Receptor Tyrosine Kinase Antibodies Research Articles

Differential Expression of miRNA in the Peripheral Blood Mononuclear Cells in Myasthenia Gravis with Muscle-Specific Receptor Tyrosine Kinase Antibodies.

To determine if differential profile of miRNAs in peripheral blood mononuclear cells (PBMCs) could be identified in muscle-specific receptor tyrosine kinase antibody positive myasthenia gravis (MuSK-MG) and linked to disease stage, a case-control method was used to compare the difference in miRNA expression profiles of PBMCs using next generation sequencing (NGS) in MuSK-MG patients and healthy controls (HCs). Six significant miRNAs from the discovery set were then validated using RT-qPCR in 11 MuSK-MG patients and 10 HCs. A unique miRNA prediction algorithm was used to predict the target genes of differentially expressed miRNAs and a network of miRNA gene pathways. Compared with HCs, 101 differentially expressed miRNAs were screened in MuSK-MG, of which 5 miRNAs were upregulated, and 96 miRNAs were downregulated. The top six differentially expressed molecules were selected for verification; four of them (miR-340-5p, miR-106b-5p, miR-27a-3p, and miR-15a-3p) were significantly different. The network analysis of miRNA gene pathways revealed that differentially expressed miRNAs were involved in a complex set of biological processes. Clinically, the four miRNAs that were validated are not correlated to MuSK antibody titers and quantitative myasthenia gravis score. Four miRNAs that were validated in this study have specificity to distinguish MuSK-MG from HCs.

P48 A case of myasthenia gravis presenting to the rheumatology clinic

Abstract Background A 32-year-old Lithuanian lady, with a 6-year history of undifferentiated inflammatory arthritis and autoimmune neutropenia, contacted her rheumatologist reporting a constellation of new symptoms. This began with a month’s history of facial weakness and slurred speech. She progressively experienced nasal regurgitation on drinking fluids, reduced exercise tolerance, as well as difficulty chewing, swallowing, and coughing. Her symptoms initially came on in the evening but subsequently appeared earlier in the day. There were no symptoms suggestive of infection. Her arthritis had been well-controlled on hydroxychloroquine and sulfasalazine. She was previously on methotrexate, but this was discontinued due to plans to conceive. Methods Clinical examination during an urgent outpatient review yielded dysphonic, mildly dysarthric speech. Extraocular movements were normal with no ophthalmoplegia. There was mild lower motor neurone facial weakness and an absent gag reflex. She demonstrated fatiguability on repetitive tongue movements and arm abduction. There were no upper motor neurone or cerebellar signs. Blood tests showed normal inflammatory markers, full blood count, creatine kinase, immunoglobulins, liver, and renal profile. Her anti-nuclear antibody titre, previously weakly positive at time of diagnosis of inflammatory arthritis, was 1:1280 (homogenous). Anti-cyclic citrullinated peptide, rheumatoid factor, and extractable nuclear antigens were negative. Virology screen was unremarkable. Neurology input was sought. Anti-acetylcholine receptor antibody was positive at 5.2nmol/L (normal range 0-0.45nmol/L), anti-muscle specific receptor tyrosine kinase antibody was negative. Nerve conduction studies showed decremental response on repetitive stimulation of her left nasalis, consistent with a post-synaptic neuromuscular junction transmission disorder. There was no evidence of myopathy. Results The clinical symptoms and the investigations led to the diagnosis of myasthenia gravis with predominant bulbar features. Computed tomography showed no evidence of thymoma or thymic hyperplasia. Magnetic resonance imaging of the brain showed no evidence of space-occupying lesion or brainstem abnormality. She initially received pyridostigmine 30mg three times daily with propantheline cover to which she reported a good response. A viral illness led to deterioration of her symptoms of breathlessness and worsening dysphagia resulting in a hospital admission. She received intravenous immunoglobulins 20g daily for three days. Hydroxychloroquine and sulfasalazine were replaced with methotrexate 15mg weekly. She now remains on pyridostigmine 90mg five times daily and 10mg prednisolone daily with good effect. Conclusion Myasthenia gravis is a rare condition (prevalence of 10-20 per 100,000 in the United Kingdom). However, this occurs at a higher prevalence in autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. This case illustrates the importance of remaining vigilant about symptoms which patients may disclose in the rheumatology clinic which may not fit with their known diagnosis. Her previous use of methotrexate for her arthritis could have masked her myasthenic symptoms which became apparent after the drug was stopped for a prolonged period. Disclosures S. Yeoh None. S. Salam None. G. Christofi None. V. Morris None.

