Serum cytokines profile changes in amyotrophic lateral sclerosis.

Background: Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder, characterized by progressive limb weakness, dysphagia, dysphonia, and respiratory failure due to degeneration of upper and lower motor neurons. The pathogenesis of ALS is still unclear. Neuroinflammation has been found to be involved in its development and progression. Cytokines play a significant role in the inflammatory process. This study aims to identify novel biomarkers that may assist in the diagnosis of ALS. Methods: In Fujian Medical University Union Hospital and Huashan Hospital Fudan University, two independent centers, we prospectively recruited 50 ALS patients, and 41 healthy controls (25 ALS and 26 controls in the first stage and 25 ALS and 15 controls in the validation stage). An 18-plex Luminex kit was used to screen the serum cytokines levels in the first stage. Commercial ELISA kits were used to measure the levels of target cytokines in the validation stage. A single-molecule array HD-X platform was applied to assess the levels of serum neurofilament light chain (NFL). Results: The levels of serum IL-18 were markedly increased in patients with ALS in the first stage (p = 0.016). The ROC curve showed an area under the curve at 0.695 (95% CI 0.50-0.84) in distinguishing ALS patients from healthy controls. The IL-21 was decreased in elderly patients when grouped by 55 years old (the medium age). Furthermore, the IL-5, IL-13, IL-18, and NFL had a positive relationship with the disease progression of ALS. We also found that serum IL-18 was markedly increased in ALS patients in the validation stage (167.67 [148.25-175.59] vs 116.44 [102.43-122.19]pg/ml, p < 0.0015). Conclusion: In this study, we identified systemic cytokine profile changes in the serum of ALS patients, especially the elevated IL-18, as well as the decreased IL-21 in elder patients. These changes in serum cytokine profiles may shed new light on an in-depth understanding of the immunopathogenic characteristics of ALS.

Eomesodermin expression in CD4+T-cells associated with disease progression in amyotrophic lateral sclerosis.

AIM: To clarify the role of Eomesodermin (EOMES) to serve as a disease-relevant biomarker and the intracellular molecules underlying the immunophenotype shifting of CD4+T subsets in amyotrophic lateral sclerosis (ALS). METHODS: The derivation and validation cohorts included a total of 148 ALS patients and 101 healthy controls (HCs). Clinical data and peripheral blood were collected. T-cell subsets and the EOMES expression were quantified using multicolor flow cytometry. Serum neurofilament light chain (NFL) was measured. In 1-year longitudinal follow-ups, the ALSFRS-R scores and primary endpoint events were further recorded in the ALS patients of the validation cohort. RESULTS: In the derivation cohort, the CD4+EOMES+T-cell subsets were significantly increased (p < 0.001). EOMES+ subset was positively correlated with increased serum NFL levels in patients with onset longer than 12 months. In the validation cohort, the elevated CD4+EOMES+T-cell proportions and their association with NFL levels were also identified. The longitudinal study revealed that ALS patients with higher EOMES expression were associated with higher progression rates (p = .010) and worse prognosis (p = .003). CONCLUSIONS: We demonstrated that increased CD4+EOMES+T-cell subsets in ALS were associated with disease progression and poor prognosis. Identifying these associations may contribute to a better understanding of the immunopathological mechanism of ALS.

Safety of COVID-19 vaccine in patients with myasthenia gravis: a self-controlled case series study.

Background: The safety of COVID-19 vaccines has been clarified in clinical trials; however, some immunocompromised patients, such as myasthenia gravis (MG) patients, are still hesitant to receive vaccines. Whether COVID-19 vaccination increases the risk of disease worsening in these patients remains unknown. This study aims to evaluate the risk of disease exacerbation in COVID-19-vaccinated MG patients. Methods: The data in this study were collected from the MG database at Tangdu Hospital, the Fourth Military Medical University, and the Tertiary Referral Diagnostic Center at Huashan Hospital, Fudan University, from 1 April 2022 to 31 October 2022. A self-controlled case series method was applied, and the incidence rate ratios were calculated in the prespecified risk period using conditional Poisson regression. Results: Inactivated COVID-19 vaccines did not increase the risk of disease exacerbation in MG patients with stable disease status. A few patients experienced transient disease worsening, but the symptoms were mild. It is noted that more attention should be paid to thymoma-related MG, especially within 1 week after COVID-19 vaccination. Conclusion: COVID-19 vaccination has no long-term impact on MG relapse.

