Danon disease is an X-linked dominant multisystem disorder affecting predominantly cardiac and skeletal muscles.

DMRV is allelic to HIBM. Various mutations are associated with DMRV in Japan. The loss-of-function mutations in the GNE gene appear to cause DMRV/HIBM.

Primary collagen VI deficiency is the second most common CMD after Fukuyama type CMD in Japan. Dominant mutations located in the N-terminal side from the cysteine residue in the THD of COL6A1, COL6A2, and COL6A3 are closely associated with SSCD.

and the OPDM_LRP12 Study Group IMPORTANCE Repeat expansion of CGG in LRP12 has been identified as the causative variation of oculopharyngodistal myopathy (OPDM). However, to our knowledge, the clinicopathologic features of OPDM with CGG repeat expansion in LRP12 (hereafter referred to as OPDM_LRP12) remain unknown.OBJECTIVE To identify and characterize the clinicopathologic features of patients with OPDM_LRP12. DESIGN, SETTING, AND PARTICIPANTSThis case series included 208 patients with a clinical or clinicopathologic diagnosis of oculopharyngeal muscular dystrophy (OPDM) from January 1, 1978, to December 31, 2020. Patients with GCN repeat expansions in PABPN1 were excluded from the study. Repeat expansions of CGG in LRP12 were screened by repeat primed polymerase chain reaction and/or Southern blot.MAIN OUTCOMES AND MEASURES Clinical information, muscle imaging data obtained by either computed tomography or magnetic resonance imaging, and muscle pathologic characteristics.RESULTS Sixty-five Japanese patients with OPDM (40 men [62%]; mean [SD] age at onset, 41.0 [10.1] years) from 59 families with CGG repeat expansions in LRP12 were identified. This represents the most common OPDM subtype among all patients in Japan with genetically diagnosed OPDM. The expansions ranged from 85 to 289 repeats. A negative correlation was observed between the repeat size and the age at onset (r 2 = 0.188, P = .001). The most common initial symptoms were ptosis and muscle weakness, present in 24 patients (37%). Limb muscle weakness was predominantly distal in 53 of 64 patients (83%), but 2 of 64 patients (3%) had predominantly proximal muscle weakness. Ptosis was observed in 62 of 64 patients (97%), and dysphagia or dysarthria was observed in 63 of 64 patients (98%). A total of 21 of 64 patients (33%) had asymmetric muscle weakness. Aspiration pneumonia was seen in 11 of 64 patients (17%), and 5 of 64 patients (8%) required mechanical ventilation. Seven of 64 patients (11%) developed cardiac abnormalities, and 5 of 64 patients (8%) developed neurologic abnormalities. Asymmetric muscle involvement was detected on computed tomography scans in 6 of 27 patients (22%) and on magnetic resonance imaging scans in 4 of 15 patients (27%), with the soleus and the medial head of the gastrocnemius being the worst affected. All 42 muscle biopsy samples showed rimmed vacuoles. Intranuclear tubulofilamentous inclusions were observed in only 1 of 5 patients. CONCLUSIONS AND RELEVANCEThis study suggests that OPDM_LRP12 is the most frequent OPDM subtype in Japan and is characterized by oculopharyngeal weakness, distal myopathy that especially affects the soleus and gastrocnemius muscles, and rimmed vacuoles in muscle biopsy.

Among the autophagic vacuolar myopathies (AVMs), a subgroup is characterized pathologically by unusual autophagic vacuoles with sarcolemmal features (AVSF) and includes Danon disease and X-linked myopathy with excessive autophagy. The diagnostic importance and detailed morphologic features of AVSF in different AVMs have not been well established, and the mechanism of AVSF formation is not known. To address these issues, we have performed detailed histologic studies of myopathies with AVSF and other AVMs. In Danon disease and related AVMs, at the light microscopic level, autophagic vacuoles appeared to be accumulations of lysosomes, which, by electron microscopy consisted of clusters of autophagic vacuoles, indicative of autolysosomes. Some autolysosomes were surrounded by membranes with sarcolemmal proteins, acetylcholinesterase activity, and basal lamina. In Danon disease, the number of fibers with AVSF increased linearly with age while the number with autolysosomal accumulations decreased slightly, suggesting that AVSF are produced secondarily in response to autolysosomes. Most of the AVSF form enclosed spaces, indicating that the vacuolar membranes may be formed in situ rather than through sarcolemmal indentation. This unique intracytoplasmic membrane structure was not found in other AVMs. In conclusion, AVSF with acetylcholinesterase activity are autolysosomes surrounded by secondarily generated intracytoplasmic sarcolemma-like structure and delineates a subgroup of AVMs.

Our cell-based assay is useful for anti-cN1A autoantibodies detection. Patients with anti-cN1A autoantibodies demonstrated unique clinicopathological features. In vitro and in vivo passive immunization model results suggest that anti-cN1A autoantibodies may affect protein degradation in myofibers. Ann Neurol 2017;81:512-525.

Features of tumefactive demyelinating lesion (TDL) on magnetic resonance imaging (MRI)can facilitate the differential diagnosis of TDL and neoplastic lesions, but vary considerably among patients. The larger TDL grows, the more difficult it becomes to differentiate TDL from neoplastic lesions. The purpose of this study was to elucidate typical MRI features in 12 patients with large TDL (>30 mm in diameter). METHODSWe identified 12 patients with large TDL (six men, six women; age range 17-64 years, median age 27 years) and studied the clinical histories and the results of laboratory and various radiological studies in these patients. All cases of clinically definite multiple sclerosis were diagnosed in accordance with McDonald's revised criteria. RESULTS Common MRI features of large TDLs included variable degrees of mass effect (71%) and edema (100%), a T2 hypointense rim (79%), venular enhancement (57%), and peripheral restriction on diffusion-weighted images (50%). Ring enhancement (38%), open-ring enhancement (31%), or decreased N-acetylaspartate ratios on magnetic resonance spectroscopy (22%) were less frequently observed. Brain angiography demonstrated venous dilatations on and around the TDL. CONCLUSIONSThe diagnosis of large TDL is challenging. Our findings suggest that multiple venous dilatations on and around TDLs on angiography can facilitate diagnosis.

The authors identified eight patients with Ullrich disease in whom collagen VI was present in the interstitium but was absent from the sarcolemma. By electron microscopy, collagen VI in the interstitium was never linked to the basal lamina. These findings suggest that in these patients it is not the total absence of collagen VI from the muscle but the failure of collagen VI to anchor the basal lamina to the interstitium that is the cause of Ullrich disease. Only one of the patients had a mutation in the collagen VI gene, suggesting that the primary abnormality in most of the patients involved some other molecules.