Simultaneous Presence of Acetylcholine Receptor and Muscle Specific Tyrosine Kinase Antibodies in Myasthenia Gravis

Myasthenia gravis (MG) is known as an autoimmune disorder which affects transmission in neuromuscular junction. The serologic tests used for diagnosis include acetylcholine receptor and muscle specific receptor tyrosine kinase antibodies. Studies often have reported that patients with formal antibody are negative for the latter one. However, very limited studies have reported positive anti-muscle specific receptor tyrosine kinase antibody in a small percentage of patients with acetylcholine receptor antibody. Here, we reported a young woman who was diagnosed with MG and had a rapid and progressive course of the disease. She was seropositive for both acetylcholine receptor and muscle-specific receptor tyrosine kinase antibodies simultaneously. However, she discharged from the hospital with good condition after treatment.

Usefulness of the video fluoroscopic examination of swallowing in a patient with anti–muscle–specific receptor tyrosine kinase antibody–positive myasthenia gravis

Usefulness of the video fluoroscopic examination of swallowing in a patient with anti–muscle–specific receptor tyrosine kinase antibody–positive myasthenia gravis

Incidence of Autoimmune Myasthenia Gravis in a Health Maintenance Organization in Buenos Aires, Argentina

Background: Different epidemiological studies, especially in Europe, have estimated the incidence density of myasthenia gravis (MG) to range between 1.7 and 21.3/1,000,000/person-year; however, data from regions such as Latin America are scarce. This study is aimed at estimating the incidence and prevalence of acquired MG in Buenos Aires, Argentina. Methods: The study population comprised of affiliates of the Italian Hospital Medical Care Program, a prepaid health maintenance organization located in Buenos Aires. The evaluation method for case detection included a retrospective search from January 1, 2006, through December 31, 2012. Results: Of the 60 cases identified, 36 (60%) were females. The median age at diagnosis was 69 years (IQR 51.5-79). The mean age at diagnosis was 63.3 years (SD ±20). A total of 28 patients (46.7%) had generalized MG and 32 had ocular MG (53.3%). Thirty five patients (58.3%) had acetylcholine receptor antibodies and 2 (3.3%) had muscle-specific receptor tyrosine kinase antibodies. The crude incidence density (ID) of MG was 61.33 per 1,000,000 person-years (95% CI 47.62-79.99). The adjusted ID for the Argentinean population was 38.8 per 1,000,000 person-years (95% CI 27.09-50.51) and for the Buenos Aires population was 47.49 (95% CI 34.73-60.25). Conclusions: The results obtained are similar to those published for other geographical areas.

Anti‐LRP4 autoantibodies in Chinese patients with myasthenia gravis

We assessed antibodies against low-density lipoprotein receptor-related protein 4 (LRP4-Ab) in a Chinese population with myasthenia gravis (MG). Serum samples from 116 patients and 80 controls were collected. Acetylcholine receptor antibodies(AChR-Ab) and muscle-specific receptor tyrosine kinase antibodies (MuSK-Ab) were tested using an enzyme-linked immune absorption assay, and LRP4-Ab was identified using a cell-based assay. MG patients with neither AChR-Ab nor MuSK-Ab were defined as double-seronegative MG (dSN-MG). Two of 116 (1.7%) of all patients and 2 of 50 (1%) dSN-MG patients were positive for LRP4-Ab. These 2 patients had ocular MG. Following treatment with acetylcholinesterase inhibitor and prednisone, both achieved full remission. This study shows that LRP4-Ab is a pathogenic antibody in MG. LRP4-MG seems to be characterized by mild disease severity and favorable therapeutic effect in contrast with other types of MG. Muscle Nerve 56: 938-942, 2017.

Sunitinib suppress neuroblastoma growth through degradation of MYCN and inhibition of angiogenesis.

Neuroblastoma, a tumor of the peripheral sympathetic nervous system, is the most common and deadly extracranial tumor of childhood. The majority of high-risk neuroblastoma exhibit amplification of the MYCN proto-oncogene and increased neoangiogenesis. Both MYCN protein stabilization and angiogenesis are regulated by signaling through receptor tyrosine kinases (RTKs). Therefore, inhibitors of RTKs have a potential as a treatment option for high-risk neuroblastoma. We used receptor tyrosine kinase antibody arrays to profile the activity of membrane-bound RTKs in neuroblastoma and found the multi-RTK inhibitor sunitinib to tailor the activation of RTKs in neuroblastoma cells. Sunitinib inhibited several RTKs and demonstrated potent antitumor activity on neuroblastoma cells, through induction of apoptosis and cell cycle arrest. Treatment with sunitinib decreased MYCN protein levels by inhibition of PI3K/AKT signaling and GSK3β. This effect correlates with a decrease in VEGF secretion in neuroblastoma cells with MYCN amplification. Sunitinib significantly inhibited the growth of established, subcutaneous MYCN-amplified neuroblastoma xenografts in nude mice and demonstrated an anti-angiogenic effect in vivo with a reduction of tumor vasculature and a decrease of MYCN expression. These results suggest that sunitinib should be tested as a treatment option for high risk neuroblastoma patients.

