Adult-onset very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD).

BACKGROUND AND PURPOSE: Very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is a hereditary disorder of mitochondrial long-chain fatty acid oxidation that has variable presentations, including exercise intolerance, cardiomyopathy and liver disease. The aim of this study was to describe the clinical and genetic manifestations of six patients with adult-onset VLCADD. METHODS: In this study, the clinical, pathological and genetic findings of six adult patients (four from Iran and two from Serbia) with VLCADD and their response to treatment are described. RESULTS: The median (range) age of patients at first visit was 31 (27-38) years, and the median (range) age of onset was 26.5 (19-33) years. Parental consanguinity was present for four patients. Four patients had a history of rhabdomyolysis, and the recorded CK level ranged between 67 and 90 000 IU/l. Three patients had a history of exertional myalgia, and one patient had a non-fluctuating weakness. Through next-generation sequencing analysis, we identified six cases with variants in the ACADVL gene and a confirmed diagnosis of VLCADD. Of the total six variants identified, five were missense, and one was a novel frameshift mutation identified in two unrelated individuals. Two variants were novel, and three were previously reported. We treated the patients with a combination of L-carnitine, Coenzyme Q10 and riboflavin. Three patients responded favorably to the treatment. CONCLUSION: Adult-onset VLCADD is a rare entity with various presentations. Patients may respond favorably to a cocktail of L-carnitine, Coenzyme Q10, and riboflavin.

Molecular genetic and clinical characterization of myotonic dystrophy type 1 patients carrying variant repeats within DMPK expansions.

Myotonic dystrophy type 1 (DM1) is caused by a highly unstable expansion of CTG repeats in the DMPK gene. Its huge phenotypic variability cannot be explained solely by the repeat number. Recently, variant repeats within the DMPK expansions have emerged as potential disease modifiers. The frequency of variant expanded alleles was estimated in 242 DM1 patients from 174 Serbian families using repeat-primed PCR (RP-PCR). The patterns of variant repeats were determined by direct sequencing of RP-PCR or PCR products. PCR-based southern blot was performed to get insight into the intergenerational mutational dynamics of variant expanded alleles. All patients carrying variant repeats were clinically re-examined. Variant repeats were observed in eight patients from five families (2.9%). They were detected only at the 3' end of DMPK expansions. CCG variant repeats were present in seven patients, either as a part of regular runs of CCGCTG hexamer, individual repeats, or CCG blocks. Analyses of three intergenerational transmissions revealed a considerable stability or likely a contraction of variant expanded alleles. Intriguingly, a decrease in age at onset accompanied these transmissions. Overall, patients were characterized by a milder phenotype and/or some atypical symptoms that could be rather clinically suggestive of myotonic dystrophy type 2. In addition, the first case of de novo CTC variant repeat was observed. Variant repeats might explain a part of the phenotypic variability in a small percent of DM1 patients and likely display a stabilizing effect on the meiotic instability of DMPK expanded alleles.

Prospective measurement of quality of life in myotonic dystrophy type 1.

INTRODUCTION: Generic patient reported outcome measures have had varied success in tracking QoL in myotonic dystrophy type 1 (DM1). AIM: To analyze changes of Individualized Neuromuscular Quality of Life questionnaire (INQoL) scores in clinic patients with DM1 over a 6-year period. METHOD: Patients completed the INQoL at baseline and after a 6-year period through their attendance in a neurology outpatient clinic. Severity of muscular involvement in DM1 was analyzed using the Muscular Impairment Rating Scale (MIRS). RESULTS: Ninety-nine DM1 patients completed a baseline visit. Sixty-seven of these patients were retested at an interval time. The overall INQoL score improved in our sample of patients (P<.05) as did the following subscales: myotonia (P<.05), pain (P<.05), activities (P<.01), social relationships (P<.01), and body image (P<.05). No changes were observed for the independence and emotions scales. There were no differences in mean change of INQoL scores between patients with worsened MIRS and those with no change in MIRS scale after follow-up (P>.05). CONCLUSION: Individualized Neuromuscular Quality of Life questionnaire scores improved in our cohort of DM1 patients during a 6-year period. INQoL score did not correlate with progression of muscle weakness. This must be better understood before the selection of the instrument for use in trials to measure therapeutic benefit in DM1 patients.

Five-year study of quality of life in myotonic dystrophy.