Serum metabolomic characterization of PLA2G6-associated dystonia-parkinsonism: A case-control biomarker study.

Introduction: Phospholipase A2 Group VI (PLA2G6), encoding calcium-independent phospholipase A2, has been isolated as the gene responsible for an autosomal recessive form of early-onset Parkinson's disease (namely, PARK14). Compared to idiopathic Parkinson's disease (iPD), PARK14 has several atypical clinical features. PARK14 has an earlier age at onset and is more likely to develop levodopa-induced dyskinesia. In iPD, serum metabolomics has observed alterations in several metabolic pathways that are related to disease status and clinical manifestations. This study aims to describe the serum metabolomics features of patients with PARK14. Design: This case-control biomarker study tested nine patients diagnosed with PARK14. Eight age and sex-matched healthy subjects were recruited as controls. To evaluate the influence of single heterozygous mutation, we enrolled eight healthy one-degree family members of patients with PARK14, two patients diagnosed with early-onset Parkinson's disease (EOPD) who had only a single heterozygous PLA2G6 mutation, and one patient with EOPD without any known pathogenic mutation. Methods: The diagnosis of PARK14 was made according to the diagnostic criteria for Parkinson's disease (PD) and confirmed by genetic testing. To study the serum metabolic features, we analyzed participants' serum using UHPLC-QTOF/MS analysis, a well-established technology. Results: We quantified 50 compounds of metabolites from the serum of all the study subjects. Metabolites alterations in serum had good predictive accuracy for PARK14 diagnosis (AUC 0.903) and advanced stage in PARK14 (AUC 0.944). Of the 24 metabolites that changed significantly in patients' serum, eight related to lipid metabolism. Oleic acid and xanthine were associated with MMSE scores. Xanthine, L-histidine, and phenol correlated with UPDRS-III scores. Oleic acid and 1-oleoyl-L-alpha-lysophosphatidic acid could also predict the subclass of the more advanced stage in the PLA2G6 Group in ROC models. Conclusion: The significantly altered metabolites can be used to differentiate PLA2G6 pathogenic mutations and predict disease severity. Patients with PLA2G6 mutations had elevated lipid compounds in C18:1 and C16:0 groups. The alteration of lipid metabolism might be the key intermediate process in PLA2G6-related disease that needs further investigation.

Neurofilament light is a novel biomarker for mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes.

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) is a complicated maternally inherited disorder lacking of sensitive and specific biomarkers. The objective of this study was to investigate the serum neurofilament light chain (NfL) as a novel biomarker of neurological dysfunction in MELAS. Patients with different status of MELAS were enrolled in this study. The Mini-Mental State Examination (MMSE) was given to the participants to evaluate cognition status. Multiple functional MRI was performed on the participants. Blood samples were collected and the serum NfL concentrations were determined by the single-molecule array technology (Simoa). This study enrolled 23 patients with MELAS, 15 people in the acute attack phase of MELAS and 10 people in the remission phase, including 2 patients in both acute attack and remission phase. Sixteen healthy controls (HCs) were also enrolled. Serum NfL level increased significantly in patients with MELAS. Serum NfL level in the acute attack group (146.73 [120.91-411.31] pg/ml, median [IQR]) was higher than in the remission group (40.31 [19.54-151.05] pg/ml, median [IQR]) and HCs group (7.70 [6.13-9.78] pg/ml, median [IQR]) (p < 0.05). The level of NfL in the remission phase group was higher than in HCs group (p < 0.05). A negative correlation was found between the serum NfL level and MMSE (p = 0.006, r = -0.650). The NfL concentration correlated positively with stroke-like lesion volume in the brain (r = 0.740, p < 0.001). Serum NfL may serve as a novel biomarker for the neurological dysfunction in MELAS patients.

Disease Progression in Patients with Parkin-Related Parkinson's Disease in a Longitudinal Cohort.

