Tacrolimus as Single-Agent Immunotherapy and Minimal Manifestation Status in Nonthymoma Myasthenia Gravis

Background. Tacrolimus is a second-line immunosuppressant in myasthenia gravis (MG) therapy, which is mainly used in combination with corticosteroids to reduce steroid dose and maintain the effect of immunotherapy. However, few studies have focused on the effect of tacrolimus as single-agent immunotherapy on achieving minimal manifestation status (MMS). Thus, this study is aimed at exploring the efficacy and influencing factors of tacrolimus as single-agent immunotherapy in MG. Methods. Clinical data of 75 nonthymoma MG patients treated with tacrolimus single-agent as initial immunotherapy were retrospectively analyzed. The therapeutic effect was evaluated by Myasthenia Gravis Foundation of America postintervention status. Clinical factors affecting the achievement of MMS and treatment reactivity of different MG subtypes were determined by Cox regression analysis. Results. Tacrolimus was generally safe, with only two patients (2.7%) switching medications due to side effects. 32% of patients had improved symptoms after 1 month of treatment. 69.2% of patients achieved MMS or better after one year. The age < 39 years old, QMG score < 11 points, and AChR − Ab titer < 8.07 nmol / L were indicative of a favorable response, which was independent of gender, course of the disease. As for MG subtypes, ocular and seronegative MG showed better treatment sensitivity. Conclusions. Tacrolimus as single-agent immunotherapy takes effect quickly and can effectively enable nonthymoma MG patients to achieve MMS. Tacrolimus can be used alone for the initial immunotherapy of MG patients, especially for young, mild, and low antibody titer patients.

High κ free light chain is a potential biomarker for double seronegative and ocular myasthenia gravis

ObjectiveTo investigate the hypothesis that free light chain (FLC) sera levels could serve as a biomarker for myasthenia gravis (MG), especially for the subgroups of seronegative MG and ocular MG.MethodsSera from 73 patients with MG (20 seronegative for antiacetylcholine receptor [AChR] and anti–muscle-specific kinase and 53 positive for anti-AChR, which were clinically divided into 24 patients with ocular type, 45 with generalized type, and 4 with unequivocal clinical manifestation) and 49 healthy controls were studied for κ FLC and λ FLC levels with the Freelite human FLC kits.ResultsThe κ but not the λ levels of FLC were significantly increased in the patients with MG, including those with double seronegative MG and ocular MG, compared with the healthy controls. The specificity for double seronegative MG and ocular MG were both 98.0% when κ FLC was ≥25.0 mg/L. Increased κ FLC levels were not affected by the patient's sex, age at MG onset, the presence of thymic pathology, or different treatments.ConclusionsElevated serum κ FLC may serve as a biomarker for MG in suspected patients who are double seronegative and in those with only ocular manifestations when serology is inconclusive.Classification of evidenceThis study provides Class III evidence that high κ FLC levels distinguished patients with MG, including those who were double seronegative, from healthy controls.

Case Report: Malignant Thymoma And Seronegative Myasthenia Gravis

Myasthenia gravis (MG) is present in 50% of thymomas and is rarely associated with thymic carcinoma. We present the case of a 49-year-old woman with malignant thymoma, treated with surgery followed by radiotherapy, and a late seronegative MG diagnosis. This case reports the importance of a multidisciplinary approach to the management of the potential correlation of malignant and benign diseases.

Myasthenia gravis induced by avelumab

Neurological immune-related adverse events are potentially life-threatening complications of immune checkpoint inhibitors. Myasthenia gravis (MG) is a rare complication of treatment with inhibitors of programmed cell death protein 1 (PD)-1 and PD ligand 1 (PD-L1). We present a patient who developed seronegative MG resulting in respiratory failure while being treated with avelumab for metastatic, treatment-refractory ovarian cancer. Her MG went into remission following steroids and maintenance intravenous immunoglobulin treatment. We conclude that MG is a rare, but potentially life-threatening immune-related adverse event of avelumab therapy. This case provides support to the hypothesis that PD-1/PD-L1 signaling may have a protective role in MG.

