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A precise understanding of the neural substrates underlying tactually-related cognitive impairments such as bilateral tactile agnosia, bilateral agraphesthesia, kinesthetic alexia and kinesthetic reading difficulty is currently incomplete. In particular, recent data have implicated a role for the lateral occipital tactile visual region, or LOtv, in tactile object naming (Amedi et al. Cerebral Cortex 2002). Thus, this study set out to examine the degree to which the LOtv may be involved in tactually-related cognitive impairments by examining two unique cases.To assess whether LOtv or the visual word form area (VWFA) is involved in tactually-related cognitive impairments, the average activation point of LOtv and that of VWFA were placed on the single-photon emission computed tomography (SPECT) cerebral blood flow images of two patients: one with bilateral associative tactile agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading, and the other with kinesthetic reading difficulty.The average LOtv coordinate was involved in the area of hypoperfusion in both patients, whereas that of VWFA was not included in any of the hypoperfused areas.The results support the view that interruption of LOtv or disconnection to LOtv and to VWFA may cause these tactually-related cognitive impairments. Further, bilateral associative tactile agnosia and bilateral agraphesthesia are attributable toward the damage of the occipital lobe, whereas unilateral or predominantly one-sided associative tactile agnosia and agraphesthesia are attributable toward the damage of the parietal lobe.

We report a patient with asymmetric Bálint's syndrome (predominantly right-sided oculomotor apraxia and simultanagnosia and optic ataxia for the right hemispace), and multimodal agnosia (apperceptive visual agnosia and bilateral associative tactile agnosia) with accompanying right hemianopia, bilateral agraphesthesia, hemispatial neglect, global alexia with unavailable kinesthetic reading, and lexical agraphia for kanji (Japanese morphograms), after hemorrhage in the left parieto-occipito-temporal area. The coexistence of tactile agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading suggests that tactile-kinesthetic information can be interrupted because of damage to the fiber connection from the parietal lobe to the occipito-temporal area, leading to these tactually related cognitive impairments.

We report a patient with alexia with agraphia accompanied by letter-by-letter reading after hemorrhage in the left middle and inferior occipital gyri that spared the angular gyrus and the fusiform gyrus. Kanji (Japanese morphograms) and kana (Japanese phonetic writing) reading and writing tests revealed that alexia with agraphia was characterized by kana-predominant alexia and kanji-predominant agraphia. This type of "dorsal" letter-by-letter reading is discernable from conventional ventral type letter-by-letter reading that is observed in pure alexia in that (1) kinesthetic reading is less effective, (2) kana or literal agraphia coexists, and (3) fundamental visual discrimination is nearly normal.

Wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) syndrome has previously been reported in only 2 patients with progressive supranuclear palsy (PSP). Herein, we report a third case of WEBINO syndrome with PSP. The patient was an 81-year-old man who had experienced gradually increasing gait disturbance and occasional falls since the age of 78 years. At 80 years of age, he presented with cognitive impairment, parkinsonism, and oculomotor abnormalities. The oculomotor abnormalities consisted of vertical gaze palsy and loss of eye convergence. Brain magnetic resonance imaging demonstrated marked atrophy of the midbrain. He was diagnosed with PSP. At the age of 81 years, he presented with alternating extropia in his forward gaze and adduction paresis and outward nystagmus of the abducted eye in his horizontal gaze, both of which were compatible with WEBINO syndrome. Previously, we reported the first case of PSP with WEBINO syndrome, and another group recently reported a second case. In light of the previous cases and the present case, WEBINO syndrome in PSP should not be considered extremely rare. Furthermore, WEBINO syndrome has not been reported in other neurodegenerative disorders, which suggests that it might be a useful and specific diagnostic finding in PSP.

