Myotonic dystrophy type 1 coexisting with myasthenia gravis and thymoma

AChR-seropositive myasthenia gravis in muscular dystrophy: diagnostic pitfalls and clinical management challenges

The co-occurrence of genetic myopathies with myasthenia gravis (MG) is extremely rare, however a few studies have been reported. We aim to explore the link between genetically inherited muscle disorders and immune-mediated neuromuscular junction conditions, taking into account the diagnostic and therapeutic implications posed by these combined conditions. We searched all English medical papers registered in Web of Knowledge, PubMed, Google Scholar, and Science Direct between January 1987 concerning the association between muscular dystrophies (MD) and MG, also adding three new cases to the series reported so far. Three new clinical cases in which MG concurs with oculopharyngeal muscular dystrophy (OPMD) or facioscapulohumeral muscular dystrophy (FSHD) or myotonic dystrophy type 2 (DM2) were reported. A comprehensive literature review showed that FSHD is the dystrophy most frequently associated with generalized MG. The AChR antibody titer is high and neurophysiologic tests prove to be an essential tool for the diagnosis. The association between MG and MD is rare but should not be underestimated. The presence of unusual clinical features suggest investigating additional overlapping condition, especially when a treatable disease like MG is suspected.

Inherited myopathy plus: Double-trouble from rare neuromuscular disorders

A rare disorder in the USA is one that affects <200,000 people, making inherited myopathies rare diseases. Increasing access to genetic testing has been instrumental for the diagnosis of inherited myopathies. Genetic findings, however, require clinical correlation due to variable phenotype, polygenic etiology of certain inherited disorders, and possible co-existing independent neuromuscular disorders. We searched the Mayo Clinic Rochester medical record (2004-2020) to identify adult patients carrying pathogenic variants or likely pathogenic variants in genes causative of myopathies and having a coexisting independent neuromuscular disorder classified as rare at https://rarediseases.info.nih.gov/. One additional patient was identified at Nationwide Children's hospital. Clinical and laboratory findings were reviewed. We identified 14 patients from 13 families fulfilling search criteria. Seven patients had a "double-trouble" inherited myopathy; two had an inherited myopathy with coexistent idiopathic myositis; three had an inherited myopathy with coexisting rare neuromuscular disorder of neurogenic type; a female DMD carrier had co-existing distal spinal muscular atrophy, which was featuring the clinical phenotype; and a patient with a MYH7 pathogenic variant had Sandhoff disease causing motor neuron disease. These cases highlight the relevance of correlating genetic findings, even when diagnostic, with clinical features, to allow precise diagnosis, optimal care, and accurate prognosis.

Oculopharyngeal muscular dystrophy coexisting with myasthenia gravis

Oculopharyngeal muscular dystrophy (OPMD) and myasthenia gravis are both rare conditions of different pathophysiological nature, so a fortuitous association is unlikely. However, antiacetylcholine receptor antibodies may be found in other genetic myopathies and this is probably not coincidental. Muscle fibre degeneration can induce innate immune responses that may break immune tolerance and allow the generation of autoantibodies to muscle proteins. We report a patient with atypical OPMD who also had acetylcholine receptor antibody-mediated myasthenia gravis. This report raises awareness of the diagnostic and treatment implications of the association of myasthenia gravis with genetic myopathies.

Thymoma-associated myasthenia gravis coexisting with myotonic dystrophy: a case report

BACKGROUND

Myotonic dystrophy (dystrophia myotonica [DM]) is an autosomal-dominant inheritance, and myasthenia gravis (MG) is an autoimmune disease characterized by weakness of skeletal muscles. Cases of both DM and MG are extremely rare and distinguishing DM and MG symptoms is challenging.

CASE PRESENTATION

We herein report a 49-year-old woman presenting with subacute dyspnea and muscle weakness. She had previously been diagnosed with DM 24 years earlier. Computed tomography (CT) revealed an anterior mediastinal 32-mm solid mass that was suspected of being thymoma. The clinical features and neurological examination findings confirmed the diagnosis of thymoma-associated MG coexisting with DM. Intensive treatment for MG, including surgery, resulted in an improvement in some of her neurological symptoms.

CONCLUSIONS

The symptoms of DM usually progress slowly, so the sudden exacerbation of symptoms indicates the involvement of other factors. It is important to be aware of these associations, as an early diagnosis with proper treatment will result in a better outcome.

Loss of MBNL1 induces RNA misprocessing in the thymus and peripheral blood

The thymus is a primary lymphoid organ that plays an essential role in T lymphocyte maturation and selection during development of one arm of the mammalian adaptive immune response. Although transcriptional mechanisms have been well documented in thymocyte development, co-/post-transcriptional modifications are also important but have received less attention. Here we demonstrate that the RNA alternative splicing factor MBNL1, which is sequestered in nuclear RNA foci by C(C)UG microsatellite expansions in myotonic dystrophy (DM), is essential for normal thymus development and function. Mbnl1 129S1 knockout mice develop postnatal thymic hyperplasia with thymocyte accumulation. Transcriptome analysis indicates numerous gene expression and RNA mis-splicing events, including transcription factors from the TCF/LEF family. CNBP, the gene containing an intronic CCTG microsatellite expansion in DM type 2 (DM2), is coordinately expressed with MBNL1 in the developing thymus and DM2 CCTG expansions induce similar transcriptome alterations in DM2 blood, which thus serve as disease-specific biomarkers.

