripts in significantly different ratios in DM1 and DM2 muscles; (b) DM2 muscles exhibited a higher degree of alternative splicing dysregulation for fast TnT transcripts when compared to DM1 muscles; (c) the distribution of TnT proteins was significantly skewed towards higher molecular weight species in both diseases; (d) the RNA for the insulin-independent IR-A isoform was significantly increased and appeared related to the fibre-type composition in the majority of the cases examined. On the whole, these data should give a better insight on pathogenesis of DM1 and DM2

Prevalence of Inherited Ataxias in Province of Padua, Italy

Few population studies are available on epidemiological indexes of hereditary ataxias. An investigation on the prevalence rate of these movement disorders is in progress for the Veneto region, the main area of northeast Italy with a population of 4,490,586 inhabitants. The first results of this epidemiological survey concern the province of Padua, which numbers 845,203 residents (January 1, 2002). The prevalence rate of inherited ataxias has been estimated at 93.3 cases per million inhabitants. The most common types appeared to be the autosomal dominant forms, namely spinocerebellar ataxia type 1 and 2, with a prevalence of 24 per 1,000,000. In the same population, with a prevalence rate of 6 per 1,000,000, Friedreich's ataxia was defined as the prominent recessive autosomal form. There were very rare cases of ataxia telangiectasia, ataxia with vitamin E deficiency and cerebellar ataxia with congenital muscular dystrophy, a recently identified autosomal recessive disease

Atypical onset in a series of 122 cases with FacioScapuloHumeral Muscular Dystrophy

AbstractIntroductionFacioScapuloHumeral Muscular Dystrophy (FSHD), a disease linked to a heterozygous D4Z4 deletion on chromosome 4q35, typically starts with shoulder-girdle and facial muscle involvement. Atypical presentations have occasionally been reported, but their frequency has still not been defined.Patients and methodsWe studied the occurrence rate of FSHD with atypical onset in 122 symptomatic subjects from 76 unrelated families with genetically confirmed FSHD. These 75 males and 47 females, with a mean age of 49 years (range: 11–85), had a mean EcoRI fragment of 25kb (range: 11–38).ResultsTypical shoulder-girdle or facial weakness at onset was reported by 88 patients (72%). Unusual presentations included: foot drop in 16 (13%) and proximal lower limb weakness in eight patients (7%). Two cases at onset manifested quite atypical, apparently non-FSHD-related syndromes: a 42-year-old woman presented with infantile epilepsy and a 41-year-old man with myoglobinuria. In the latter patient, DNA analysis detected a 4q35 deletion associated to an heterozygous CAPN3 mutation.ConclusionFSHD presentation with foot drop or lower limb proximal weakness appeared to be more frequent than expected. This type of weakness at onset has to be considered premature, but still representative of disease-related muscle involvement. Quite atypical onset appears very rare and calls for further investigation on non-FSHD-related etiology