Miliary brain metastasis is a rare type of brain metastasis, in which carcinoma cells disseminate to numerous foci confined to Virchow-Robin/subpial spaces. Symptoms usually progress within several months, and magnetic resonance imaging (MRI) shows multiple small contrast-enhancing lesions. We report an autopsy case of a patient who rapidly deteriorated within a week due to miliary brain metastasis after epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) discontinuation, without contrast-enhancing lesions on MRI. A 74-year-old woman was diagnosed with stage IV lung adenocarcinoma with EGFR L868R mutation 2 years before presentation. Gefitinib, an EGFR-TKI was started. After 7 months, multiple new punctate contrast-enhancing lesions in the cerebral cortex appeared. After switching to another EGFR-TKI, erlotinib, these lesions disappeared. One year later, erlotinib was discontinued because of disease progression in the lung and docetaxel was initiated. Sixteen days later, cognitive decline appeared which rapidly progressed to bedridden state in 4 days. MRI showed multiple cortical small fluid-attenuated inversion recovery high intensity lesions which lacked contrast enhancement. The patient exhibited a state of akinetic mutism within a few days, and died 52 days after the appearance of neurological symptoms. The rapid progression indicated disease flare after EGFR-TKI discontinuation. Autopsy revealed numerous foci of metastasis in the cerebral cortex, basal ganglia, thalamus, and cerebellum, in which cancer cells were mostly confined to the Virchow-Robin/subpial spaces. These pathological findings were compatible with previous reports of miliary brain metastasis. Recent reports suggest that early disseminated cancer cells can survive for a long time and even remain after chemotherapy in supportive niches, and Virchow-Robin spaces are the niches in the brain. Our case suggests that these cancer cells may rapidly proliferate as a withdrawal burst after discontinuation of molecular targeted drugs, and show pathological findings of miliary brain metastasis.

Objective: The aim of this study was to investigate the impact of the coronavirus disease 2019 (COVID-19) pandemic on neurology in Japan, by analyzing data on the number of neurological patients at our hospital in Tokyo.Material and Methods: We counted the number of inpatients and outpatients per month; from January 2018 to September 2020. We defined the data from April 2020 to May 2020, as the first wave of the COVID-19 pandemic, and that from July 2020 to September 2020, as the second wave. The data from each wave were compared to those in the same period within the previous 2 years. We also analyzed other data; including, inpatients with stroke, outpatients with Parkinson’s disease, and outpatients with epilepsy.Results: In the first wave, the overall number of inpatients and outpatients greatly decreased; however, the number of inpatients with stroke increased. The ratio of outpatients with Parkinson’s disease, or outpatients with epilepsy to total outpatients also increased. In the second wave, the overall number of inpatients markedly increased, while that of outpatients slightly decreased.Conclusion: All Japanese general hospitals were greatly affected by the COVID-19 pandemic; especially in the first wave, even if the hospitals did not have in-hospital COVID-19 infection, or were not designated for COVID-19. Three factors; i.e. governmental, hospital, and patient factors, could affect the number of neurological patients during the COVID-19 pandemic. The numerical data reflecting the patients’ behavior might provide suggestions for addressing issues during other pandemics in the future.

We report a patient with alexia with agraphia for kanji after hemorrhage in the left posterior middle temporal gyrus. The results of single-character kanji reading and two-character on- (Chinese-st...

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease with marked variety in its clinical manifestations. While characteristic neuroimaging and skin biopsy findings are important clues to the diagnosis, autopsy studies are still important for confirming the exact disease features. We herein report the case of a patient who received an antemortem diagnosis of familial NIID with dementia-dominant phenotype that was later confirmed by an autopsy. Our report is the first to document a case of autopsy-confirmed NIID involving both cognitive impairment and sensorimotor neuropathy.

We report a patient with phonological agraphia (selective impairment of kana [Japanese phonetic writing] nonwords) and acalculia (mental arithmetic difficulties) with impaired verbal short-term memory after a cerebral hemorrhage in the opercular part of the left precentral gyrus (Brodmann area 6) and the adjacent postcentral gyrus. The patient showed phonemic paragraphia in five-character kana nonword writing, minimal acalculia, and reduced digit and letter span. Mental arithmetic normalized after 8 months and agraphia recovered to the normal range at 1 year after onset, in parallel with an improvement of the auditory letter span score from 4 to 6 over a period of 14 months and in the digit span score from 6 to 7 over 24 months. These results suggest a close relationship between the recovery of agraphia and acalculia and the improvement of verbal short-term memory. The present case also suggests that the opercular part of the precentral gyrus constitutes the phonological route in writing that conveys phonological information of syllable sequences, and its damage causes phonological agraphia and acalculia with reduced verbal short-term memory.

We herein report a 65-year-old man demonstrating dementia with Lewy bodies who first presented with Bálint's syndrome. Two years later, a mild cognitive impairment was noted. From three years after onset, he developed progressive parkinsonism, visual hallucination, and autonomic dysfunction, in line with the deterioration of the cognitive function. Single photon emission computed tomography with a 99mTc-ethylcysteinate dimer performed two years after onset revealed hypoperfusion in the restricted area of the bilateral superior parietal lobule, which extended to the lateral occipital cortices within two years. It is suggested that the pathological process can extend from the parietal to occipital lobes.