Imaging of the thymus in myotonic dystrophy type 1

The occurrence of thymoma in myotonic dystrophy type 1 (DM1) has been occasionally reported, and an increased risk of tumors has been observed. We performed imaging of the thymus in 22 patients carrying DMPK expansion. Clinical examination and routine instrumental exams were performed at the same time. We observed no thymic abnormalities in 13 subjects, thymic hyperplasia in eight patients, and an invasive thymoma in one case. Subjects with thymic abnormalities did not show peculiarities as regards clinical and electrophysiological features. We observed thymoma in one patient with an expansion in the higher range. Abnormalities of the thymus including hyperplasia and thymoma can be present in DM1, but do not seem to play a major role in DM1 pathogenesis. Further studies are needed to understand if some RNA splicing factors involved in DM1 and influenced by CTG expansion size could have a role in thymocytes proliferation.

Excessive daytime sleepiness in a patient with coexisting myotonic dystrophy type 1, myasthenia gravis and Graves' disease

A 41-year-old female with history of Graves' disease, bilateral cataract, paroxysmal atrial fibrillation was admitted because of muscle weakness, daytime sleepiness, fatigability, drowsiness, bilateral eyelid ptosis, descending of head and lower jaw. On neurological examination the patient was presented with muscle weakness, muscle atrophy (in face and sternocleidomastoid muscles), features of myotonia and apocamnosis (orbicular muscles). Electromyography revealed myopathic changes, myotonic and pseudomyotonic discharges, positive repetitive nerve stimulation test in proximal muscles. Myotonic dystrophy (MD) diagnosis was confirmed by genetic testing and myasthenia gravis (MG) by a positive titer of cholinergic receptor autoantibodies. In the CSF concentration of hypocretin was significantly decreased.

Congenital myasthenic syndrome due to mutation in CHRNE gene with clinical worsening and thymic hyperplasia attributed to association with autoimmune-myasthenia gravis

We report a patient with congenital myasthenic syndrome (CMS) due to mutation in CHRNE with symptoms since the age of 4; mild to moderate fatigable weakness involved mainly ocular, bulbar and limb muscles; functional impact of the disease in their development and physical activity was modest. By the age of 34, the patient experienced gradual worsening of fatigue with dyspnoea and pronounced limb weakness, requiring significant increase of pyridostigmine. Further, a remarkable and sustained clinical improvement followed thymectomy with hyperplastic thymus. Despite of the absence of detectable antibodies to acetyl-choline receptor (AChR) (including clustered-AChR), muscle-specific kinase and low-density lipoprotein receptor-related protein-4 antibodies in the serum obtained nine years after thymectomy, the clinical, genetic and histological features are in keeping with the extremely rare association of two rare neuromuscular junction disorders - CMS and myasthenia gravis (MG). The inexistence of other conditions that could potentially associate with thymic hyperplasia also supports the diagnosis of MG.

The coexistence of myasthenia gravis and myotonic dystrophy type 2 in a single patient

Background

Myasthenia gravis (MG) and myotonic dystrophy type 2 (DM2) are rare disorders individually, and their coexistence in the same patient is very rare. We present a patient in which these two diseases coexisted.

Case Report

The patient complained of diplopia, fluctuating limb weakness, and difficulties in swallowing and speaking. A neurological examination revealed diplopia, facial, weakness of the neck and proximal limb muscles, dysphagia, dysphonia, and myotonia. The patient's mother had DM2 and her maternal grandfather had cataracts. MG was confirmed in our patient by positive results for neostigmine and a repetitive nerve stimulation test, and elevated serum anti-acetylcholine-receptor antibodies, while DM2 was confirmed by electromyography and genetic testing. The patient improved remarkably after treatment with anticholinesterases, corticosteroids, and azathioprine.

Conclusions

This is the second reported case of the coexistence of DM2 and MG in the same patient. Since the symptoms of these two diseases overlap it is very important to keep in mind the possibility of their coexistence, so that MG is not overlooked in patients with a family history of myotonic dystrophy.

Acetylcholine receptor antibodies in patients with genetic myopathies: clinical and biological significance

We report two patients with facioscapulohumeral muscular dystrophy (FSHD) presenting with atypical clinical features. Both were found to have antibodies to acetylcholine receptor (AChR-abs) and improved with immunosuppression. AChR-abs have also been reported in patients with other genetic myopathies and it is unlikely that the association is coincidental. There is increasing evidence that muscle fibre degeneration can cause innate immune responses (autoinflammation) that may lead to the breaking of immune tolerance and the generation of autoantibodies to muscle proteins. We compare and contrast this process with the pathogenesis of archetypical myasthenia gravis.

Impact of biopsychosocial factors on chronic pain in persons with myotonic and facioscapulohumeral muscular dystrophy

To assess the role of biopsychosocial factors in patients with type 1 myotonic and facioscapulohumeral muscular dystrophy (MMD1/FSHD) with chronic pain. Associations between psychosocial factors were found to be important in other samples of persons with pain and both psychological functioning and pain interference in a sample of patients suffering from MMD/FSHD. Prospective, multiple group, survey study of 182 patients with confirmed MMD1 and FSHD. Participants completed surveys assessing pain interference and psychological functioning, as well as psychosocial, demographic, and injury-related variables. Analyses indicated that greater catastrophizing was associated with increased pain interference and poorer psychological functioning, pain attitudes were significantly related to both pain interference and psychological functioning, and coping responses were significantly related only to pain interference. In addition, greater perceived social support was associated with better psychological functioning. The results support the use of studying pain in persons with MMD/FSHD from a biopsychosocial perspective, and the importance of identifying psychosocial factors that may play a role in the adjustment to and response to pain secondary to MMD/FSHD.