Background - Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults. There is a complete lack of studies that assessed quality of life (QoL) trajectory during time in DM1 cohorts. Aim - To analyze changes of QoL in patients with DM1 during a 5-year follow-up period and to assess responsiveness of the SF-36 questionnaire. Patients and Method - At the baseline, this study comprised 84 DM1 patients, of whom 62 were retested after the mean period of 64.2 ± 3.9 months. Severity of muscular weakness was assessed using the Muscular Impairment Rating Scale (MIRS). Patients completed Serbian version of the SF-36 questionnaire as a measure of health-related QoL. Results - After 5 years, MIRS score of our DM1 patients showed significant progression of 0.5 grade (P < 0.01). All mental subdomains, role physical, and total SF-36 scores significantly improved after 5 years (P < 0.01). Unexpectedly, worsening of muscular weakness from mild to severe was in association with improvement of QoL. Conclusion - QoL improved in our cohort of DM1 patients during a 5-year period despite the progression of the disease. SF-36 should be used with caution as a patient-reported outcome measure in DM1 clinical trials.

A comprehensive analysis of the epidemiology and clinical characteristics of anti-LRP4 in myasthenia gravis.

Double-seronegative myasthenia gravis (dSN-MG, without detectable AChR and MuSK antibodies) presents a serious gap in MG diagnosis and understanding. Recently, autoantibodies against the low-density lipoprotein receptor-related protein 4 (LRP4) have been identified in several dSN-MG sera, but with dramatic frequency variation (∼2-50%). We have developed a cell based assay (CBA) based on human LRP4 expressing HEK293 cells, for the reliable and efficient detection of LRP4 antibodies. We have screened about 800 MG patient sera from 10 countries for LRP4 antibodies. The overall frequency of LRP4-MG in the dSN-MG group (635 patients) was 18.7% but with variations among different populations (range 7-32.7%). Interestingly, we also identified double positive sera: 8/107 anti-AChR positive and 10/67 anti-MuSK positive sera also had detectable LRP4 antibodies, predominantly originating from only two of the participating groups. No LRP4 antibodies were identified in sera from 56 healthy controls tested, while 4/110 from patients with other neuroimmune diseases were positive. The clinical data, when available, for the LRP4-MG patients were then studied. At disease onset symptoms were mild (81% had MGFA grade I or II), with some identified thymic changes (32% hyperplasia, none with thymoma). On the other hand, double positive patients (AChR/LRP4-MG and MuSK/LRP4-MG) had more severe symptoms at onset compared with any single positive MG subgroup. Contrary to MuSK-MG, 27% of ocular dSN-MG patients were LRP4 antibody positive. Similarly, contrary to MuSK antibodies, which are predominantly of the IgG4 subtype, LRP4 antibodies were predominantly of the IgG1 and IgG2 subtypes. The prevalence was higher in women than in men (female/male ratio 2.5/1), with an average disease onset at ages 33.4 for females and 41.9 for males. Overall, the response of LRP4-MG patients to treatment was similar to published responses of AChR-MG rather than to MuSK-MG patients.

Cerebrospinal fluid biomarkers of neurodegeneration in patients with juvenile and classic myotonic dystrophy type 1.

BACKGROUND AND PURPOSE: The aim of the present study was to analyze cerebrospinal fluid (CSF) levels of total tau (T-tau), phosphorylated tau (P-tau) and the 42-amino-acid form of ß-amyloid (Aß42 ) in patients with myotonic dystrophy type 1 (DM1), and their possible correlations with cognitive and behavioral manifestations in these patients. METHODS: Lumbar puncture was performed in 74 patients with DM1 [27 with the childhood/juvenile form (jDM1) and 47 with the adult form (aDM1) of the disease] and 26 control subjects who were subjected to orthopedic surgery. Sandwich ELISA was used for measuring the levels of T-tau, P-tau and Aß42. RESULTS: The CSF level of Aß42 was at its lowest in patients with jDM1 and at its highest in controls (P < 0.05). A tendency of T-tau and P-tau to increase was greater in aDM1 patients than in jDM1 patients and controls (P > 0.05). In both jDM1 and aDM1 patients, significant correlations were found between Aß42 and T-tau (rho = 0.81 and rho = 0.67, respectively, P < 0.01), as well as between Aß42 and P-tau (rho = 0.87 and rho = 0.67, respectively, P < 0.01). The Aß42/P-tau ratio decreased with age in aDM1 patients (rho = -0.30, P < 0.05). Only the level of Aß42 in the CSF of jDM1 patients was correlated with the size of the CTG expansion (rho = -0.53, P < 0.05). Only a few correlations were observed between levels of biomarkers and neuropsychological testing. CONCLUSION: The CSF level of Aß42 was decreased in patients with jDM1, whilst the Aß42/P-tau ratio was decreased in aDM1 patients. Positive correlations between Aß42 , T-tau and P-tau were observed in both forms of disease. Further studies with larger cohorts of DM1 patients are necessary.