Objective: We aimed to analyze the clinical and histopathologic features of cancer-associated myositis (CAM) in relation to anti–transcriptional intermediary factor 1 γ antibody (anti-TIF1-γ-Ab), a marker of cancer association. Methods: We retrospectively studied 349 patients with idiopathic inflammatory myopathies (IIMs), including 284 patients with pretreatment biopsy samples available. For the classification of IIMs, the European Neuromuscular Center criteria were applied. Patients with CAM with (anti-TIF1-γ-Ab[+] CAM) and without anti-TIF1-γ-Ab (anti-TIF1-γ-Ab[−] CAM) were compared with patients with IIM without cancers within and beyond 3 years of myositis diagnosis. Results: Cancer was detected in 75 patients, of whom 36 (48%) were positive for anti-TIF1-γ-Ab. In anti-TIF1-γ-Ab(+) patients with CAM, cancers were detected within 1 year of myositis diagnosis in 35 (97%) and before 1 year of myositis diagnosis in 1. All the anti-TIF1-γ-Ab(+) patients with CAM satisfied the dermatomyositis (DM) criteria, including 2 possible DM sine dermatitis cases, and were characterized histologically by the presence of perifascicular atrophy, vacuolated fibers (VFs), and dense C5b-9 deposits on capillaries (dC5b-9). In contrast, 39 anti-TIF1-γ-Ab(−) patients with CAM were classified into various subgroups, and characterized by a higher frequency of necrotizing autoimmune myopathy (NAM). Notably, all 7 patients with CAM classified into the NAM subgroup were anti-TIF1-γ-Ab(−) and exhibited no dC5b-9 or VFs. Conclusions: CAM includes clinicohistopathologically heterogeneous disease entities. Among CAM entities, anti-TIF1-γ-Ab(+) CAM has characteristically shown a close temporal association with cancer detection and the histopathologic findings of dC5b-9 and VFs, and CAM with NAM is a subset of anti-TIF1-γ-Ab(−) CAM.

Since autonomic dysfunction is closely associated with autoimmune encephalitis (AE), the objective of this study was to determine the autonomic symptoms and the prevalence of anti-α3 subunit of the ganglionic-type nicotinic acetylcholine receptor (gAChRα3) antibodies in the patients with AE. We reviewed the clinical features of 19 AE patients, and specifically analyzed sera for anti-gAChRα3 antibodies using the luciferase immunoprecipitation system (LIPS) assay. Cardiovascular autonomic symptoms were found to be common in patients with AE, and hypersalivation was seen only in patients with NMDAR encephalitis. LIPS detected anti-gAChRα3 antibodies in the sera from patients with AE (5/29, 26%). This study is the first to demonstrate that clinical characteristics including autonomic symptoms of AE patients with seropositivity for gAChR autoantibodies. It will be important to verify the role of gAChR antibodies in autonomic dysfunction and brain symptoms to clarify the pathogenesis of AE.

The kanji and kana (or kanji vs. kana) problem in the Japanese language denotes the dissociation between kanji (morphograms) and kana (phonograms) in reading/comprehension and writing. Since paragraphia of kana in a patient with amyotrophic lateral sclerosis was first reported in 1893, kanji-kana dissociation has been the central topic in Japanese aphasiology. Recent advancements in lesion-to-symptom analyses and functional imaging studies have identified some areas whose damage causes dissociative disturbances of reading or writing between kanji and kana. That is, (1) angular alexia with agraphia causes kanji agraphia; alexia of kana with an angular gyrus lesion is the result of a damage to the middle occipital gyrus; (2) alexia with agraphia for kanji is caused by a posterior inferior temporal cortex (mid-fusiform/inferior temporal gyri; visual word form area) lesion, whereas pure agraphia for kanji is caused by a posterior middle temporal gyrus lesion; and (3) pure alexia, particularly for kanji, results from a mid-fusiform gyrus lesion (Brodmann's Area [BA] 37), whereas pure alexia for kana results from a posterior fusiform/inferior occipital gyri lesion (BA 18/19).

