Proximal myotonic myopathy

Exploring diseases and syndromes in neurology case reports from 1955 to 2017 with text mining

BACKGROUND

A large number of neurology case reports have been published, but it is a challenging task for human medical experts to explore all of these publications. Text mining offers a computational approach to investigate neurology literature and capture meaningful patterns. The overarching goal of this study is to provide a new perspective on case reports of neurological disease and syndrome analysis over the last six decades using text mining.

METHODS

We extracted diseases and syndromes (DsSs) from more than 65,000 neurology case reports from 66 journals in PubMed over the last six decades from 1955 to 2017. Text mining was applied to reports on the detected DsSs to investigate high-frequency DsSs, categorize them, and explore the linear trends over the 63-year time frame.

RESULTS

The text mining methods explored high-frequency neurologic DsSs and the relationships between them from 1955 to 2017. We detected more than 18,000 unique DsSs and found 10 categories of neurologic DsSs. While the trend analysis showed the increasing trends in the case reports for top-10 high-frequency DsSs, the categories had mixed trends.

CONCLUSION

Our study provided new insights into the application of text mining methods to investigate DsSs in a large number of medical case reports that occur over several decades. The proposed approach can be used to provide a macro level analysis of medical literature by discovering interesting patterns and tracking them over several years to help physicians explore these case reports more efficiently.

Hearing impairment in patients with myotonic dystrophy type 2

Objective

To systematically assess auditory characteristics of a large cohort of patients with genetically confirmed myotonic dystrophy type 2 (DM2).

Methods

Patients with DM2 were included prospectively in an international cross-sectional study. A structured interview about hearing symptoms was held. Thereafter, standardized otologic examination, pure tone audiometry (PTA; 0.25, 0.5, 1, 2, 4, and 8 kHz), speech audiometry, tympanometry, acoustic middle ear muscle reflexes, and brainstem auditory evoked potentials (BAEP) were performed. The ISO 7029 standard was used to compare the PTA results with established hearing thresholds of the general population according to sex and age.

Results

Thirty-one Dutch and 25 French patients with DM2 (61% female) were included with a mean age of 57 years (range 31–78). The median hearing threshold of the DM2 cohort was higher for all measured frequencies, compared to the 50th percentile of normal (p < 0.001). Hearing impairment was mild in 39%, moderate in 21%, and severe in 2% of patients with DM2. The absence of an air–bone gap with PTA, concordant results of speech audiometry with PTA, and normal findings of BAEP suggest that the sensorineural hearing impairment is located in the cochlea. A significant correlation was found between hearing impairment and age, even when corrected for presbycusis.

Conclusions

Cochlear sensorineural hearing impairment is a frequent symptom in patients with DM2, suggesting an early presbycusis. Therefore, we recommend informing about hearing impairment and readily performing audiometry when hearing impairment is suspected in order to propose early hearing rehabilitation with hearing aids when indicated.

Muscle pathology in 57 patients with myotonic dystrophy type 2

We evaluated muscle biopsies from 57 patients with genetically confirmed myotonic dystrophy type 2/proximal myotonic myopathy (DM2/PROMM). Light microscopy showed myopathic together with "denervation-like" changes in almost all biopsies obtained from four different muscles: increased fiber size variation, internal nuclei, small angulated fibers, pyknotic nuclear clumps, and predominant type 2 fiber atrophy. Quantitative morphometry in 18 biopsies that were immunostained for myosin heavy chain confirmed a predominance of nonselective type 2 fiber atrophy. These histological changes were similar in all patients regardless of the site of biopsy, the predominant clinical symptoms and signs, and the clinical course. It is likely that, in a number of undiagnosed patients, DM2 is the underlying disorder. With a better understanding of the histopathological pattern in DM2, biopsies from patients with undiagnosed neuromuscular disorders can now be reevaluated.

