Positive correlation of CTG expansion and pharyngoesophageal alterations in myotonic dystrophy patients

Disturbance of the human gut microbiota in patients with Myotonic Dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a rare autosomal dominant genetic disorder. Although DM1 is primarily characterized by progressive muscular weakness, it exhibits many multisystemic manifestations, such as cognitive deficits, cardiac conduction abnormalities, and cataracts, as well as endocrine and reproductive issues. Additionally, the gastrointestinal (GI) tract is frequently affected, encompassing the entire digestive tract. However, the underlying causes of these GI symptoms remain uncertain, whether it is biomechanical problems of the intestine, involvement of bacterial communities, or both. The primary objective of this study is to investigate the structural changes in the gut microbiome of DM1 patients. To achieve this purpose, 35 patients with DM1 were recruited from the DM-Scope registry of the neuromuscular clinic in the Saguenay-Lac-St-Jean region of the province of Québec, Canada. Stool samples from these 35 patients, including 15 paired samples with family members living with them as controls, were collected. Subsequently, these samples were sequenced by 16S MiSeq and were analyzed with DADA2 to generate taxonomic signatures. Our analysis revealed that the DM1 status correlated with changes in gut bacterial community. Notably, there were differences in the relative abundance of Bacteroidota, Euryarchaeota, Fusobacteriota, and Cyanobacteria Phyla compared to healthy controls. However, no significant shift in gut microbiome community structure was observed between DM1 phenotypes. These findings provide valuable insights into how the gut bacterial community, in conjunction with biomechanical factors, could potentially influence the gastrointestinal tract of DM1 patients.

Myotonic Dystrophies: Targeting Therapies for Multisystem Disease

Myotonic dystrophy is an autosomal dominant muscular dystrophy not only associated with muscle weakness, atrophy, and myotonia but also prominent multisystem involvement. There are 2 similar, but distinct, forms of myotonic dystrophy; type 1 is caused by a CTG repeat expansion in the DMPK gene, and type 2 is caused by a CCTG repeat expansion in the CNBP gene. Type 1 is associated with distal limb, neck flexor, and bulbar weakness and results in different phenotypic subtypes with variable onset from congenital to very late-onset as well as variable signs and symptoms. The classically described adult-onset form is the most common. In contrast, myotonic dystrophy type 2 is adult-onset or late-onset, has proximal predominant muscle weakness, and generally has less severe multisystem involvement. In both forms of myotonic dystrophy, the best characterized disease mechanism is a RNA toxic gain-of-function during which RNA repeats form nuclear foci resulting in sequestration of RNA-binding proteins and, therefore, dysregulated splicing of premessenger RNA. There are currently no disease-modifying therapies, but clinical surveillance, preventative measures, and supportive treatments are used to reduce the impact of muscular impairment and other systemic involvement including cataracts, cardiac conduction abnormalities, fatigue, central nervous system dysfunction, respiratory weakness, dysphagia, and endocrine dysfunction. Exciting preclinical progress has been made in identifying a number of potential strategies including genome editing, small molecule therapeutics, and antisense oligonucleotide-based therapies to target the pathogenesis of type 1 and type 2 myotonic dystrophies at the DNA, RNA, or downstream target level.

High frequency of gastrointestinal manifestations in myotonic dystrophy type 1 and type 2

OBJECTIVE

To analyze gastrointestinal (GI) manifestations, their progression over time, and medications being used to treat GI symptoms in a large cohort of patients with myotonic dystrophy types 1 (DM1) and 2 (DM2).

METHODS

We analyzed patient-reported data and medical records in a national registry cohort at baseline and 5 years.

RESULTS

At baseline, the majority of patients reported trouble swallowing in DM1 (55%; n = 499 of 913) and constipation in DM2 (53%; n = 96 of 180). Cholecystectomy occurred in 16.5% of patients with DM1 and 12.8% of patients with DM2, on average before 45 years of age. The use of medications indicated for gastroesophageal reflux disease was reported by 22.5% of DM1 and 18.9% of patients with DM2. Greater risk of a GI manifestation was associated with higher body mass index and longer disease duration in DM1 and female sex in DM2. At the 5-year follow-up, the most common new manifestations were trouble swallowing in patients with DM1 and constipation in patients with DM2.

CONCLUSIONS

GI manifestations were common in both DM1 and DM2, with a relatively high frequency of gallbladder removal in DM1 and DM2 occurring at a younger age compared to normative data in the literature. Studies are needed to determine the pathomechanism of how sex, weight gain, and duration of disease contribute to GI manifestations and how these manifestations affect quality of life and clinical care for patients with DM1 and DM2.

[High resolution manometry study of pharyngeal function in patients with myotonic dystrophy]

BACKGROUND

Patients with myotonic dystrophy (MD) are known to suffer from oropharyngeal dysphagia and esophageal motility disorders, which are often the cause of aspiration pneumonia. So far only little is known about the pharyngeal contractility and the function of the upper esophageal sphincter in these patients, in particular only few data are available for manometric investigations allowing assessment of the pharyngeal pressure build-up during swallowing. The aim of this study was to collect such data in patients with MD using high resolution manometry.

METHOD

In two patients with MD high resolution manometry studies were performed during swallowing and phonation to determine pressure-dependent parameters. The results were compared with normal values from healthy subjects.