We report a patient with ventral simultanagnosia, prosopagnosia for "unfamiliar faces" (dorsal prosopagnosia), spatial agraphia, and constructional disorder, particularly on the left spatial side, due to a lesion in the right posterior superior and middle temporal gyri and angular gyrus. The patient showed impairment of fundamental visual and visuospatial recognition, such as in object size, configuration, and horizontal point location, which probably underlay the mechanism of simultanagnosia and prosopagnosia. This case also suggests that the coexistence of simultanagnosia and prosopagnosia results from a right hemispheric insult, and damage to the temporoparietal area interrupts the incorporation of spatial information into object recognition. This disconnection of information flow, together with impaired object recognition per se, may impair the parallel processing of multiple objects, leading to object-by-object or part-by-part recognition.

The kanji and kana (or kanji vs. kana) problem in the Japanese language denotes the dissociation between kanji (morphograms) and kana (phonograms) in reading/comprehension and writing. Since paragraphia of kana in a patient with amyotrophic lateral sclerosis was first reported in 1893, kanji-kana dissociation has been the central topic in Japanese aphasiology. Recent advancements in lesion-to-symptom analyses and functional imaging studies have identified some areas whose damage causes dissociative disturbances of reading or writing between kanji and kana. That is, (1) angular alexia with agraphia causes kanji agraphia; alexia of kana with an angular gyrus lesion is the result of a damage to the middle occipital gyrus; (2) alexia with agraphia for kanji is caused by a posterior inferior temporal cortex (mid-fusiform/inferior temporal gyri; visual word form area) lesion, whereas pure agraphia for kanji is caused by a posterior middle temporal gyrus lesion; and (3) pure alexia, particularly for kanji, results from a mid-fusiform gyrus lesion (Brodmann's Area [BA] 37), whereas pure alexia for kana results from a posterior fusiform/inferior occipital gyri lesion (BA 18/19).

Bálint's syndrome involves bilateral damage to the parieto-occipital area. The extent of the effect of unilateral damage on the Bálint's triad (oculomotor apraxia, optic ataxia, and simultanagnosia) remains unknown.We examined a 63-year-old, right-handed woman who developed right hemianopia, oculomotor apraxia, optic ataxia, simultanagnosia, and hemispatial neglect (HSN) for the right after a cerebral infarction, with detailed neuropsychological tests, magnetic resonance imaging, and single photon emission computed tomography (SPECT).Neuropsychological examination showed that oculomotor apraxia, optic ataxia, and simultanagnosia were more pronounced in the right hemi-space, probably due to the limited eye movement in the right visual field, whereas HSN was restricted to the right hemi-space. Diffusion-weighted MR images revealed hyperintensity in the left parieto-temporo-occipital region, and several spotty areas of the bilateral frontal and parietal subcortical regions. SPECT revealed hypoperfusion in the left parieto-occipital region and frontal operculum and small areas of the right superior parietal lobule.The case suggests that asymmetric (more pronounced in the right hemi-space) oculomotor apraxia, optic ataxia, and simultanagnosia occur in an extensive lesion of the left parieto-occipital cortices. Although HSN is not a prerequisite for simultanagnosia, the coexistence of HSN aggravates simultanagnosia in the hemi-space opposite the lesion.

We report a case of Campylobacter fetus (C. fetus) meningitis that manifested a chronic clinical course in an asplenic diabetic patient. The patient had eaten raw beef liver, and after 1 week, he suffered from headache and fever, with repeated remissions and deterioration. Four weeks after onset, neck stiffness was observed, and he was diagnosed with meningitis due to Campylobacter fetus. The cerebrospinal fluid (CSF) sample showed leukocytosis (3760/μl; neutrophils 91 %, lymphocytes 9 %). The infection responded to meropenem and ampicillin. A review of the literature between 1976 and 2013 revealed that C. fetus meningitis in adults is still a rare entity, and about one-third of case reports written in English are from Japan. We specifically reviewed the case reports of C. fetus meningitis in adults written in Japanese between 1979 and 2013 to examine the clinical features and influence of underlying disease, especially diabetes mellitus. Unexpectedly, most patients with C. fetus meningitis manifested a chronic clinical course, and CSF samples showed lymphocyte-predominant leukocytosis in at least 25 out of 43 cases. Antibiotic treatment, especially with carbapenem, was effective, and the overall prognosis of C. fetus meningitis was good, but 3 out of 43 patients had after effects. Two of the patients had diabetes mellitus as an underlying disease.

We report a Japanese-speaking monolingual woman who developed foreign accent syndrome (FAS) following an infarction in the precentral and premotor cortices (Brodmann Area 6) at and around the inferior frontal sulcus. Her speech sounded Chinese or Korean to our bilingual coauthor who speaks Chinese and Japanese. Quantitative acoustic analyses of words and sentences showed that pitch (fundamental frequency variation) and intensity variances appeared lowered and fully voiced glottal pulses were reduced. These findings suggest laryngeal dysfunction that contributes to the unusual speech production in a case of FAS. This may be caused by damage to a restricted area of the motor and premotor cortices that controls laryngeal function.