098 A case of myasthenia gravis lambert eaton overlap syndrome (MLOS) in seronegative myasthenia gravis

IntroductionMyasthenia gravis (MG) is an antibody-mediated autoimmune disease of neuromuscular transmission. 6 to 12 percent of MG are negative for acetyl choline receptor (AChR) and MuSK antibodies and are defined as seronegative MG. Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune condition with antibodies to presynaptic voltage-dependent calcium channelCaseA 39 year old male presented with blurred vision and right-sided ptosis. Initial examination showed a pupil-sparing left complete third nerve palsy. Demyelination and intracranial aneurysms were ruled out with gadolinium-enhanced MRI/MRA. Outpatient follow-up 2 weeks later showed new onset proximal muscle weakness of the upper limbs with fatigability and a complex ophthalmoplegia with almost complete paralysis of gaze. A repeat MRI with gadolinium and CSF analysis were normal. His AChR and MuSK antibodies were negative; however, voltage-dependent calcium channel antibodies, ANA, dsDNA, and SSA were positive. Initial nerve conduction tests were normal, but repeat NCS on two separate occasions showed decrement on repetitive stimulation in the right trapezius with no evidence of facilitation post exercise. CT chest, abdomen and pelvis was normal. He improved with pulsed steroids and was discharged on a tapering dose of oral steroids, pyridostigmine and regular IVIG infusions as a steroid-sparing agent.ConclusionLambert-Eaton myasthenic syndrome shares the same pathologic site and similar pathophysiology with MG but has a markedly different clinical and electro-physiological picture. There are reports of MG and LEMS overlap syndrome, however, they exhibit phenotypic characteristics of both LEMS and MG. Voltage-dependent calcium channel antibodies have not been described in patients with seronegative MG. Ours is potentially the first reported case of seronegative myasthenia with voltage-dependent calcium channel antibodies and only clinical and neurophysiological features of MG.

A 5-Year Follow-Up of Triple-Seronegative Myasthenia Gravis Successfully Treated with Tacrolimus Therapy

Seronegative myasthenia gravis (MG) is a generalized form of MG that is diagnosed on the basis of clinical symptoms, electrophysiological testing, and pharmacological responses, in the absence of a seropositive status for anti-acetylcholine receptor (AChR) antibodies. Generalized MG that is seronegative for anti-AChR, anti-muscle-specific kinase (MuSK), and anti-low density lipoprotein receptor related protein 4 (Lrp4) antibodies is known as triple-seronegative MG. We here describe a case of triple-seronegative MG in an 8-year-old boy. His first symptom was dysphagia, at 3 years of age, and he subsequently developed ptosis, rhinolalia, and a waddling gait. A genetic analysis was conducted to exclude the possibility of congenital myasthenia syndrome due to the patient's resistance to steroid therapy. His condition was successfully managed with tacrolimus therapy over a 5-year follow-up period. Recently, several studies have reported the therapeutic utility of tacrolimus in juvenile seropositive MG; in contrast, a few reports have described tacrolimus treatment in cases of seronegative MG. Our findings suggest that tacrolimus therapy is a safe and effective option for the treatment of juvenile seronegative MG.

IgG-specific cell-based assay detects potentially pathogenic MuSK-Abs in seronegative MG

Objective:To increase the detection of MuSK-Abs using a CBA and test their pathogenicity.Methods:Sera from 69 MuSK-RIA–positive patients with myasthenia gravis (MG) (Definite MuSK-MG), 169 patients negative for MuSK-RIA and AChR-RIA (seronegative MG, SNMG), 35 healthy individuals (healthy controls, HCs), and 16 NMDA receptor-Ab–positive (NMDAR-Ab) disease controls were tested for binding to MuSK on a CBA using different secondary antibodies.Results:Initially, in addition to 18% of SNMG sera, 11% of HC and 19% of NMDAR-Ab sera showed positive binding to MuSK-transfected cells; this low specificity was due to anti-IgG(H+L) detection of IgM bound nonspecifically to MuSK. Using an IgG Fc gamma-specific secondary antibody, MuSK-Abs were detected by CBA in 68/69 (99%) of Definite MuSK-MG, 0/35 HCs, 0/16 NMDAR-Ab, and 14/169 (8%) of SNMG sera, providing increased sensitivity with high specificity. The RIA-negative, CBA-positive MuSK-IgG sera, but not IgM-MuSK–binding sera, reduced agrin-induced AChR clustering in C2C12 myotubes, qualitatively similar to RIA-positive MuSK-Abs.Conclusions:An IgG-specific MuSK-CBA can reliably detect IgG MuSK-Abs and increase sensitivity. In the MuSK-CBA, IgG specificity is essential. The positive sera demonstrated pathogenic potential in the in vitro AChR-clustering assay, although less effective than Definite MuSK-MG sera, and the patients had less severe clinical disease. Use of IgG-specific secondary antibodies may improve the results of other antibody tests.Classification of evidence:This study provides Class III evidence that an IgG-specific MuSK-CBA identifies patients with MG.