RESULTS

In both patients a reduced pressure in the entire pharynx during swallowing was determined. The duration of the contraction in the velopharynx and tongue base region was shortened. The structural course of the swallowing process and the opening and closing functions of the upper esophageal sphincter were regular. During realization of closed vowels a reduced pressure build-up in the velopharyngeal region was observed.

CONCLUSION

The force of contraction and the associated pharyngeal pressure build-up during swallowing were reduced resulting in an incomplete clearing of the pharynx. Beside myopathic disorders, neuromuscular disorders also have to be considered. The functional course of the swallowing process and the swallowing pattern was retained. The reduced pressure build-up in the velopharyngeal region can be considered as the cause for rhinophonia. To evaluate the pharyngeal function in patients with MD, high resolution manometry is a useful tool for assessing the pharyngeal function besides the basic diagnostics.

Gender as a Modifying Factor Influencing Myotonic Dystrophy Type 1 Phenotype Severity and Mortality: A Nationwide Multiple Databases Cross-Sectional Observational Study

Background

Myotonic Dystrophy type 1 (DM1) is one of the most heterogeneous hereditary disease in terms of age of onset, clinical manifestations, and severity, challenging both medical management and clinical trials. The CTG expansion size is the main factor determining the age of onset although no factor can finely predict phenotype and prognosis. Differences between males and females have not been specifically reported. Our aim is to study gender impact on DM1 phenotype and severity.

Methods

We first performed cross-sectional analysis of main multiorgan clinical parameters in 1409 adult DM1 patients (>18y) from the DM-Scope nationwide registry and observed different patterns in males and females. Then, we assessed gender impact on social and economic domains using the AFM-Téléthon DM1 survey (n = 970), and morbidity and mortality using the French National Health Service Database (n = 3301).

Results

Men more frequently had (1) severe muscular disability with marked myotonia, muscle weakness, cardiac, and respiratory involvement; (2) developmental abnormalities with facial dysmorphism and cognitive impairment inferred from low educational levels and work in specialized environments; and (3) lonely life. Alternatively, women more frequently had cataracts, dysphagia, digestive tract dysfunction, incontinence, thyroid disorder and obesity. Most differences were out of proportion to those observed in the general population. Compared to women, males were more affected in their social and economic life. In addition, they were more frequently hospitalized for cardiac problems, and had a higher mortality rate.

Conclusion

Gender is a previously unrecognized factor influencing DM1 clinical profile and severity of the disease, with worse socio-economic consequences of the disease and higher morbidity and mortality in males. Gender should be considered in the design of both stratified medical management and clinical trials.

Endocrine function in 97 patients with myotonic dystrophy type 1

The aim of this study was to investigate the endocrine function and its association to number of CTG repeats in patients with myotonic dystrophy type 1 (DM1). Concentration of various hormones and metabolites in venous blood was used to assess the endocrine function in 97 patients with DM1. Correlation with CTG(n) expansion size was investigated with the Pearson correlation test. Eighteen percent of the DM1 patients had hyperparathyroidism with increased PTH compared with 0.5% in the background population. Of these, 16% had normocalcemia and 2% had hypercalcemia. An additional 3% had hypercalcemia without elevation of PTH; 7% had abnormal TSH values (2% subnormal and 5% elevated TSH levels); 5% of the patients had type 2 diabetes mellitus; 17% of the male DM1 patients had increased LH and low levels of plasma testosterone indicating absolute androgen insufficiency. Another 21% had increased LH, but normal testosterone levels, indicating relative insufficiency. Numbers of CTG repeats correlated directly with plasma PTH, phosphate, LH, and tended to correlate with plasma testosterone for males. This is the largest study of endocrine dysfunction in a cohort of Caucasian patients with DM1. We found that patients with DM1 have an increased risk of abnormal endocrine function, particularly calcium metabolism disorders. However, the endocrine dysfunction appears not to be of clinical significance in all of the cases. Finally, we found correlations between CTG(n) expansion size and plasma PTH, phosphate, and testosterone, and neck flexion strength.

Masticatory dysfunction in patients with myotonic dystrophy (type 1): a 5-year follow-up

Eight patients with myotonic dystrophy type 1, DM1 (age range 45-63 years) were followed for a period of 5 years. Two sets of data analyzing masticatory function and activities of daily living (ADL) were obtained at baseline and at 5 years. The results from both time points were compared. The number of food items considered easy to chew, maximum bite force, occlusal contact area, number of teeth, and ADLs were significantly reduced (p < 0.05) at the second assessment when compared to the first. During the intervening 5 years, six of the eight patients adopted a soft diet. These results suggest deterioration in ADLs and masticatory function of patients with DM1. Continuous evaluation of the feeding ability and the type of diet are necessary for patients with DM1.

Videofluoroscopy and swallowing studies for neurologic disease: a primer

Many patients with neurologic impairment due to stroke, multiple sclerosis, trauma, bulbar palsy, and other disorders have difficulty swallowing. Videofluoroscopy can provide important information on patterns of impairment of the swallowing mechanism, allowing important changes in patient treatment. The detailed videofluoroscopic evaluation required to provide this information is now seldom taught and is practiced by relatively few radiologists. The aim of this article is to (a) describe the indications for videofluoroscopic swallowing studies in the evaluation of patients with neurologic conditions affecting swallowing, (b) describe the techniques for evaluating the swallow mechanism with videofluoroscopy in a standardized manner, and (c) use cine videofluoroscopy to illustrate the range of abnormalities that can be demonstrated for some of these conditions and discuss the effect of patient treatment.