We report a 45-year-old man with motor axonal Guillain–Barre syndrome who developed left facial nerve palsy, right hypoglossal nerve palsy, and predominantly left-sided upper limb paresis and left lower limb paresis. Blood examination identified immunoglobulin G antibodies against gangliosides GD1a, GD1b and GQ1b, and GD1b/GD1a and GD1b/GT1b complexes. He was treated with intravenous immunoglobulin (400 mg/kg/day for 5 days) twice, and tongue deviation and facial palsy resolved in 3 months. Unilateral or asymmetric involvement of the cranial and limb nerves represent a variant form of axonal Guillain–Barre syndrome.

A 65-year-old woman developed progressive apraxic agraphia, characterized by poorly formed graphemes, a kanji (Japanese morphograms) recall impairment, relatively preserved oral spelling of kanji characters, and incorrect stroke sequences on writing accompanied by micrographia over a 3-year period. She also showed minor degrees of rigidity, limb-kinetic apraxia, and ideomotor apraxia of the left hand. Although asymmetric rigidity and limb-kinetic apraxia strongly suggested corticobasal degeneration, (11)C-Pittsburgh compound B positron emission tomography (PiB-PET) showed the predominantly right-sided accumulation of amyloid β in the cortices and striatum. (18)F-fluoro-deoxy-glucose PET and single photon emission computed tomography with a (99m)Tc-ethylcysteinate dimer (ECD-SPECT) also revealed predominantly right-sided hypometabolism and hypoperfusion in the primary sensorimotor cortex, posterior cingulate gyrus, temporoparietal cortices, frontal cortices, thalamus, and basal ganglia, a pattern characteristic of both corticobasal degeneration and Alzheimer's disease. The findings suggest that progressive apraxic agraphia with micrographia presenting as corticobasal syndrome can show an Alzheimer's disease pathology. It is also suggested that ideomotor apraxia of the left hand can occur without a callosal lesion, and is caused by hypometabolism or hypoperfusion in the right frontal and parietal cortices, as revealed by PET and SPECT.

Objective: To show cancer association is a risk factor other than statin exposure for anti-3-hydroxy-3-methylglutaryl coenzyme A reductase autoantibody-positive (anti-HMGCR Ab+) myopathy. Methods: We analyzed the clinical features and courses of 33 patients (23 female and 10 male) with anti-HMGCR Ab+ myopathy among 621 consecutive patients with idiopathic inflammatory myopathies. Results: Among the 33 patients, 7 (21%) were statin-exposed and 26 were statin-naive. In relation with cancer, there were 12 patients (statin-exposed, n = 4) with cancers detected within 3 years of myopathy diagnosis (cancer association), 3 patients (all statin-naive) with cancers detected more than 3 years before myopathy diagnosis (cancer history), 10 cancer-free patients followed up for more than 3 years (all statin-naive), and 8 patients without cancer detection but followed up for less than 3 years (statin-exposed, n = 3). Therefore, 12 patients with cancer association (36%) formed a larger group than that of 7 statin-exposed patients (21%). Among 12 patients with cancer association, 92% had cancer detection within 1 year of myopathy diagnosis (after 1.3 years in the remaining patient), 83% had advanced cancers, and 75% died of cancers within 2.7 years. Of interest, 1 patient with cancer history had sustained increase in creatine kinase level over 12 years from cancer removal to the development of weakness. Conclusions: Patients with cancer association formed a large group with poor prognosis in our series of patients with anti-HMGCR Ab+ myopathy. The close synchronous occurrence of cancers and myopathies suggested that cancer association is one of the risk factors for developing anti-HMGCR Ab+ myopathy.