Myotonic dystrophy type 2

Myotonic dystrophy type 2 (DM2) is a clinically but not genetically heterogeneous, multisystem disorder, that is clinically similar to, but distinct from myotonic dystrophy type 1 (DM1). Initially, different phenotypes of DM2 were described by Ricker (proximal myotonic myopathy, PROMM), Ranum (myotonic dystrophy 2, DM2) and Udd (proximal myotonic dystrophy, PDM). Clinical features these three phenotypes had in common were diffuse, proximal or distal weakness, wasting, myotonia, cataract, cerebral, endocrine and cardiac abnormalities. Initially, the clinical differences between DM1 and PROMM seemed unmistakable, but meanwhile it has become apparent that the clinical differences between these entities are blurring. In 1999, Day et al., Meola et al. and Ricker et al. mapped the mutated gene of all three phenotypes to chromosome 3q. In 2001, the three different phenotypes were found to rely on the same mutation in the ZNF9 gene on chromosome 3q21.3. Although DM2 may be clinically heterogeneous, it is by result of a mutation in a single gene. The mutation responsible for DM2 is a CCTG-repeat expansion of 75-11 000 repeats in intron 1 of the ZNF9 gene on chromosome 3q21.3. Because of the clinical heterogeneity, the diagnosis of DM2 should rely on DNA analysis alone.

Idiopathic painful sensory neuropathy

Unexplained painful burning feet are common complaints among the elderly. Conventional elettrodiagnostic testing may be normal or only minimally abnormal and the lack of a universally accepted diagnostic test for small fiber dysfunction has posed a significant impediment to evaluation of these patients. The increasing application of newer diagnostic techniques, including quantitative sensory testing, tests of sudomotor function, and skin biopsy for intrnepidermal nerve fiber quantification, has permitted recognition and characterization of the idiopathic painful sensory neuropathies This article reviews the clinical features, evaluation, and management of this syndrome.

Clinical and genetic heterogeneity in myotonic dystrophies

This review of myotonic dystrophies primarily concentrates on the clinical and genetic findings that can distinguish a novel form of myotonic dystrophy, myotonic dystrophy type 2 (DM2); proximal myotonic myopathy (PROMM); and proximal myotonic dystrophy (PDM) from myotonic dystrophy type 1 (DM1). The multisystemic nature of these disorders leads to a spectrum of symptoms and signs. Careful clinical evaluation of patients with DM2/PROMM shows that the similarities among the multisystemic myotonic disorders outweigh the differences. An important point in the comparison of the phenotypes of DM1 and DM2/PROMM is that no severe congenital type of DM2/PROMM has yet been described. Genetic linkage analyses show that myotonic dystrophies can be divided into three types: the conventional Steinert type linked to chromosome 19q13.3 (DM1); DM2/PROMM and PDM linked to chromosome 3q21.3; and families not linked to either chromosomal site. Although the diagnosis may be clinically suspected, it depends on DNA analysis.

Myotonic dystrophies

This review demonstrates genetic and phenotypic heterogeneity in all of the multisystemic myotonic disorders collectively called 'myotonic dystrophies' according to the new nomenclature: myotonic dystrophy type 1, myotonic dystrophy type 2, proximal myotonic myopathy and proximal myotonic dystrophy. Only two loci have so far been assigned (19q 13.3 in myotonic dystrophy type 1, and 3q 21.3 in myotonic dystrophy type 2). Although the diagnosis of these disorders may be suspected clinically, it needs to be confirmed by DNA analysis.

Proximal myotonic myopathy: clinical and molecular investigation of a Norwegian family with PROMM

Proximal myotonic myopathy (PROMM) was first described in 1994 as a multisystem disorder with similarity to myotonic dystrophy (DM), but without the abnormal (CTG)n expansion in the DM protein kinase (DMPK) gene. The inheritance is autosomal dominant and the clinical features include myotonia, proximal muscle weakness and cataract. Linkage analysis in nine German PROMM families has indicated the possibility of linkage to DM2 locus on chromosome 3. We report a Norwegian PROMM family in which the proband was clinically diagnosed as DM but without the (CTG)n expansion. Using an intragenic marker we showed that the DMPK gene did not segregate with the disease in this family. All family members are heterozygous for the R894X mutation in CLCN1 gene. Linkage analysis could not be performed, but haplotyping probably excludes the DM2 locus as the disease locus in this family. The present family emphasises that myalgia is a prominent symptom in PROMM and the clinical differences may be explained by genetic heterogeneity. This family will be reinvestigated along with the identification of candidate genes or regions in larger PROMM families.

Proximal myotonic myopathy (PROMM) presenting as myotonia during pregnancy

Proximal myotonic myopathy is a recently described autosomal dominant condition characterized by proximal myopathy, cataracts, intermittent myotonia, and myalgia. We report a further family with this condition. The proband and her two sisters presented with myotonia during pregnancy which resolved after each delivery. Two sisters experienced myalgia between each pregnancy. This relationship between pregnancy and symptom exacerbation suggests an intriguing hormonal influence in PROMM.