Myoimaging in the NGS era: the discovery of a novel mutation in MYH7 in a family with distal myopathy and core-like features--a case report.

BACKGROUND: Myosin heavy chain 7 related myopathies are rare disorders characterized by a wide phenotypic spectrum and heterogeneous pathological features. In the present study, we performed clinical, morphological, genetic and imaging investigations in three relatives affected by autosomal dominant distal myopathy. Whilst earlier traditional Sanger investigations had pointed to the wrong gene as disease causative, next-generation sequencing allowed us to obtain the definitive molecular genetic diagnosis in the family. CASE PRESENTATION: The proposita, being found to harbor a novel heterozygous mutation in the RYR1 gene (p.Glu294Lys), was initially diagnosed with core myopathy. Subsequently, consideration of muscle magnetic resonance imaging (MRI) features and extension of family study led this diagnosis to be questioned. Use of next-generation sequencing analysis identified a novel mutation in the MYH7gene (p.Ser1435Pro) that segregated in the affected family members. CONCLUSIONS: This study identified a novel mutation in MYH7 in a family where the conclusive molecular diagnosis was reached through a complicated path. This case report might raise awareness, among clinicians, of the need to interpret NGS data in combination with muscle MRI patterns so as to facilitate the pinpointing of the main molecular etiology in inherited muscle disorders.

An Age-Standardized Prevalence Estimate and a Sex and Age Distribution of Myotonic Dystrophy Types 1 and 2 in the Rome Province, Italy.

BACKGROUND: Prevalence estimates for the 2 forms of myotonic dystrophy types 1 and 2 (DM1 and DM2) are not exhaustive or non-available. Our aim was to estimate the minimum prevalence of DM1 and DM2 in Italy in the Rome province, applying standards of descriptive epidemiology. METHODS: All patients with a molecular diagnosis of DM1/DM2 and residents in the Rome province in 2013 have been enrolled, and the age-standardized prevalence has been calculated, assuming a Poisson distribution and adjusting for age. RESULTS: We identified 395 DM1 patients: the age-standardized prevalence for total, females and males was 9.65, 8.35 and 11.07/100,000, respectively. The mean age of subjects differed considerably according to CTG repeat length (p = 0.001). Forty DM2 patients were identified. The age-standardized prevalence for total, females and males was 0.99, 1.07 and 0.90/100,000, respectively. The mean age was 57.05. CONCLUSIONS: We estimated for the first time the age-standardized prevalence and the sex and age distribution of DM1 and DM2 in a general population. A higher prevalence of males in DM1 and females in DM2 and a higher mean age of DM2 patients (+8 years) were ascertained. Prevalence of DM2 was 10% that of DM1. These prevalence values are probably lower than mutational rates due to the incomplete penetrance of DM1 mutations and to the clinical elusiveness of DM2. Our findings will be useful in designing cohort studies and for developing a disease registry.

Brain Connectomics' Modification to Clarify Motor and Nonmotor Features of Myotonic Dystrophy Type 1.

The adult form of myotonic dystrophy type 1 (DM1) presents with paradoxical inconsistencies between severity of brain damage, relative preservation of cognition, and failure in everyday life. This study, based on the assessment of brain connectivity and mechanisms of plasticity, aimed at reconciling these conflicting issues. Resting-state functional MRI and graph theoretical methods of analysis were used to assess brain topological features in a large cohort of patients with DM1. Patients, compared to controls, revealed reduced connectivity in a large frontoparietal network that correlated with their isolated impairment in visuospatial reasoning. Despite a global preservation of the topological properties, peculiar patterns of frontal disconnection and increased parietal-cerebellar connectivity were also identified in patients' brains. The balance between loss of connectivity and compensatory mechanisms in different brain networks might explain the paradoxical mismatch between structural brain damage and minimal cognitive deficits observed in these patients. This study provides a comprehensive assessment of brain abnormalities that fit well with both motor and nonmotor clinical features experienced by patients in their everyday life. The current findings suggest that measures of functional connectivity may offer the possibility of characterizing individual patients with the potential to become a clinical tool.