We read with great interest the article by Itabashi et al1 recently published in Stroke . Using voxel-based lesion-symptom mapping analysis on magnetic resonance imagings of a large number of patients, the authors clearly demonstrated that a restricted area in the left motor cortex is associated with the presentation of apraxia of speech, notably even with that without aphasia. We have previously reported that lesions in almost the same region in the left motor cortex can cause aphemia, but without overt signs of aphasia, suggesting this motor region to be essential for speech articulation.2 Some authors associated the same region with the foreign accent syndrome. Together, it is plausible that this motor area plays an important role in motor speech production.1 Located …

Proteinase 3 anti-neutrophil cytoplasmic antibody (PR3-ANCA) is reported to be highly specific to vasculitis compared to myeloperoxidase (MPO)-ANCA. We report a case of a 19-year-old woman with chronic inflammatory demyelinating polyneuropathy (CIDP) with high PR3-ANCA positivity. The patient responded well to intravenous immunoglobulin plus oral steroid, and showed no signs of systemic vasculitis during the subsequent 10 months of follow-up. Our present case suggests that CIDP may accompany high PR3-ANCA levels, which should be differentiated from axonal neuropathy due to vasculitis.

Two patients with isolated thalamic agraphia are described. Both showed kanji (Japanese morphograms) agraphia due to impaired character recall, grapheme deformity and micrographia (progressive reduction in character size during writing) after a lesion that involved the ventral lateral and ventroposterolateral nuclei. Single photon emission computed tomography with a (99m)Tc-ethylcysteinate dimer revealed hypoperfusion in the left precentral gyrus (Brodmann Area 6) and anterior supramarginal gyrus in both. Six months later, the extent of blood flow reduction decreased in the supramarginal gyrus in both patients and the precentral gyrus in patient 1. By this time, the writing impairment improved to nearly the normal range. Our study suggests that kanji agraphia (corresponding to lexical agraphia in Western countries) with poor grapheme formation and micrographia arises from a lesion in the ventral lateral and ventroposterolateral nuclei in the left thalamus. The accompaniment of poor grapheme formation and micrographia may reflect disruption of the cortico-subcortical motor circuit involving the putamen, thalamus, premotor cortex and sensorimotor cortex. It is also suggested that multiple cortical sites can be a target for secondary dysfunction that yields agraphia in a thalamic lesion, and that the recovery of reduced cortical blood flow does not always proceed in parallel with that of agraphia.

The author reviews the lesion localization of non-aphasic alexia and agraphia and proposes a new classification of alexia and agraphia on this basis. The newly proposed alexia and agraphia are pure alexia for kana (Japanese phonograms), or more generally pure alexia for letters, caused by a lesion in the posterior occipital area (posterior fusiform/inferior occipital gyri), and pure agraphia for kanji (Japanese morphograms) caused by a lesion in the posterior middle temporal gyrus and also a lesion restricted to the angular gyrus. In addition, the anatomical lesions presumably responsible for the parietal apraxic agraphia, frontal pure agraphia and thalamic agraphia are discussed.

ObjectiveTo provide evidence that idiopathic inflammatory myopathy (IM) with myasthenia gravis (MG) frequently shows thymoma association and polymyositis (PM) pathology and shares clinicopathologic characteristics with IM induced by immune checkpoint inhibitors (ICIs).MethodsWe analyzed the clinicopathologic features of 10 patients with idiopathic IM and MG identified in 970 consecutive patients with biopsy-proven IM.ResultsSeven patients (70%) had thymoma. IM and MG were diagnosed with more than 5-year time difference in 6 thymomatous patients and within 1 year in 1 thymomatous and 3 nonthymomatous patients. Seven thymomatous patients showed rhabdomyolysis-like features with respiratory failure (4/7), dropped head (3/7), cardiac involvement (2/7), and positive anti–acetylcholine receptor (anti-AChR) and anti-titin antibodies (7/7 and 4/6, respectively) but rarely showed ocular symptoms (2/7) or decremental repetitive nerve stimulation (RNS) responses (1/7) at IM diagnosis. Three nonthymomatous patients showed acute cardiorespiratory failure with rhabdomyolysis-like features (1/3), positive anti-AChR and anti-titin antibodies (3/2 and 2/2, respectively), and fluctuating weakness of the skeletal muscle without ocular symptoms (3/3). Muscle pathology showed a PM pathology with infiltration of CD8-positive CD45RA-negative T-lymphocytes (9/9), scattered endomysial programmed cell death 1 (PD-1)–positive cells (9/9), and overexpression of programmed cell death ligand 1 (PD-L1) on the sarcolemma of muscle fibers around the infiltrating PD-1–positive cells (7/9).ConclusionRhabdomyolysis-like features, positive anti-AChR antibody without decremental RNS responses, and PD-L1 overexpression are possible characteristics shared by ICI-induced IM. Frequent thymoma association in patients with idiopathic IM and MG may suggest thymoma-related immunopathogenic mechanisms, including dysregulation of the immune checkpoint pathway.