Dependent and paranoid personality patterns in myotonic dystrophy type 1.

OBJECTIVES: To analyze frequency and type of personality pattern in patients with myotonic dystrophy type 1 (DM1), to correlate these findings with clinical data, and to assess its possible influence on quality of life (QoL). MATERIALS AND METHODS: This cross-sectional study comprised 62 patients with DM1. Following measures were used: Muscular Impairment Rating Scale, Raven's Standard Progressive Matrices (RSPM), Millon Multiaxial Clinical Inventory I (MMCI), SF-36, and Individualized Neuromuscular Quality of Life (INQoL) questionnaires. RESULTS: The presence of at least one pathological personality trait with score above 85 on MMCI was found in 47 (75.8%) patients. After clinical interview, 36 (58.1%) subjects had significant personality impairment. The most common personality trait in our cohort of patients was dependent found in 51.6% of patients, followed by paranoid (38.7%). Higher score on dependent personality scale correlated with lower education (rho = -0.251, P = 0.049). Dependent personality scores significantly differed between patients with physical and intellectual work (93.1 ± 8.9 vs 66.9 ± 31.7, P = 0.011). Paranoid score was higher in patients with lower education (rho = -0.293, P = 0.021), lower score on RSPM test (rho = -0.398, P = 0.004) and larger number of CTG repeats (rho = 0.254, P = 0.046). Presence of dependent personality was not in association with QoL scores (P > 0.05). On the other hand, patients with paranoid personality trait had worse QoL than those without it (P < 0.05). CONCLUSION: Almost 60% of our patients with DM1 had clinically significant personality impairment, with dependent and paranoid personality patterns being the most common. Paranoid personality may decrease QoL in these patients, which gives us new opportunities for symptomatic therapy in DM1.

Epidemiological study of adult-onset myasthenia gravis in the area of Belgrade (Serbia) in the period 1979-2008.

BACKGROUND: The aim of this study was to analyze the prevalence and incidence of adult-onset myasthenia gravis (MG) in the Belgrade population from 1979 to 2008. METHODS: Data on the number of MG patients and their basic demographic and clinical characteristics were collected from hospital records (1979-1992) and the Belgrade MG Registry (1993-2008). Incidence and prevalence were standardized by the direct method (using the world standard population). A time-trend analysis of MG incidence was performed using a linear regression model. RESULTS: During the study period 562 cases (316 women, 246 men) were registered. On December 31st, 2008, the standardized prevalence (according to the world standard population) was 188.3/1,000,000 (women: 237.8/1,000,000; men: 139.4/1,000,000). The average annual standardized incidence rate was 13.3/1,000,000 (women: 14.1/1,000,000; men: 12.2/1,000,000). The incidence rates tended to increase significantly in both sexes during the study period (y = 3.299 + 14.363x, p = 0.002). Age-specific incidence rates for women demonstrated a bimodal pattern, with the first peak in the 20- to 29-year age group and the second one in the ≥70-year group. For both genders, an increase in age-specific incidence rates was registered for all age groups, although this was significant (p = 0.001) only for an MG onset of ≥60 years of age. CONCLUSIONS: The study confirms an increase in the incidence of MG in the area of Belgrade during the study period, especially for those with MG onset after 60 years of age.

Kidney biopsy in patients with diabetes mellitus.