BACKGROUND: There was a paucity of follow-up studies in the disease progression of early-onset PD patients with Parkin mutations (Parkin-EOPD). Here we conducted a longitudinal study to investigate the progression of motor and cognitive features of Parkin-EOPD patients. METHODS: Genetic analysis was performed via target sequencing and multiplex ligation-dependent probe amplification. Thirty patients carrying homozygous or compound heterozygous Parkin mutations with at least 2 follow-up revisions were investigated as the Parkin-EOPD group. Fifty-two patients with at least 2 follow-up revisions, who did not have any known causative PD mutations, GBA or LRRK2 risk variants, a heterozygous Parkin mutation or 2 Parkin mutations without a segregation test, were defined as the genetically undefined EOPD (GU-EOPD) group. A linear mixed-effect model was implemented to evaluate longitudinal changes in motor symptoms and cognition. RESULTS: At baseline, the Parkin-EOPD group had a lower Unified Parkinson's Disease Rating Scale score (UPDRS-III) (off-medication) than the GU-EOPD group, without significant differences in cognition. A longitudinal study showed the estimated progression rate per year (standard error) of the UPDRS-III score (off-medication) was lower in the Parkin-EOPD group (0.203 [0.3162] points per year) than in the GU-EOPD group (1.056 [0.3001] points per year). The difference in the UPDRS-III score rate between the 2 groups was 0.853 (0.4183) (P = 0.042). The Parkin-EOPD group showed better maintenance of spatial processing ability compared with the GU-EOPD group (P = 0.027). CONCLUSION: Parkin-EOPD patients showed a slower deterioration of motor symptoms and a better spatial processing ability than GU-EOPD patients, which suggests that subtyping according to genetic features can help predict PD progression. © 2020 International Parkinson and Movement Disorder Society.

Propagated α-synucleinopathy recapitulates REM sleep behaviour disorder followed by parkinsonian phenotypes in mice.

Idiopathic rapid eye movement sleep behaviour disorder (RBD) is now recognized as an early manifestation of α-synucleinopathies. Increasing experimental studies demonstrate that manipulative lesion or inactivation of the neurons within the sublaterodorsal tegmental nucleus (also known as the subcoeruleus nucleus in humans) can induce RBD-like behaviours in animals. As current RBD animal models are not established on the basis of α-synucleinopathy, they do not represent the pathological substrate of idiopathic RBD and thus cannot model the phenoconversion to Parkinson's disease. The purpose of this study was therefore to establish an α-synucleinopathy-based RBD animal model with the potential to convert to parkinsonian disorder. To this end, we first determined the functional neuroanatomical location of the sublaterodorsal tegmental nucleus in wild-type C57BL/6J mice and then validated its function by recapitulating RBD-like behaviours based on this determined nucleus. Next, we injected preformed α-synuclein fibrils into the sublaterodorsal tegmental nucleus and performed regular polysomnographic recordings and parkinsonian behavioural and histopathological studies in these mice. As a result, we recapitulated RBD-like behaviours in the mice and further showed that the α-synucleinopathy and neuron degeneration identified within the sublaterodorsal tegmental nucleus acted as the neuropathological substrates. Subsequent parkinsonian behavioural studies indicated that the α-synucleinopathy-based RBD mouse model were not stationary, but could further progress to display parkinsonian locomotor dysfunction, depression-like disorder, olfactory dysfunction and gastrointestinal dysmotility. Corresponding to that, we determined α-synuclein pathology in the substantia nigra pars compacta, olfactory bulb, enteral neuroplexus and dorsal motor nucleus of vagus nerve, which could underlie the parkinsonian manifestations in mice. In conclusion, we established a novel α-synucleinopathy-based RBD mouse model and further demonstrated the phenoconversion of RBD to Parkinson's disease in this animal model.

Quality of Life in Newly Diagnosed Patients With Parkin-Related Parkinson's Disease.