Critical vocal cord abductor paralysis as an emergency in myasthenia gravis

A 78-year-old woman was admitted for sudden-onset dyspnea, presenting with hypoxemia, stridor and pooling of saliva in the pharynx. One month earlier, she had complained of dysphagia and had been diagnosed with myasthenia gravis (MG) based on weakness of the proximal muscles, decremental response in repetitive nerve stimulation and positive anti-acetylcholine receptor antibodies (Myasthenia Gravis Foundation of America [MGFA] class IIb). Laryngoscopy disclosed severe bilateral vocal cord abductor paralysis (VCAP), which was improved to one-third of the maximum abduction by edrophonium injection (Fig. 1a, b). An emergency tracheostomy was required to avoid suffocation (MGFA class V). Immunosuppressive treatment improved symptoms including VCAP (Fig. 1c). A thymectomy was carried out and the involuted thymus was found. VCAP, a rare complication of MG, can be the first and sole manifestation of the disease.1 VCAP also occurs in patients with anti-muscle-specific receptor tyrosine kinase antibodies.2 When neurologists encounter dyspnea in MG, not only respiratory muscle weakness, but also VCAP should be considered, and indications of tracheostomy must be assessed immediately by laryngoscopy using edrophonium. The authors declare no conflicts of interests with respect to this article.

Perioperative Therapeutic Plasmapheresis

Perioperative Therapeutic Plasmapheresis

胸腺腫を合併した抗筋特異的受容体チロシンキナーゼ抗体陽性重症筋無力症の1例

We report a 60-year-old male with thymoma-associated myasthenia gravis with anti-MuSK antibodies. In October 2010, he had diplopia, ptosis, and dysphagia. He was diagnosed to have MG in February 2011. The neurological examination disclosed external ophthalmoplegia, bilateral ptosis, mild dysphagia, and fatigability. Repetitive nerve stimulation of the right facial nerve showed CMAP decrement greater than 10%. Patients showed an improvement in ptosis after administration of edrophonium.Anti-acetylcholine receptor antibody was negative, and anti-muscle specific receptor tyrosine kinase antibody was 66.8 nmol/l (cut-off value: 0.05 nmol/l). Prednisolone (50 mg every other day) were started. Contrast-enhanced chest MRI showed a mediastinal mass suggestive of thymoma. Extended thymectomy was performed in March 2011. Histological examination disclosed a type B1 thymoma. After resection of the tumor, the symptoms of MG improved with prednisolone (100 mg every other day). This is a rare case of MG with anti-MuSK antibodies and thymoma, which has been reported previously only in 2 cases.

Treatment of anti-MuSK antibody positive myasthenia gravis

The authors report the case of a 27-year-old woman with muscle-specific receptor tyrosine kinase antibody positive myasthenia with predominantly ocular and bulbar symptoms. Both edrophonium and low dose (4×30 mg/day) pyridostigmin resulted in cholinergic side effects including fasciculation mainly in the facial and neck muscles, and excessive salivation. The patient responded well to a relatively high dose of chronic corticosteroid treatment (methyprednisolone 64mg/day), but the decrease of the corticosteroid dose below 16 mg/day induced exacerbation of the clinical symptoms. Immunosuppression with azathioprine and methotrexate failed to maintain the clinical improvement. However, plasma exchange was always very effective, and all clinical symptoms improved significantly. The authors conclude that patients with muscle-specific receptor tyrosine kinase antibody positive myasthenia gravis should have an individual treatment protocol differing from those used in patients who do not have this antibody but are positive for acetylcholine-receptor antibody. Identification of the pathogenic antibody in the early stage of myasthenia gravis may help to develop the optimal, individualized treatment strategy, to avoid severe side effects, and to achieve fast improvement. Orv. Hetil., 2011, 152, 1586–1589.

Prolonged Improvement After Rituximab: Two Cases of Resistant Muscle-Specific Receptor Tyrosine Kinase + Myasthenia Gravis

Forty percent to 50% of acetylcholine receptor antibody-seronegative patients with myasthenia gravis have muscle-specific receptor tyrosine kinase antibodies. Many muscle-specific receptor tyrosine kinase + myasthenia gravis patients remain refractory with conventional therapies. Rituximab is an anti-CD20 monoclonal antibody used in refractory B-cell disorders. Currently there is no standard dosing schedule for rituximab. We present two muscle-specific receptor tyrosine kinase + myasthenia gravis patients clinically refractory to conventional therapy who, after a single course of rituximab, became asymptomatic and discontinued all medication.

Myasthenia gravis: diagnostic and management dilemmas.

This review focuses on the diagnostic tests that may help to confirm myasthenia in patients without acetylcholine receptor antibodies, including the newly discovered anti-muscle-specific receptor tyrosine kinase antibody and other investigations. We discuss management dilemmas, particularly those that revolve around treatments whose efficacy is questionable or unproved, such as thymectomy. We review the important issue of how treatments are assessed, and examine future treatment trial designs.