BACKGROUND: The clinical consequences of the results obtained by kidney biopsy in patients with diabetes mellitus Type 1 or Type 2 have been controversial. Our study was conducted to assess clinical symptoms and histological diagnoses in patients with diabetes mellitus Type 1 and Type 2 undergoing kidney biopsy. DESIGN, SETTING AND PATIENTS: Observational study. The study included data from 567 consecutive renal biopsies of patients with diabetes mellitus Type 1 or 2 and chronic kidney disease (CKD) examined by standard histopathological procedures. The main outcome measures were incidence of diabetic nephropathy (DN) and glomerulonephritis (GN), predictors for the presence of both DN or GN. RESULTS: Approximately 70% of patients with diabetes mellitus Type 1 or 2 and evidence for CKD had DN. Glomerular diseases present in approximately 30% of patients with diabetes were predominantly immune complex GN and secondary focal glomerulosclerosis, followed by IgA-GN, which was associated with microhematuria (p = 0.01) and hypertension (p = 0.04). Only a minority had membranous GN, which was associated with nephrotic syndrome (p = 0.004). Progressive CKD predicted the presence of GN in diabetes mellitus Type 2 (r = -0.98; p = 0.02). CONCLUSION: GN is not uncommon in patients with diabetes and evidence for CKD. Kidney biopsy should therefore be considered in patients with diabetes and progressive CKD.

Validation of Serbian version of the disease-specific myasthenia gravis questionnaire.

AIM: The aim of this study was to validate translated and cross-cultural adapted Italian version of myasthenia gravis-specific questionnaire (MGQ) in Serbian MG patients. MATERIALS AND METHODS: The questionnaire was validated in 140 consecutive MG patients from Belgrade. In each patient association between the total MGQ score and form and severity of the disease was determined. Also, correlation between regional domain scores of MGQ and main clinical findings according to Besinger's clinical score was analyzed. RESULTS: Patients' participation in the assessment was satisfactory with excellent internal consistency and reproducibility. Total MGQ score, as well as domain scores, correlated with highly significant inverse relationship with the disease severity and clinical status of patients at the moment of completing the questionnaire. Furthermore, the bulbar domain of the questionnaire appeared more specific and sensitive than clinical history and examination. CONCLUSION: We concluded that the Serbian version of the MGQ may be useful as a measure of clinical outcome in patients with MG.

Leptin and the metabolic syndrome in patients with myotonic dystrophy type 1.

OBJECTIVES: To evaluate serum leptin concentration and its relation to metabolic syndrome (MSy) in non-diabetic patients with myotonic dystrophy type 1 (DM1). MATERIALS AND METHODS: This study included 34 DM1 patients, and the same number of healthy subjects matched for age, sex and body mass index (BMI). RESULTS: DM1 patients had increased BMI and insulin resistance, and increased leptin and insulin concentrations, but the other features of MSy such as diabetes, glucose intolerance and hypertension were not detected in DM1 patients. Serum leptin levels were higher in patients with DM1 than in healthy controls (8.5 +/- 6.6 ng/ml vs 3.6 +/- 2.9 ng/ml in men, and 13.9 +/- 10.0 ng/ml vs 10.9 +/- 6.9 ng/ml in women, respectively). In DM1 patients, leptin levels correlated with BMI, fasting insulin and insulin resistance (HOMA) (P < 0.01). CONCLUSIONS: The leptin overproduction correlated with insulin resistance in DM1 patients but the significance of this finding remains unclear.

Health-related quality of life in patients with myotonic dystrophy type 1 and amyotrophic lateral sclerosis.

The aim was to assess factors that might influence health-related quality of life (HRQoL) in patients with two different neuromuscular disorders - myotonic dystrophy type 1 (DM1) and amyotrophic lateral sclerosis (ALS). A cross-sectional study was performed on 79 patients with DM1 and 74 with ALS. The HRQoL was evaluated by SF-36, Serbian version. Depressive and anxiety symptoms were assessed using the Hamilton rating scale for depression and the Hamilton rating scale for anxiety respectively. Severity of muscular involvement in DM1 was measured with MRC scale and severity of ALS with ALSFRSr score. The mean total score as well as all domain scores of SF-36 were similar in DM1 and ALS patients (p > 0.05), except that ALS patients experienced less bodily pain (p < 0.05). Depressiveness was found in 51% and marked anxiety in 38% of DM1 patients. Emotional status and severity of muscular involvement emerged as significant independent contributing factors to the total SF-36 in DMI patients (p < 0.05). Only 3% of ALS patients showed depressiveness and 4% anxiety symptoms. The factors found to contribute to HRQoL in ALS patients were severity of disease and educational level ofpatients (p < 0.05). We found significant percentage of potentially treatable emotional disturbances which together with severity of disease significantly contributed to HRQoL in DM1 patients. On the other hand, in ALS patients depressiveness and anxious symptoms were uncommon and the factors found to contribute to HRQoL were severity of disease and educational level.