Introduction: Mutations in the Parkin gene are the most common cause of autosomal recessive early-onset Parkinson's disease (PD). However, little is known about the quality of life (QoL) in Parkin-related PD. Here, we investigated the patterns of QoL in newly diagnosed Parkin-related PD patients. Methods: Newly diagnosed PD patients (diagnosis made within 12 months) who had an age of onset (AOO) below 40 and underwent a PD-related genetic testing, were recruited (n = 148). Among them, 24 patients carried bi-allelic variants in Parkin (PD-Parkin) and 24 patients did not have any known causative PD mutations, or risk variants (GU-EOPD). The clinical materials, relevant factors and determinants of QoL were analyzed. Results: PD-Parkin patients had a younger AOO (p = 0.003) and longer disease duration (p = 0.005). After adjustment for AOO and disease duration, more dystonia (p = 0.034), and worse scores of non-motor symptoms including Beck depression inventory (BDI, p = 0.035), Epworth sleepiness scale (ESS, p = 0.044), and subdomains of depression/anxiety (p = 0.015) and sleep disorders (p = 0.005) in Non-motor symptoms questionnaire, were found in PD-Parkin comparing with GU-EOPD. PD-Parkin patients had poorer QoL (adjusted p = 0.045), especially in the mobility (adjusted p = 0.025), emotional well-being (adjusted p = 0.015) and bodily discomfort dimensions (adjusted p = 0.016). BDI scores (p = 0.005) and ESS scores (p = 0.047) were significant determinants of QoL in PD-Parkin. Conclusion: Newly diagnosed PD-Parkin patients showed worse QoL. More depression and excessive daytime sleepiness predicted worse QoL. For clinicians, management of depression and excessive daytime sleepiness is suggested to better improve QoL in patients with Parkin mutations.

Inhibition of ROCK activity regulates the balance of Th1, Th17 and Treg cells in myasthenia gravis.

Aberrant ROCK activation has been found in patients with several autoimmune diseases, but the role of ROCK in myasthenia gravis (MG) has not yet been clearly investigated. Here, we demonstrated that ROCK activity was significantly higher in peripheral blood mononuclear cells (PBMCs) from MG patients. ROCK inhibitor Fasudil down-regulated the proportions of Th1 and Th17 cells in PBMCs of MG patients in vitro. Intraperitoneal injection of Fasudil ameliorated the severity of experimental autoimmune myasthenia gravis (EAMG) rats and restored the balance of Th1/Th2/Th17/Treg subsets. Furthermore, Fasudil inhibited the proliferation of antigen-specific Th1 and Th17 cells, and inhibited CD4 + T cells differentiated into Th1 and Th17 through decreasing phosphorylated Stat1 and Stat3, but promoted Treg cell differentiation through increasing phosphorylated Stat5. We conclude that dysregulated ROCK activity may be involved in the pathogenic immune response of MG and inhibition of ROCK activity might serve as a novel treatment strategy for MG.

Association of the TBK1 mutation p.Ile334Thr with frontotemporal dementia and literature review.

BACKGROUND: The mutation of TANK-binding kinase 1 (TBK1) gene has been regarded as a causative gene of frontotemporal dementia (FTD)-amyotrophic lateral sclerosis (ALS) spectrum disease in recent years. So far, more than 70 TBK1 variants have been identified in patients with FTD-ALS spectrum. METHODS: We reported a Chinese FTD patient carrying TBK1 p.Ile334Thr variant detected by target sequencing and Sanger sequencing. The patient's clinical materials were collected. The transcription and translation levels of TBK1 mutant were investigated in fibroblast by qPCR and western blot. The effects of TBK1 mutant in inflammation pathway and autophagy were detected by luciferase reporter assay and GST pull-down assay. RESULTS: The patient was diagnosed as behavioral variant FTD (bvFTD) and displayed progressively severe cognitive impairment especially in executive function. A pattern of frontotemporal atrophy and hypometabolism was shown through MRI and PET-CT. In vitro functional experiments of TBK1 p.Ile334Thr variant demonstrated reduced transcription and translation levels, decreased kinase activity but maintenance of interaction with optineurin. The variant was classified as likely pathogenic according to American College of Medical Genetics and Genomics guideline. CONCLUSION: We proposed the TBK1 mutation p.Ile334Thr as a likely pathogenic variant in bvFTD which also expanded the clinical spectrum of this variant. It can partially abrogate TBK1 functions and be responsible for FTD-ALS spectrum diseases through neuroinflammatory pathway.

A homozygous missense variant in HSD17B4 identified in a consanguineous Chinese Han family with type II Perrault syndrome.

