Distal Myopathies: Case Studies.

About 15% of myopathies present with distal weakness. Lack of sensory deficit, and preservation of sensory responses and deep tendon reflexes, favors a myopathic cause for distal weakness. Electromyogram confirms this diagnosis. Profuse spontaneous discharges are common in inflammatory, metabolic, and myofibrillar myopathy (MFM). If the clinical picture indicates a specific disease such as facioscapulohumeral muscular dystrophy (FSHD), genetic testing provides the quickest diagnosis. Otherwise, muscle biopsy can distinguish specific features. The common causes of myopathic distal weakness are FSHD, myotonic dystrophy, and inclusion body myositis. Other causes include MFM, distal muscular dystrophies, metabolic myopathies, and congenital myopathies.

Shaibani A 《-》

Distal Myopathies.

Felice KJ 《-》

The first Italian patient with oculopharyngodistal myopathy: case report and considerations on differential diagnosis.

Oculopharyngodistal myopathy is a clinicopathologically distinct muscular disease. The underlying genetic defect has not been identified. We report here a 43-year old woman with asymmetric bilateral ptosis, dysphonia, swallowing difficulties, and weakness of the distal leg muscles. Serum creatine kinase was moderately increased. Electromyography revealed myopathic changes and myotonic discharges. Both cardiologic and pneumologic evaluation did not reveal abnormalities. Muscle computed tomography images showed adipose tissue replacement of abdominis rectus, lateral vastus, adductor magnus, and both the posterior and anterior compartment muscles below the knee, with prevalent involvement of medial gastrocnemius muscle. Muscle biopsy uncovered changes in fiber size and the presence of atrophic fibers with rimmed vacuoles of varying diameter, and core-like structures in type I fibers. Diagnosis was performed according to clinical and histopathologic findings, which were fully consistent with the other reported patients, and on the genetic exclusion of similar conditions such as oculopharyngeal muscular dystrophy, myotonic dystrophy type 1 and multi-minicore disease associated to RYR1 mutations. Differential diagnosis with mitochondrial myopathies, facioscapulohumeral muscular dystrophy and distal myopathies was also considered. This is the first Italian case of oculopharyngodistal myopathy, further suggesting the worldwide distribution of this rare neuromuscular disorder.

Mignarri A ，Carluccio MA ，Malandrini A ，Sicurelli F ，Galli L ，Mazzei MA ，Federico A ，Orrico A ，Dotti MT ... -  《-》

Myofibrillar and distal myopathies.

Distal myopathies and myofibrillar myopathies are both rare subcategories of muscle diseases. Myofibrillar myopathies are genetically heterogeneous group of diseases characterized by distinctive histopathology of abnormal protein aggregations and myofibrillar disintegration. All genes causing myofibrillar myopathy encode proteins that either reside in or associate with the Z-disc. Distal myopathies are also genetically heterogeneous muscular dystrophies in which muscle weakness presents distally in the feet and/or hands. A subgroup of distal myopathies, desminopathy, distal myotilinopathy, ZASPopathy and alpha-B crystallin-mutated distal myopathy, belong to myofibrillar myopathies and show similar pathological changes in muscle biopsies. Common features of these diseases are dominant inheritance and adult-onset of symptoms starting in the feet and slowly progressing to encompass other muscle groups. Cardiomyopathy is not a common feature in distal MFM myopathies.

Palmio J ，Udd B 《REVUE NEUROLOGIQUE》

Panorama of the distal myopathies.

Distal myopathies are genetic primary muscle disorders with a prominent weakness at onset in hands and/or feet. The age of onset (from early childhood to adulthood), the distribution of muscle weakness (upper versus lower limbs) and the histological findings (ranging from nonspecific myopathic changes to myofibrillar disarrays and rimmed vacuoles) are extremely variable. However, despite being characterized by a wide clinical and genetic heterogeneity, the distal myopathies are a category of muscular dystrophies: genetic diseases with progressive loss of muscle fibers. Myopathic congenital arthrogryposis is also a form of distal myopathy usually caused by focal amyoplasia. Massive parallel sequencing has further expanded the long list of genes associated with a distal myopathy, and contributed identifying as distal myopathy-causative rare variants in genes more often related with other skeletal or cardiac muscle diseases. Currently, almost 20 genes (ACTN2, CAV3, CRYAB, DNAJB6, DNM2, FLNC, HNRNPA1, HSPB8, KHLH9, LDB3, MATR3, MB, MYOT, PLIN4, TIA1, VCP, NOTCH2NLC, LRP12, GIPS1) have been associated with an autosomal dominant form of distal myopathy. Pathogenic changes in four genes (ADSSL, ANO5, DYSF, GNE) cause an autosomal recessive form; and disease-causing variants in five genes (DES, MYH7, NEB, RYR1 and TTN) result either in a dominant or in a recessive distal myopathy. Finally, a digenic mechanism, underlying a Welander-like form of distal myopathy, has been recently elucidated. Rare pathogenic mutations in SQSTM1, previously identified with a bone disease (Paget disease), unexpectedly cause a distal myopathy when combined with a common polymorphism in TIA1. The present review aims at describing the genetic basis of distal myopathy and at summarizing the clinical features of the different forms described so far.

Savarese M ，Sarparanta J ，Vihola A ，Jonson PH ，Johari M ，Rusanen S ，Hackman P ，Udd B ... -  《-》