Prospective analysis of gait characteristics in chronic inflammatory demyelinating polyradiculoneuropathy.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a disorder that may lead to functional impairment, including gait abnormalities. Our aim was to analyze gait characteristics in patients with CIDP compared to healthy controls (HC). Moreover, we sought to determine changes of gait parameters after six-month follow-up period. Twenty-four patients with CIDP and 24 HCs performed basic walking task, dual-motor task, dual-mental task, and combined task using the same GAITRite system. Lower limb MRC-SS and lower limb INCAT disability score were assessed. Fourteen patients were retested after six months. Majority of gait parameters showed significant differences in all experimental conditions when compared between CIDP and HCs. The most consistent findings in CIDP were shorter stride length (SL), prolonged cycle time (CT) and double support time (DS), as well as increased variation of SL and of swing time (ST) (p < 0.05). During follow-up, INCAT improved in nine (64.3%) of 14 patients and MRC-SS improved in eight (57.1%) patients. Six-month changes of CT and its variation during combined task significantly differentiated patients with improved vs. non-improved INCAT (p < 0.05). In conclusion, patients with CIDP had slower gait with prolonged DS and with shorter SL compared to HCs. Increased variation of SL and of ST in CIDP may suggest a potential risk for instability and falls. Shorter CT duration and less CT variation during time correlated well with improvement in disability.

Intravenous immunoglobulin therapy in two patients with myasthenia gravis and pemphigus vulgaris.

UNLABELLED: Various forms of pemphigus have been reported to occur with myasthenia gravis (MG), with and without thymoma. We described two cases of pemphigus vulgaris associated with MG without thymoma. Case 1. A 44 year-old woman presented with 3 years history of pemphigus vulgaris. Three years later, she developed myasthenic symptoms with elevated level of anti-acetylcholine receptor (AChR) antibodies - 5.2 nmol/L. She was thymectomised and we revealed only hyperplastic thymus. Case 2. A 64-year-old woman had a general fatigue and intermittent double vision. She was diagnosed as MG three years later. Two months before she diagnosed as MG, she had pruritic erythematous, erosive and bullous lesions on her body and extremities. Oral prednisolon, pyridostigmine bromide and azathioprine or cyclophosphamide didn't adequately control MG and pemphigus in our patients, so they received intravenous immunoglobulins of 0.4 g/kg for 5 consecutive days. After that therapy, our patients markedly improved. CONCLUSION: The precise pathological mechanisms of the association between pemphigus and MG are not fully understood. The thymus has been suggested to be a possible common origin of autoimmune response in these disorders.

Corticosteroids in chronic inflammatory demyelinating polyneuropathy : A retrospective, multicentre study, comparing efficacy and safety of daily prednisolone, pulsed dexamethasone, and pulsed intravenous methylprednisolone.

BACKGROUND: Chronic inflammatory demyelinating polyneuropathy (CIDP) can be treated with corticosteroids or intravenous immunoglobulins. Various corticosteroid regimens are currently used in CIDP, but it is unknown whether they are equally efficacious. In this retrospective study, we compared efficacy and safety of three corticosteroid regimens in CIDP patients. METHODS: We included treatment naïve patients that fulfilled the EFNS/PNS criteria for CIDP. Patients were treated with corticosteroids according to the local protocol of three CIDP expertise centres. Corticosteroid regimens consisted of daily oral prednisolone, pulsed oral dexamethasone, or pulsed intravenous methylprednisolone. Outcomes were number of responders to treatment, remission rate of treatment responders, overall probability of 5-year remission, and the occurrence of adverse events. RESULTS: A total of 125 patients were included. Sixty-seven (54%) patients received daily prednisone or prednisolone, 37 (30%) pulsed dexamethasone, and 21 (17%) pulsed intravenous methylprednisolone. Overall, 60% (95% CI 51-69%) responded to corticosteroids, with no significant difference between the three treatment regimens (p = 0.56). From the 75 responders, 61% (95% CI 50-73%) remained in remission, during a median follow-up of 55 months (range 1-197 months). The probability of responders reaching 5-year remission was 55% (95% Cl 44-70%), with no difference between the three groups. Adverse events leading to a change in treatment occurred in ten patients (8%). Two patients had a serious adverse event. CONCLUSION: Corticosteroids lead to improvement in 60% of patients and to remission in 61% of treatment responders. There were no differences between treatment modalities in terms of efficacy and safety.