BACKGROUND: Perrault syndrome is a rare multisystem disorder that manifests with sensorineural hearing loss in both sexes, primary ovarian insufficiency in females and neurological features. The syndrome is heterogeneous both genetically and phenotypically. CASE PRESENTATION: We reported a consanguineous family (two affected sisters) with Perrault syndrome. The proband had the characteristics of Perrault syndrome: ovarian dysgenesis, bilateral hearing loss and obvious neurological signs. Target genetic sequencing and triplet repeat primed PCR (TP-PCR) plus capillary electrophoresis was conducted to detect causative mutations in the proband. The detected variant was further confirmed in the proband and tested in other family members by Sanger sequencing. Both the proband and her sister were found homozygous for the novel variant HSD17B4 c.298G > T (p.A100S) with their parents heterozygous. Detected by western blot, the protein expression of HSD17B4 mutant was much lower than that of the wild type in SH-SY5Y cells transfected by HSD17B4 wild type or mutant plasmid, which indicated the pathogenicity of the HSD17B4 mutation. CONCLUSIONS: Our findings supported that HSD17B4 was one of the genes contributing to Perrault syndrome with the likely pathogenic variant c.298G > T (p.A100S). Special manifestations of cerebellar impairment were found in cases caused by HSD17B4 mutations. Besides, attention should be paid to distinguish Perrault syndrome from D-bifunctional protein deficiency and hereditary ataxia.

Olfaction in Parkin carriers in Chinese patients with Parkinson disease.

BACKGROUND: Olfactory identification was reported to be better among PD (Parkinson disease) patients with Parkin mutations, but previous studies didn't eliminate the interference of other PD related genes on olfaction, and whether olfaction of Parkin mutations patients was better in Chinese population was still unknown. OBJECTIVE: To assess olfaction function among PD patients with Parkin mutations in Chinese population. MATERIALS AND METHODS: A total of 226 PD patients with a positive family history or an early-onset age (<50 years) were enrolled for genetic testing of PD related genes by target sequencing and multiple ligation-dependent probe amplification. The clinical data including olfactory function test were investigated. Linear regression was performed to adjust for the covariates between all groups. RESULTS: There were 68 patients found having a negative result in PD genetic testing and 43 patients carrying homozygous or compound heterozygous Parkin mutations. Among them, 49 PD panel negative patients and 33 PD-Parkin patients had results of olfactory assessment. PD -Parkin patients performed significantly better on the Sniffin' Sticks tests than panel negative patients (8.0 ± 1.7 vs. 5.7 ± 1.9, p < .001), but still worse compared to healthy controls (9.4 ± 1.5, p = .003). These differences persisted after adjusting for confounders. CONCLUSIONS: Among Chinese population, PD -Parkin patients had relatively preserved olfaction compared to PD panel negative patients after eliminating the interference of other PD related genes, but were still worse than healthy controls.

The heterozygous R1441C mutation of leucine-rich repeat kinase 2 gene in a Chinese patient with Parkinson disease: A five-year follow-up and literatures review.

BACKGROUND: Leucine-rich repeat kinase 2 gene (LRRK2) was recognized associated with both familial and sporadic Parkinson Disease (PD). Seven missense mutations (G2019S, R1441C, R1441G, R1441H, Y1699C, I2020T, N1437H) of it have been confirmed disease- causing. They were common among Caucasian PD patients, but rarely reported in Asian, especially in Chinese Han population. OBJECTIVES: We aimed to identify the frequencies of these seven mutations of LRRK2 in Chinese early-onset PD (EOPD) patients and analyze the phenotypes. METHODS: One hundred and thirty seven EOPD patients were enrolled for genetic testing. The seven disease-causing mutations of LRRK2 were carried out by target sequencing using Illumina HiSeq 2000 Sequencer. The identified variants were further confirmed by Sanger sequence. The clinical materials were investigated retrospectively. RESULTS: Only one patient (0.73%) was found carrying pathogenetic LRRK2 mutation of R1441C. The age at onset of the female patient was 44. She manifested typical motor symptoms of PD and responded well to levodopa therapy. Longitudinal evaluation showed progression of motor symptoms and depression but no cognitive impairment. The dopamine transporter (DAT) imaging via [11C]-2ß-carbomethoxy-3ß-(4-fluorophenyl) tropan (CFT) and Positron emission computed tomography (PET) revealed typical dopamine transporter uptake reduction. CONCLUSIONS: The LRRK2 R1441C mutation was found in a Chinese EOPD patient for the first time. The manifestations of LRRK2-R1441C carriers were indistinguishable from sporadic PD patients.

Odor Identification Test in Idiopathic REM-Behavior Disorder and Parkinson's Disease in China.

