Coexistence between myasthenia gravis and neuromyelitis optica: a case report
TL;DR
In patients with dual diagnosis and complications from chronic steroid use, such as the bilateral cataracts and retinitis seen in this case, the switch to highly specific monoclonal antibodies is essential to minimize systemic toxicity while maintaining strict disease control.
Abstract
Case Presentation: A 53-year-old woman was diagnosed with Myasthenia Gravis (MG) in 1999, confirmed by electromyography showing a 20% decremental response. Her family history was notable for a sister with Neuromyelitis Optica (NMO). For 19 years, the patient was managed with corticosteroids and intravenous immunoglobulin (IVIG) cycles, the last in 2016. Chronic steroid use led to bilateral cataracts and subsequent retinitis. In December 2023, she developed progressive tetraparesis and paresthesia, predominantly on the left side. Upon admission, she was conscious and oriented but bedridden. Physical examination revealed Grade I spastic tetraparesis (MRC scale), hyperreflexia with an expanded reflex zone in the lower limbs, and unsustained clonus. Laboratory findings included a positive ANA (1:320), positive Anti-AQP4, and negative Anti-AChR antibodies. Cerebrospinal fluid (CSF) analysis showed a protein level of 79 mg/dL. Spinal MRI revealed an extensive longitudinal lesion, fulfilling the International Panel for NMO Diagnosis (IPND) criteria. Treatment involved high-dose corticosteroids (40 mg/day) and the initiation of Ravulizumab. Discussion: Both NMO and MG are antibody-mediated autoimmune diseases. In NMO, IgG1 antibodies target aquaporin-4 (AQP4), while MG is primarily associated with IgG antibodies against the nicotinic acetylcholine receptor (AChR). Interestingly, at the time of NMO onset, the patient tested positive for Anti-AQP4 but negative for Anti-AChR, despite the previous MG diagnosis. This suggests a potential shift or inversely proportional relationship in antibody titers over time, where AQP4-IgG levels may rise significantly preceding NMO clinical manifestations. Although NMO is frequently associated with other autoimmune conditions, its coexistence with MG is uncommon, typically with MG as the primary diagnosis. The presence of NMO in a first-degree relative also underscores the importance of investigating genetic susceptibility. The Ravulizumab is a long-acting C5 inhibitor, representing a significant advancement in personalized medicine. Its engineered structure allows for a longer half-life compared to earlier C5 inhibitors, requiring infusions only every 8 weeks. In patients with dual diagnosis and complications from chronic steroid use, such as the bilateral cataracts and retinitis seen in this case, the switch to highly specific monoclonal antibodies is essential to minimize systemic toxicity while maintaining strict disease control. Final Comments: This case highlights the complexity of managing overlapping neuroimmunological disorders and the role of modern monoclonal antibodies, such as Ravulizumab, in specialized care.