The features of myasthenia gravis with autoantibodies to MuSK

Abstract

Objectives: To determine if myasthenia gravis (MG) with antibodies to MuSK is a distinct subgroup of seronegative MG. Methods: We assayed antibodies to muscle specific tyrosine kinase (MuSK) in 55 MG patients who had no antibodies to acetylcholine receptors and looked for the specific phenotype, comparing clinical features of anti-MuSK positive and anti-MuSK negative MG patients. Results: MG with anti-MuSK antibodies was characterised by a striking prevalence of female patients (15 women, two men). Age at onset ranged from 22 to 52 years, with 70.6% of patients presenting at ,40 years of age. The majority of patients (82.4%) had prevalent involvement of facial and bulbar muscles. One third of them did not respond well to anticholinesterase drugs. Steroid immunosuppression was effective in eight patients (44.4%). Nine patients underwent thymectomy; six of these had no thymus pathology, while three had a hyperplastic thymus. At the end of the observation period, six (35.3%) patients were in remission, five (29.4%) improved, four (23.6%) did not change, and two (11.7%) had died. Conclusions: MG patients with antibodies to MuSK have characteristic clinical features that are different from features of the remaining seronegative MG patients. This emphasises the predictive value of antiMuSK antibody analysis in seronegative MG patients.

Myasthenia gravis at Ouagadougou (Burkina Faso): about 14 cases

“…Approximately 40% of MG patients without AChR antibodies have MuSK antibodies. They are mostly young women [46], with severe clinical symptoms, with facial, bulbar and respiratory muscles symptoms, but rarely with ocular symptoms. Muscular atrophy is common in these patients [47].…”

Myasthenia Gravis with Anti-MuSK Antibodies: Clinical Features and Histopathological Changes

“…MG with MuSK-Ab is responsive to standard therapy, but needs higher drug dosages than MG AChR-Ab positive [19], MuSK-positive patients frequently develop hypersensitivity to anticholinesterase drugs [15]. Instead, seronegative MG without MuSK-Ab seems to have a similar or less severe clinical course than seropositive ones and a similar response to pharmacological treatment [20].…”

“…Mean time to diagnosis is often over 1 year [13; 14]. The diagnostic value of neostigmine or edrophonium test and repetitive stimulation is low [15], while single fibre EMG has very high sensitivity.…”

The role of regulatory T cells, interleukin-10 and in vivo scintigraphy in autoimmune and idiopathic diseases – Therapeutic perspectives and prognosis

“…Immunized rabbits had fallen ears and palpebral ptosis (drooping eyelid) with improvement at rest and worsening with exercise, infections and emotional stress. 48 The role of these antibodies in the etiology of MG was clearly established in the 1970s, when plasmapheresis proved to be effective in the removal of antibodies and consequent functional improvement for more than 2 months. 49,50 Well-established anatomical changes were also observed, including increased neuromuscular junction size and decreased post-synaptic membrane length.…”

“…Other important observations have been reported on the role of autologous antibodies in MG, since approximately 50% of patients with the disease without Ach anti-receptor antibodies have antibodies against a muscle membrane enzyme called muscle-specific tyrosine kinase (anti-Musk). Lavrnic et al 48 analyzed 17 patients with this condition, observing a higher prevalence of women, predominant facial and bulbar involvement and refractoriness to anticholinesterase compounds. Because it is an autoimmune disease, other conditions of the same nature may coexist in a patient with a diagnosis of MG, and should be screened rationally, especially hypothyroidism, hyperthyroidism and thymus disease.…”