Search

Charcot‐Marie‐Tooth (CMT) diseases are a heterogeneous group of genetic peripheral neuropathies caused by mutations in a variety of genes, which are involved in the development and maintenance of peripheral nerves. Myelin protein zero (MPZ) is expressed by Schwann cells, and MPZ mutations can lead to primarily demyelinating polyneuropathies including CMT type 1B. Different mutations demonstrate various forms of disease pathomechanisms, which may be beneficial in understanding the disease cellular pathology. Our molecular dynamics simulation study on the possible impacts of I30T mutation on the MPZ protein structure suggested a higher hydrophobicity and thus lower stability in the membranous structures. A study was also conducted to predict native/mutant MPZ interactions. To validate the results of the simulation study, the native and mutant forms of the MPZ protein were separately expressed in a cellular model, and the protein trafficking was chased down in a time course pattern. In vitro studies provided more evidence on the instability of the MPZ protein due to the mutation. In this study, qualitative and quantitative approaches were adopted to confirm the instability of mutant MPZ in cellular membranes. Highlights: The substitution of 30th Ile by Thr affects interacting properties of the Ig‐like domain of MPZ.The I30T mutation increases the solubility of the extracellular domain of MPZ.Cellular model experiments demonstrated the lower stability of mutant MPZ in the cell membrane. [ABSTRACT FROM AUTHOR]

Congenital myasthenic syndromes (CMSs) are a heterogeneous group of genetic disorders affecting neuromuscular transmission. The agrin/muscle-specific kinase (MuSK) pathway is critical for proper development and maintenance of the neuromuscular junction (NMJ). We report here an Iranian patient in whom CMS was diagnosed since he presented with congenital and fluctuating bilateral symmetric ptosis, upward gaze palsy and slowly progressive muscle weakness leading to loss of ambulation. Genetic analysis of the patient revealed a homozygous missense mutation c.2503A>G in the coding sequence of MUSK leading to the p.Met835Val substitution. The mutation was inherited from the two parents who were heterozygous according to the notion of consanguinity. Immunocytochemical and electron microscopy studies of biopsied deltoid muscle showed dramatic changes in pre- and post-synaptic elements of the NMJs. These changes induced a process of denervation/reinnervation in native NMJs and the formation, by an adaptive mechanism, of newly formed and ectopic NMJs. Aberrant axonal outgrowth, decreased nerve terminal ramification and nodal axonal sprouting were also noted. In vivo electroporation of the mutated MuSK in a mouse model showed disorganized NMJs and aberrant axonal growth reproducing a phenotype similar to that observed in the patient's biopsy specimen. In vitro experiments showed that the mutation alters agrin-dependent acetylcholine receptor aggregation, causes a constitutive activation of MuSK and a decrease in its agrin- and Dok-7-dependent phosphorylation. [ABSTRACT FROM AUTHOR]

Background: Wilson’s disease (WD) is a treatable autosomal recessive metabolic disorder which could lead to protean hepatic or neurologic manifestations. WD could mimic many neurologic disorders and is often diagnosed with a long delay. This study describes central nervous system manifestations of a group of Iranian patients with neurologic WD. Methods: Data from case records of patients with neurologic WD presenting at a referral university hospital and a private clinic in Tehran from 1984 to 2004 were analyzed. Results: Fifty patients from 44 unrelated families with WD were identified, whose mean duration of follow-up was 51.8 (±58.5) months. The median age of onset of neurologic symptoms in 37 patients with primary neurologic or simultaneous hepatic-neurologic presentation was 16 (10–38) years, whereas in 13 patients with prior hepatic damage, this was 18.5 (11–34) years. The 6 most common manifestations were dysarthria (80%), drooling (48%), tremor in limbs (44%), abnormal gait (44%), psychiatric and/or sleep symptoms (44%), and dystonia in limbs (42%). Conclusion: Neurologic WD has heterogeneous manifestations and should be considered in young patients presenting with dysarthria, drooling, any kind of movement disorders or psychiatric symptoms. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Introduction: Myasthenia gravis (MG) is an autoimmune disease that affects the neuromuscular junction. MG patients may present de novo with primary otolaryngology complaints, including swallowing dysfunction. This study describes a range of unique presentations and rare diagnostic serologies, which have not previously been fully described., Methods: A retrospective review was performed of all patients presenting with primary symptom of dysphagia and subsequently diagnosed with MG. Data collected included demographics, clinical presentation, swallow studies, serology, imaging, treatment, and response., Results: Five patients met the inclusion criteria. Four endorsed dysphagia as primary complaint and one endorsed dysphagia and dysphonia. All patients underwent in-office swallow evaluations that showed vallecular or pyriform sinus residue. Three patients completed modified barium swallow studies that showed pharyngeal weakness and epiglottic dysfunction in all, and upper esophageal sphincter dysfunction in two. One patient with additional symptom of dyspnea was admitted and found to be in myasthenic crisis. Upon serologic evaluation, three patients were positive for acetylcholine receptor (AChR) antibodies only, one for muscle-specific-kinase (MuSK) antibodies only, and one for low density lipoprotein receptor-related protein 4 (LRP4) antibodies only. All patients received neurology evaluation and were treated with steroids, pyridostigmine, plasma exchange, or rituximab. In three patients with over 1 year follow-up, symptoms were significantly improved or resolved., Conclusion: MG is an important differential diagnosis in patients with unexplained pharyngeal dysphagia. While workup can include AChR antibody screening, in seronegative patients with persistent symptoms, additional testing for MuSK and LRP4 may lead to diagnosis and effective treatment., Level of Evidence: Level 4 Laryngoscope, 2024., (© 2024 The American Laryngological, Rhinological and Otological Society, Inc.)