Large scale genotype-phenotype analyses indicate that novel prognostic tools are required for families with facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy has been genetically linked to reduced numbers (≤ 8) of D4Z4 repeats at 4q35 combined with 4A(159/161/168) DUX4 polyadenylation signal haplotype. However, we have recently reported that 1.3% of healthy individuals carry this molecular signature and 19% of subjects affected by facioscapulohumeral muscular dystrophy do not carry alleles with eight or fewer D4Z4 repeats. Therefore, prognosis for subjects carrying or at risk of carrying D4Z4 reduced alleles has become more complicated. To test for additional prognostic factors, we measured the degree of motor impairment in a large group of patients affected by facioscapulohumeral muscular dystrophy and their relatives who are carrying D4Z4 reduced alleles. The clinical expression of motor impairment was assessed in 530 subjects, 163 probands and 367 relatives, from 176 unrelated families according to a standardized clinical score. The associations between clinical severity and size of D4Z4 allele, degree of kinship, gender, age and 4q haplotype were evaluated. Overall, 32.2% of relatives did not display any muscle functional impairment. This phenotype was influenced by the degree of relation with proband, because 47.1% of second- through fifth-degree relatives were unaffected, whereas only 27.5% of first-degree family members did not show motor impairment. The estimated risk of developing motor impairment by age 50 for relatives carrying a D4Z4 reduced allele with 1-3 repeats or 4-8 repeats was 88.7% and 55%, respectively. Male relatives had a mean score significantly higher than females (5.4 versus 4.0, P = 0.003). No 4q haplotype was exclusively associated with the presence of disease. In 13% of families in which D4Z4 alleles with 4-8 repeats segregate, the diagnosis of facioscapulohumeral muscular dystrophy was reported only in one generation. In conclusion, this large-scale analysis provides further information that should be taken into account when counselling families in which a reduced allele with 4-8 D4Z4 repeats segregates. In addition, the reduced expression of disease observed in distant relatives suggests that a family's genetic background plays a role in the occurrence of facioscapulohumeral muscular dystrophy. These results indicate that the identification of new susceptibility factors for this disease will require an accurate classification of families.

A standardized clinical evaluation of patients affected by facioscapulohumeral muscular dystrophy: The FSHD clinical score.

To define numerically the clinical severity of facioscapulohumeral muscular dystrophy (FSHD), we developed a protocol that quantifies muscle weakness by combining the functional evaluation of six muscle groups affected in this disease. To validate reproducibility of the protocol, 69 patients were recruited. Each patient was evaluated by at least five neurologists, and an FSHD severity score was given by each examiner. The degree of agreement among clinicians' evaluations was measured by kappa-statistics. Nineteen subjects received a score between 0 and 1, 9 had a score between 2 and 4, 20 received a score between 5 and 10, and 8 had a score between 11 and 15. Of the 13 subjects with D4Z4 alleles within the normal range (ranging from 10 to 150 repeats), 12 obtained a score of 0 and only 1 had a score of 1. Kappa-statistics showed a very high concordance for all muscle groups. We developed a simple, reliable, easily used tool to define the clinical expression of FSHD. Longitudinal studies will assess its sensitivity and utility in measuring changes for widespread use.

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.

Facioscapulohumeral muscular dystrophy: a multicenter study on hearing function.

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant progressive myopathy, characteristically associated with a 4q35 deletion. In the unusual infantile-onset form of this degenerative disease, sensorineural hearing loss is a frequent clinical manifestation, whereas in patients with typical late-onset FSHD, investigations regarding hearing impairment yielded controversial results. We describe the findings of a multicenter investigation on possible auditory impairment in a series of 73 FSHD patients with a genetically confirmed diagnosis. Among them, 49 cases with no risk factors for deafness, aside from the disease, were identified by a clinical questionnaire and otoscopic examination (mean age 37.8 years, 31 males and 18 females). These subjects were evaluated by pure-tone audiometry. None were aware of hearing loss, while 4 had raised unilateral or bilateral pure-tone audiometric thresholds at 4000 and 8000 Hz, when evaluated by standardized tables. However, the mean raw pure-tone audiometric threshold values for these 49 cases were not significantly different from those of 55 controls (mean age 37.1 years, 32 males and 23 females). Moreover, by statistical analysis, age of onset, degree of muscular weakness and 4q35 EcoRI fragment size made no significant difference to auditory thresholds in our FSHD patients. Overall, the results of our multicenter study suggest that hearing loss in typical FSHD is not more prevalent than in the normal population.

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

INTRODUCTION: FacioScapuloHumeral 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 METHODS: We 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 25 kb (range: 11-38). RESULTS: Typical 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. CONCLUSION: FSHD 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.

Facioscapulohumeral muscular dystrophy and occurrence of heart arrhythmia.

BACKGROUND: Subjects with facioscapulohumeral muscular dystrophy (FSHD) do not generally suffer from significant cardiac symptoms. Although with heterogeneous results, studies reported to date indicate that heart alterations unrelated to cardiomyopathy are possible in FSHD. PATIENTS AND METHODS: We describe the findings of a multicenter investigation aimed at detecting cardiac abnormalities in 83 FSHD patients, 44 males and 39 females with a mean age of 47 years. All patients underwent clinical heart examination, 12-lead electrocardiography and 24-hour Holter monitoring; echocardiography was also performed on most patients. RESULTS: Among the 83 patients, 62 with no cardiovascular risk factors were identified. Ten of them manifested clinical or subclinical cardiac involvement: 5 reported symptoms represented mostly by frequent palpitations secondary to supraventricular arrhythmia and another 5 exhibited electrocardiographic signs of short runs of supraventricular paroxysmal tachycardia. In the absence of cardiovascular risk factors, we found symptoms or signs of heart involvement of mainly arrhythmic origin in 10 of our 83 FSHD patients (12%). CONCLUSIONS: Considering our data and those available in the literature as a whole, arrhythmic alterations seem to be detected more frequently than expected in FSHD patients.