Analysis of clinical features of myasthenia gravis complicated with hyperthyroidism

Objectives: To investigate the clinical features of patients with myasthenia gravis complicated with and without hyperthyroidism. Methods: A total of 2083 patients with myasthenia gravis (MG) admitted in Center of Treatment of Myasthenia Gravis Hebei Province between January 2013 and July 2020 were retrospectively analyzed and divided into two groups: Group-A and Group-B, with 108 MG patients complicated with hyperthyroidism in Group-A and 1975 MG patients without thyroid disease in Group-B. The age of onset, gender, Osserman classification, acetylcholine receptor antibody and thymus status of the two groups were analyzed in the two groups. Independent-sample t test was used for intra-group comparison, and χ2 test was utilized for comparison of enumeration data. P<0.05 indicates a statistically significant difference. Results: The age of onset in Group-A was significantly lower than that in Group-B (p=0.000), the number of female patients was significantly higher than that in Group-B (p=0.037), and the level of Achrabs titer was significantly lower than that in Group-B (p=0.000). The incidence of thymoma in Group-A was significantly lower than that in Group-B (p=0.012), while the incidence of thymic hyperplasia was significantly higher than that in Group-B (p=0.000). Conclusion: Patients with MG complicated with hyperthyroidism are mainly female, with a lower age of onset, a lower level of acetylcholine receptor antibody, a lower incidence of thymoma, and a higher incidence of thymic hyperplasia. The clinical features of such patients are remarkably different from those of MG without thyroid disease. doi: https://doi.org/10.12669/pjms.38.3.4656 How to cite this:Wang Y, Qi G, Yang Y. Analysis of clinical features of myasthenia gravis complicated with hyperthyroidism. Pak J Med Sci. 2022;38(3):---------. doi: https://doi.org/10.12669/pjms.38.3.4656 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Ancestral acetylcholine receptor β-subunit forms homopentamers that prime before opening spontaneously

Human adult muscle-type acetylcholine receptors are heteropentameric ion channels formed from two α-subunits, and one each of the β-, δ-, and ϵ- subunits. To form functional channels, the subunits must assemble with one another in a precise stoichiometry and arrangement. Despite being different, the four subunits share a common ancestor that is presumed to have formed homopentamers. The extent to which the properties of the modern-day receptor result from its subunit complexity is unknown. Here we show that a reconstructed ancestral muscle-type β-subunit can form homopentameric ion channels. These homopentamers open spontaneously and display single-channel hallmarks of muscle type acetylcholine receptor activity. Our findings demonstrate that signature features of muscle-type acetylcholine receptor function are independent of agonist, and do not necessitate the complex heteropentameric architecture of the modern-day receptor.

Loss of α-9 Nicotinic Acetylcholine Receptor Subunit Predominantly Results in Impaired Postural Stability Rather Than Gaze Stability

The functional role of the mammalian efferent vestibular system (EVS) is not fully understood. One proposal is that the mammalian EVS plays a role in the long-term calibration of central vestibular pathways, for example during development. Here to test this possibility, we studied vestibular function in mice lacking a functional α9 subunit of the nicotinic acetylcholine receptor (nAChR) gene family, which mediates efferent activation of the vestibular periphery. We focused on an α9 (−/−) model with a deletion in exons 1 and 2. First, we quantified gaze stability by testing vestibulo-ocular reflex (VOR, 0.2–3 Hz) responses of both α9 (−/−) mouse models in dark and light conditions. VOR gains and phases were comparable for both α9 (−/−) mutants and wild-type controls. Second, we confirmed the lack of an effect from the α9 (−/−) mutation on central visuo-motor pathways/eye movement pathways via analyses of the optokinetic reflex (OKR) and quick phases of the VOR. We found no differences between α9 (−/−) mutants and wild-type controls. Third and finally, we investigated postural abilities during instrumented rotarod and balance beam tasks. Head movements were quantified using a 6D microelectromechanical systems (MEMS) module fixed to the mouse’s head. Compared to wild-type controls, we found head movements were strikingly altered in α9 (−/−) mice, most notably in the pitch axis. We confirmed these later results in another α9 (−/−) model, with a deletion in the exon 4 region. Overall, we conclude that the absence of the α9 subunit of nAChRs predominately results in an impairment of posture rather than gaze.

Myasthenia gravis associated with a pelvic follicular lymphoma

An 81-year-old woman presented with neck weakness, dysarthria, dysphasia and left-sided ptosis. Myasthenia gravis (MG) was strongly suspected. Voltage gated calcium channel (VGCC) antibodies, associated with Lambert-Eaton myasthenic syndrome (LEMS), were negative. Acetylcholine receptor (AChR) antibody level was 536 nmol/L and diagnosis of MG was confirmed. Imaging revealed a pelvic mass and subsequent biopsy confirmed a pelvic follicular lymphoma. Our searches revealed this to be the first documented case of MG associated with a pelvic follicular lymphoma. She underwent radiotherapy to treat the lymphoma and received both pyridostigmine and immunosuppression to treat the MG. Her AChR antibody level decreased to 38 nmol/L and her MG symptoms resolved aside from head drop which is continuing to improve. Her lymphoma is now in remission. We have presented a case with a successful outcome, which highlights the importance of screening for lymphoma and thymoma in new presentations of MG.