Neuromyelitis Optica in a Patient from Family with both Myotonic Dystrophy Type 1 and 2.

INTRODUCTION: The aim of this study was to present a family co-segregating myotonic dystrophy type 1 (DM1) and 2 (DM2), and one member affected with neuromyelitis optica (NMO). CASE REPORT: Index case underwent cataract surgery at age 39. Although she had no muscle symptoms, genetic testing revealed a DM2 mutation and a DM1 protomutation. The patient noticed difficulties in climbing stairs at age 47. Clinical examination showed mild muscle weakness, calf hypertrophy, mild myotonia and several multisystem signs. Patient's mother had DM1 protomutation and clinically exhibited only cataract. Two proband's sisters, one with DM2 mutation and another with DM2 mutation and DM1 protomutation, had a clinical presentation similar to the index case. In addition, the latter also developed NMO. CONCLUSION: Our findings suggest that screening for both DM1 and DM2 should be done and a positive result in either gene should not be an indication to stop screening, but to move to the other gene.

Comparison of temporal and stride characteristics in myotonic dystrophies type 1 and 2 during dual-task walking.

OBJECTIVE: We analyzed temporal and stride characteristics in patients with myotonic dystrophy type 1 (DM1) and type 2 (DM2) while performing dual mental and motor tasks, and investigated correlations between gait parameters and cognitive impairments. METHOD: Dual-task walking was performed by 37 patients (20 DM1 and 17 DM2) and 48 healthy subjects divided into two groups, age- and gender-matched control group for DM1 (HC1) and age- and gender-matched control group for DM2 (HC2). The subjects performed a basic walking task, dual-motor task, dual-mental task, and combined motor and mental task. RESULTS: DM1 and DM2 patients differed significantly in temporal and stride characteristics compared to HC. Main differences in DM1 were slower gait and shorter stride length, while both DM1 and DM2 patients had a higher degree of variation of the swing time during dual-task gait, a parameter that reflects posture and balance. Impact of the cognitive dual task on gait pattern changes was also observed. Visuospatial ability correlated with gait changes in DM1, while executive functions had stronger influence in DM2 (p<0.01). Both patient groups had leg muscle weakness. CONCLUSION: Gait pattern was impaired in both patient groups concerning temporal and stride characteristics. Dual-task walking paradigm may discover mild initial gait changes and could provide early identification of fall risks and predict possible falls in DM patients.

Titin antibodies in "seronegative" myasthenia gravis--A new role for an old antigen.

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction of skeletal muscles. Triple-seronegative MG (tSN-MG, without detectable AChR, MuSK and LRP4 antibodies), which accounts for ~10% of MG patients, presents a serious gap in MG diagnosis and complicates differential diagnosis of similar disorders. Several AChR antibody positive patients (AChR-MG) also have antibodies against titin, usually detected by ELISA. We have developed a very sensitive radioimmunoprecipitation assay (RIPA) for titin antibodies, by which many previously negative samples were found positive, including several from tSN-MG patients. The validity of the RIPA results was confirmed by western blots. Using this RIPA we screened 667 MG sera from 13 countries; as expected, AChR-MG patients had the highest frequency of titin antibodies (40.9%), while MuSK-MG and LRP4-MG patients were positive in 14.6% and 16.4% respectively. Most importantly, 13.4% (50/372) of the tSN-MG patients were also titin antibody positive. None of the 121 healthy controls or the 90 myopathy patients, and only 3.6% (7/193) of other neurological disease patients were positive. We thus propose that the present titin antibody RIPA is a useful tool for serological MG diagnosis of tSN patients.

MuSK autoantibodies in myasthenia gravis detected by cell based assay--A multinational study.

Seronegative myasthenia gravis (MG) presents a serious gap in MG diagnosis and understanding. We applied a cell based assay (CBA) for the detection of muscle specific kinase (MuSK) antibodies undetectable by radioimmunoassay. We tested 633 triple-seronegative MG patients' sera from 13 countries, detecting 13% as positive. MuSK antibodies were found, at significantly lower frequencies, in 1.9% of healthy controls and 5.1% of other neuroimmune disease patients, including multiple sclerosis and neuromyelitis optica. The clinical data of the newly diagnosed MuSK-MG patients are presented. 27% of ocular seronegative patients were MuSK antibody positive. Moreover, 23% had thymic hyperplasia suggesting that thymic abnormalities are more common than believed.