Laboratory Investigation of Hybrid IgG4 k/λ in MuSK Positive Myasthenia Gravis

An unusual initiation of an ocular form of MuSK-positive myasthenia gravis after magnesium administration: a rare case report

Introduction and importance

The primary clinical symptom in people with myasthenia gravis (MG) is muscle weakness that gets worse with activity and gets better with rest; often, the first symptoms are ocular ones, such as ptosis and double vision. On the other hand, individuals with anti-muscle-specific tyrosine kinase may present with unusual symptoms. Nonetheless, it is hypothesized that muscle-specific tyrosine kinase antibodies may be present when no antibodies are present, along with bulbar and respiratory symptoms.

Case presentation

A 26-year-old pregnant patient was referred to the Neurology Department after experiencing tongue enlargement. A neuro-ophthalmic assessment revealed ptosis with lateral diplopia in the right eye, bulbar palsy, facial weakness, weakness in the palate and pharyngeal reflex, dizziness, and hearing loss in her right ear. The patient was given magnesium sulfate for 2 days since pre-eclampsia was suspected; however, this treatment exacerbated the development of symptoms and was discontinued. Her MG symptoms gradually improved after starting medication. Nonetheless, bilateral weakness in the neck and limb flexion persisted. Following a few days of therapy, there were no indications of diplopia, swallowing was normal, and the muscular weakness was somewhat improved.

Clinical discussion

The patient was put on drug treatment for MG (predlon 60 mg daily, amioran 50 mg twice daily, and mistenon).

Conclusion

Treating severe MG patients with a customized approach aims to manage their symptoms and improve their quality of life. Reduce muscle weakness, eradicate circulating antibodies, and suppress the abnormal immunological response. Minimizing side effects while attaining ideal symptom control is the ultimate objective.

Advancements in Mid-Infrared spectroscopy of extracellular vesicles

Extracellular vesicles (EVs) are lipid vesicles secreted by all cells into the extracellular space and act as nanosized biological messengers among cells. They carry a specific molecular cargo, composed of lipids, proteins, nucleic acids, and carbohydrates, which reflects the state of their parent cells. Due to their remarkable structural and compositional heterogeneity, characterizing EVs, particularly from a biochemical perspective, presents complex challenges. In this context, mid-infrared (IR) spectroscopy is emerging as a valuable tool, providing researchers with a comprehensive and label-free spectral fingerprint of EVs in terms of their specific molecular content. This review aims to provide an up-to-date critical overview of the major advancements in mid-IR spectroscopy of extracellular vesicles, encompassing both fundamental and applied research achievements. We also systematically emphasize the new possibilities offered by the integration of emerging cutting-edge IR technologies, such as tip-enhanced and surface-enhanced spectroscopy approaches, along with the growing use of machine learning for data analysis and spectral interpretation. Additionally, to assist researchers in navigating this intricate subject, our manuscript includes a wide and detailed collection of the spectral peaks that have been assigned to EV molecular constituents up to now in the literature.

Enrichment of serum IgG4 in MuSK myasthenia gravis patients

Muscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disease belonging to a growing group of IgG4 autoimmune diseases (IgG4-AIDs), in which the majority of pathogenic autoantibodies are of the IgG4 subclass. The more prevalent form of MG with acetylcholine receptor (AChR) antibodies is caused by IgG1-3 autoantibodies. A dominant role for IgG4 in autoimmune disease is intriguing due to its anti-inflammatory characteristics. It is unclear why MuSK autoantibodies are predominantly IgG4. We hypothesized that MuSK MG patients have a general predisposition to generate IgG4 responses, therefore resulting in high levels of circulating IgG4. To investigate this, we quantified serum Ig isotypes and IgG subclasses using nephelometric and turbidimetric assays in MuSK MG and AChR MG patients not under influence of immunosuppressive treatment. Absolute serum IgG1 was increased in both MuSK and AChR MG patients compared to healthy donors. In addition, only MuSK MG patients on average had significantly increased and enriched serum IgG4. Although more MuSK MG patients had elevated serum IgG4, for most the IgG4 serum levels fell within the normal range. Correlation analyses suggest MuSK-specific antibodies do not solely explain the variation in IgG4 levels. In conclusion, although serum IgG4 levels are slightly increased, the levels do not support ubiquitous IgG4 responses in MuSK MG patients as the underlying cause of dominant IgG4 MuSK antibodies.

Biomarkers in Rare Diseases 2.0

It is estimated that there are over 7000 rare diseases, collectively affecting more than 350 million individuals worldwide [...].