Neuromuscular transmission abnormalities in myotonic dystrophy type 1: A neurophysiological study.

OBJECTIVES: Weakness and fatigue are frequent symptoms in myotonic dystrophy type 1 (DM1), mainly as a result of muscle impairment. However, neuromuscular junction (NMJ) abnormalities could play an additional role in determining these manifestations. We aimed to document the possible NMJ involvement in DM1. PATIENTS AND METHODS: In order to substantiate this hypothesis we performed low rate repetitive nerve stimulation (RNS) and single fiber electromyography (SFEMG), in 14 DM1 subjects. RESULTS: RNS resulted abnormal in four patients while SFEMG revealed a pathological jitter in ten. A significative correlation was found between jitter values and decrementing response (p<0.000311; r=0.822). CONCLUSION: These results suggest a possible involvement of NMJ in DM1.

"I Know that You Know that I Know": Neural Substrates Associated with Social Cognition Deficits in DM1 Patients.

Myotonic dystrophy type-1 (DM1) is a genetic multi-systemic disorder involving several organs including the brain. Despite the heterogeneity of this condition, some patients with non-congenital DM1 can present with minimal cognitive impairment on formal testing but with severe difficulties in daily-living activities including social interactions. One explanation for this paradoxical mismatch can be found in patients' dysfunctional social cognition, which can be assessed in the framework of the Theory of Mind (ToM). We hypothesize here that specific disease driven abnormalities in DM1 brains may result in ToM impairments. We recruited 20 DM1 patients who underwent the "Reading the Mind in the Eyes" and the ToM-story tests. These patients, together with 18 healthy controls, also underwent resting-state functional MRI. A composite Theory of Mind score was computed for all recruited patients and correlated with their brain functional connectivity. This analysis provided the patients' "Theory of Mind-network", which was compared, for its topological properties, with that of healthy controls. We found that DM1 patients showed deficits in both tests assessing ToM. These deficits were associated with specific patterns of abnormal connectivity between the left inferior temporal and fronto-cerebellar nodes in DM1 brains. The results confirm the previous suggestions of ToM dysfunctions in patients with DM1 and support the hypothesis that difficulties in social interactions and personal relationships are a direct consequence of brain abnormalities, and not a reaction symptom. This is relevant not only for a better pathophysiological comprehension of DM1, but also for non-pharmacological interventions to improve clinical aspects and impact on patients' success in life.

How genetics affects the brain to produce higher-level dysfunctions in myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is a multisystemic disorder dominated by muscular impairment and brain dysfunctions. Although brain damage has previously been demonstrated in DM1, its associations with the genetics and clinical/neuropsychological features of the disease are controversial. This study assessed the differential role of gray matter (GM) and white matter (WM) damage in determining higher-level dysfunctions in DM1. Ten patients with genetically confirmed DM1 and 16 healthy How genetics affects the brain to produce higher-level dysfunctions in myotonic dystrophy type 1 matched controls entered the study. The patients underwent a neuropsychological assessment and quantification of CTG triplet expansion. All the subjects underwent MR scanning at 3T, with studies including T1-weighted volumes and diffusion-weighted images. Voxel-based morphometry and tractbased spatial statistics were used for unbiased quantification of regional GM atrophy and WM integrity. The DM1 patients showed widespread involvement of both tissues. The extent of the damage correlated with CTG triplet expansion and cognition. This study supports the idea that genetic abnormalities in DM1mainly target the WM, but GM involvement is also crucial in determining the clinical characteristics of DM1.

Abnormal functional brain connectivity and personality traits in myotonic dystrophy type 1.

