Citations

ABSTRACTIntroduction: Decremental responses in repetitive nerve stimulation have been reported in a few hereditary myopathies. We examined the frequency of decrement in a cohort of myopathy patients. Methods: We reviewed all patients referred for myopathy who underwent repetitive nerve stimulation between January 2007 and May 2017. We included patients with decrement (>10%) and either a pathological or molecular diagnosis of myopathy. Results: Among 157 patients with myopathies, 4 patients had decrement (2 hydroxychloroquine‐associated vacuolar myopathy, 1 centronuclear myopathy, and 1 distal myopathy). One hydroxychloroquine‐associated vacuolar myopathy patient also had inflammatory myopathy. Pyridostigmine improved weakness in the centronuclear myopathy patient, but not in the distal myopathy patient. No patient with an acquired myopathy received pyridostigmine. Conclusions: Despite the rare occurrence of decrement in myopathy, its presence may urge consideration of pharmacological intervention. Muscle Nerve 59:475–478, 2019

A 70-year-old female presented with a three-year history of evolving macroglossia causing dysphagia and dysarthria, with proximal muscle weakness. Given the classic physical finding of macroglossia, the patient underwent extensive evaluation for amyloidosis which proved to be negative apart from a bone marrow biopsy which stained positive for transthyretin without amino acid sequence abnormality, thus giving wild-type transthyretin amyloidosis. Since the wild-type transthyretin amyloidosis could not entirely explain her clinical presentation and evaluation, further studies were conducted in a sequential manner, thus leading to a diagnosis of Pompe disease explaining her presenting signs and symptoms including her macroglossia. Through this fascinating case, we attempt to highlight the approach for the diagnoses of two rare diseases in a patient by emphasizing the importance of having a broad differential diagnosis when presented with findings which may have been thought as pathognomonic for certain diseases.

ABSTRACT Introduction: Recessive mutations in the anoctamin‐5‐encoding gene (ANO5) cause muscular dystrophy of various phenotypes. Intramuscular interstitial amyloid deposits were detected in a few patients with anoctaminopathy‐5, some with cardiac involvement. The frequency of amyloid deposition in anoctaminopathy‐5 and its impact on phenotype are unknown. Methods: We retrospectively identified patients with genetically proven anoctaminopathy‐5 who had undergone muscle biopsy and reviewed their clinical and laboratory data. Results: Eight of 15 patients with anoctaminopathy‐5 had intramuscular interstitial amyloid deposits. The median age at onset of weakness was 40 and 45 years in the amyloidosis and nonamyloidosis groups, respectively. Mutations occurred throughout the entire gene in the amyloidosis group. Atrial arrhythmia was noted in 4 patients with amyloidosis and in 4 patients without amyloidosis. The latter group also had premature ventricular contractions. One nonamyloidosis patient had septal hypokinesia. Discussion: Intramuscular amyloidosis occurred in 53% of patients with anoctaminopathy‐5 who underwent muscle biopsy and had no impact on the phenotype. Muscle Nerve 59:133–137, 2019

ABSTRACTDistal myopathies are a group of rare muscle diseases characterized by distal weakness at onset. Although acquired myopathies can occasionally present with distal weakness, the majority of distal myopathies have a genetic etiology. Their age of onset varies from early‐childhood to late‐adulthood while the predominant muscle weakness can affect calf, ankle dorsiflexor, or distal upper limb muscles. A spectrum of muscle pathological changes, varying from nonspecific myopathic changes to rimmed vacuoles to myofibrillar pathology to nuclei centralization, have been noted. Likewise, the underlying molecular defect is heterogeneous. In addition, there is emerging evidence that distal myopathies can result from defective proteins encoded by genes causative of neurogenic disorders, be manifestation of multisystem proteinopathies or the result of the altered interplay between different genes. In this review, we provide an overview on the clinical, electrophysiological, pathological, and molecular aspects of distal myopathies, focusing on the most recent developments in the field. Muscle Nerve 59:283–294, 2019