Lower Urinary Tract Symptoms in Myasthenia Gravis

Myasthenia gravis and independent risk factors for recurrent infection: a retrospective cohort study

BACKGROUND

Approximately 10% to 20% of myasthenia gravis (MG) patients have experienced a myasthenic crisis (MC), which contributes to morbidity and mortality. MC triggered by infection is associated with poor outcomes. However, there is a lack of prognostic factors that clinicians can utilize to target interventions for preventing recurrent infection-triggered MC. This study aimed to characterize clinical manifestations, comorbidities, and biochemical profiles associated with recurrent infection-triggered MC in MG patients.

METHODS

This retrospective study included 272 MG patients hospitalized with an infection requiring at least 3 days of antibiotics from January 2001 to December 2019. Patients were further stratified into non-recurrent or recurrent infection groups. Clinical features such as gender, age, concomitant diseases, acetylcholine receptor antibodies and biochemical data (including electrolytes and coagulants), muscle strength of pelvic and shoulder girdle, bulbar and respiratory function, management with an endotracheal tube, Foley catheter, or plasmapheresis, duration of hospitalization, and culture pathogens were recorded.

RESULTS

The recurrent infection group was significantly older than the non-recurrent group (median age, 58.5 versus 52.0 years). Pneumonia was the most common infection and Klebsiella pneumoniae was the most common pathogen. The presence of concomitant diabetes mellitus, activated partial thromboplastin time prolongation, the duration of hospitalization, and hypomagnesaemia were independently associated with recurrent infection. The presence of deep vein thrombosis, thymic cancer, and electrolyte imbalances i.e., hypokalemia, and hypoalbuminemia were significantly associated with a risk for infection. The influence of endotracheal intubation, anemia, and plasmapheresis during hospitalization were inconsistent.

CONCLUSIONS

The independent risk factors for recurrent infections in MG patients identified in this study include the presence of concomitant diabetes mellitus, hypomagnesaemia, activated partial thromboplastin time prolongation, and longer duration of hospitalization, highlighting the need for targeted interventions to prevent recurrent infections in this population. Further research and prospective studies are warranted to validate these findings and refine interventions for optimizing patient care.

Development and characterization of agonistic antibodies targeting the Ig-like 1 domain of MuSK

Muscle-specific kinase (MuSK) is crucial for acetylcholine receptor (AChR) clustering and thereby neuromuscular junction (NMJ) function. NMJ dysfunction is a hallmark of several neuromuscular diseases, including MuSK myasthenia gravis. Aiming to restore NMJ function, we generated several agonist monoclonal antibodies targeting the MuSK Ig-like 1 domain. These activated MuSK and induced AChR clustering in cultured myotubes. The most potent agonists partially rescued myasthenic effects of MuSK myasthenia gravis patient IgG autoantibodies in vitro. In an IgG4 passive transfer MuSK myasthenia model in NOD/SCID mice, MuSK agonists caused accelerated weight loss and no rescue of myasthenic features. The MuSK Ig-like 1 domain agonists unexpectedly caused sudden death in a large proportion of male C57BL/6 mice (but not female or NOD/SCID mice), likely caused by a urologic syndrome. In conclusion, these agonists rescued pathogenic effects in myasthenia models in vitro, but not in vivo. The sudden death in male mice of one of the tested mouse strains revealed an unexpected and unexplained role for MuSK outside skeletal muscle, thereby hampering further (pre-) clinical development of these clones. Future research should investigate whether other Ig-like 1 domain MuSK antibodies, binding different epitopes, do hold a safe therapeutic promise.

Urinary incontinence as a possible signal of neuromuscular toxicity during immune checkpoint inhibitor treatment: Case report and retrospective pharmacovigilance study

Background

Immune checkpoint inhibitors (ICIs) are associated with different immune-related adverse events (irAEs), but there is limited evidence regarding the association between urinary incontinence and ICIs.

Methods

We described the case of a patient experiencing urinary incontinence who later experienced a series of irAEs such as myocarditis, myositis, and neurologic diseases while on ICI treatment in our hospital. In addition, we queried the Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) from the third quarter of 2010 to the third quarter of 2020 to perform a retrospective study to characterize the clinical features of urinary incontinence associated with ICIs.

Result

In the FAERS study, 59 cases of ICI-related urinary incontinence were retrieved, and approximately 32.2% of the cases were fatal. Combination therapy with nervous system drugs and age >80 years old were the significant risk factors for fatal outcomes. Among these cases of ICI-related urinary incontinence, 40.7% (n = 24) occurred concomitantly with other adverse events, especially, neurological (fifteen cases), cardiovascular (seven cases), musculoskeletal (six cases), and urological disorders (five cases). Five cases had an overlapping syndrome similar to our case report, including one case of myasthenia gravis with myocarditis and another of myasthenic syndrome with polymyositis.

Conclusion

ICI-related urinary incontinence might be a signal of fatal neuromuscular irAEs, especially when it occurs concomitantly with ICI-associated neuromuscular–cardiovascular syndrome. Clinicians should be aware of the occurrence of urinary incontinence to identify potentially lethal irAEs in the early phase.