IMPORTANCE: Myotonic dystrophy type 1 (DM1), the most common muscular dystrophy observed in adults, is a genetic multisystem disorder affecting several other organs besides skeletal muscle, including the brain. Cognitive and personality abnormalities have been reported; however, no studies have investigated brain functional networks and their relationship with personality traits/disorders in patients with DM1. OBJECTIVE: To use resting-state functional magnetic resonance imaging to assess the potential relationship between personality traits/disorders and changes to functional connectivity within the default mode network (DMN) in patients with DM1. DESIGN, SETTING, AND PARTICIPANTS: We enrolled 27 patients with genetically confirmed DM1 and 16 matched healthy control individuals. Patients underwent personality assessment using clinical interview and Minnesota Multiphasic Personality Inventory-2 administration; all participants underwent resting-state functional magnetic resonance imaging. Investigations were conducted at the Istituto di Ricovero e Cura a Carattere Scientifico Santa Lucia Foundation, Catholic University of Sacred Heart, and Azienda Ospedaliera San Camillo Forlanini. INTERVENTION: Resting-state functional magnetic resonance imaging. MAIN OUTCOMES AND MEASURES: Measures of personality traits in patients and changes in functional connectivity within the DMN in patients and controls. Changes in functional connectivity and atypical personality traits in patients were correlated. RESULTS: We combined results obtained from the Minnesota Multiphasic Personality Inventory-2 and clinical interview to identify a continuum of atypical personality profiles ranging from schizotypal personality traits to paranoid personality disorder within our DM1 patients. We also demonstrated an increase in functional connectivity in the bilateral posterior cingulate and left parietal DMN nodes in DM1 patients compared with controls. Moreover, patients with DM1 showed strong associations between DMN functional connectivity and schizotypal-paranoid traits. CONCLUSIONS AND RELEVANCE: Our findings provide novel biological evidence that DM1 is a clinical condition that also involves an alteration of functional connectivity of the brain. We speculate that these functional brain abnormalities, similarly to frank psychiatric disorders, may account for the atypical personality traits observed in patients with DM1.

Spinal muscular atrophy genotyping by gene dosage using multiple ligation-dependent probe amplification.

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by degeneration of the anterior horn cells of the spinal cord, causing symmetric proximal muscle weakness. SMA is classified in three clinical types, SMA I, SMA II, and SMA III, based on the severity of the symptoms and the age of onset. About 95% of SMA cases are caused by homozygous deletion of the survival motor neuron 1 (SMN1) gene (5q13), or its conversion to SMN2. The molecular diagnosis of this disease is usually carried out by a polymerase chain reaction-restriction fragment length polymorphism approach able to evidence the absence of both SMN1 copies. However, this approach is not able to identify heterozygous healthy carriers, which show a very high frequency in general population (1:50). We used the multiple ligation-dependent probe amplification (MLPA) approach for the molecular diagnosis of SMA in 19 affected patient and in 57 individuals at risk to become healthy carriers. This analysis detected the absence of the homozygous SMN1 in all the investigated cases, and allowed to discriminate between SMN1 deletion and conversion to SMN2 on the basis of the size showed by the peaks specific for the different genes mapped within the SMA critical region. Moreover, MLPA analysis evidenced a condition of the absence of the heterozygous SMN1 in 33 out of the 57 relatives of the affected patients, demonstrating the usefulness of this approach in the identification of healthy carriers. Thus, the MLPA technique represents an easy, low cost, and high throughput system in the molecular diagnosis of SMA, both in affected patients and in healthy carriers.

Instability of a premutation allele in homozygous patients with myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is caused by the expansion of an unstable CTG repeat in the DMPK gene on chromosome 19q13.3. We present two siblings with DM1 who each inherited a premutation allele, (CTG)43, stably transmitted from the mother and a full-mutation allele, either (CTG)500 or (CTG)180, derived from a paternal protomutation allele, (CTG)52. Small-pool polymerase chain reaction analysis showed that the (CTG)52 repeat allele was relatively stable in somatic tissues but was highly unstable in the male germline and extremely biased toward further expansion, consistent with the high levels of anticipation observed in DM1 families. The (CTG)43 allele showed subtle somatic instability in the mother, with maximum additions of two repeats and deletions of one repeat. Conversely, in the younger affected siblings the (CTG)43 allele showed a high degree of somatic instability (approximately 70% mutation load), resulting in deletions reverting to the high end of the normal range (down to [CTG]33) and additions up to the proto-mutation range (up to [CTG]64). The difference in the somatic stability of the (CTG)43 allele between the mother and her offspring suggests that interallelic interactions or other mechanisms in trans regulate the stability of the (CTG)43 premutation allele.