BACKGROUND: Olfactory dysfunction is common in Parkinson's disease (PD) and idiopathic rapid eye movement sleep behavior disorder (iRBD), which is a risk factor in the development of PD. However, a few studies have conflicting results when comparing dysosmia in the patients with iRBD and PD. There is no study investigating the olfactory function in Chinese patients with iRBD. Additionally, the Sniffin' Sticks screening 12 test (SS-12) contains several odors that are not familiar to people in different cultures. METHODS: Odor identification was evaluated in iRBD patients (n = 54), PD patients (n = 54) and healthy controls (n = 54). With the identification data, a brief odor identification test was established and then validated in other subjects. RESULTS: Odor identification scores in iRBD patients were significantly higher than those in PD patients (P<0.001) but lower than those in controls (P<0.001). At the cut-off value of 7.5, the Sniffin' Sticks clearly differentiated iRBD and PD patients from the controls, and the brief test could increase the specificity in diagnosing PD. Neither the Sniffin' Sticks nor the brief test could clearly differentiate PD and iRBD patients from each other. CONCLUSIONS: Olfaction is more impaired in PD patients than in iRBD patients, possibly due to the heterogeneity of iRBD patients. The Sniffin' Sticks could be a useful tool for differentiating iRBD patients from the healthy population, and it could be useful for screening people at high-risk of PD in China, especially when combined with polysomnography. To reduce the expense and time required for the Sniffin' Sticks test, this study shows that a brief test is feasible.

The heterozygous A53T mutation in the alpha-synuclein gene in a Chinese Han patient with Parkinson disease: case report and literature review.

The missense mutation A53T of alpha-synuclein gene (SNCA) was reported to be a rare but definite cause of sporadic and familial Parkinson disease (PD). It seemed to be restricted geographically in Greece and Italy. We aimed to identify the SNCA mutations in a Chinese PD cohort. Ninety-one early onset PD patients or familial PD probands were collected consecutively for the screening of PD-related genes. The genetic analysis was carried out by target sequencing of the exons and the corresponding flanking regions of the PD-related genes using Illumina HiSeq 2000 sequencer and further confirmed by Sanger sequencing or restriction fragment length polymorphism. Dosage mutations of exons in these genes were carried out by multiple ligation-dependent probe amplification. Among the 91 patients, we found only one heterozygous mutation of SNCA A53T, in a 23-year-old male patient with negative family history. The [(11)C]-2ß-carbomethoxy-3ß-(4-fluorophenyl) tropan (CFT) PET and PD-related spatial covariance pattern (PDRP) via [(18)F]-fluorodeoxyglucos (FDG) PET confirmed a typical pattern of PD. After examining his parents, we found his mother was an asymptomatic carrier, with declined hand dexterity detected by quantitative motor tests. Reduced dopamine transporter uptake of his mother was identified by CFT PET, and abnormal PDRP pattern was found by FDG PET. Our investigation expanded the clinical and genetic spectrum of Chinese PD patients, and we suggested SNCA mutations to be screened in familial and early onset Chinese PD patients.

Novel LAMP2 mutations in Chinese patients with Danon disease cause varying degrees of clinical severity.

AIMS: Danon disease is an Xlinked dominant lysosomal glycogen storage disorder characterized by cardiomyopathy, skeletal myopathy, and mental retardation. This study described two Chinese cases of Danon disease in order to broaden the phenotypic and genetic spectrum. METHODS: Clinical data were collected and LAMP2 mutations were analyzed. RESULTS: Patient A had fluctuating limb weakness during 6 months follow-up and was diagnosed with drug-induced myopathy due to anti-hepatitis B therapy with lamivudine. However, the first muscle biopsy with large cytoplasmic vacuoles confused the diagnosis and led to the second biopsy that allowed for the final diagnosis. Patient B had severe cardiac disturbances leading to sudden death. Molecularly, patient A harbored a synonymous mutation adjacent to the exon 6-intron 6 junction; mRNA analysis provided evidence that totally abolished the donor site and caused skipping of exon 6. Patient B harbored a frame-shift deletion mutation in exon 3 (c.396delA) leading to a truncated protein. DISCUSSION: To our knowledge, this is the first report of Danon disease caused by a synonymous exon mutation that affected mRNA splicing, which indicates that a synonymous substitution may not be silent when it is in the exon sequences close to the splice sites. It is also the first description of Danon disease clinically presenting as druginduced myopathy at onset; the pathological changes might be the key point for making a differential diagnosis. *These two authors contributed equally to this work.