Myositis in H1N1 Infection Compounds to Myasthenic Crisis

Area of Science:

• Neurology
• Infectious Diseases
• Immunology

Background:

• Infection is a known precipitant of myasthenic crisis (MC) in myasthenia gravis (MG).
• Pneumonia and concurrent muscle involvement may exacerbate MC frequency and severity in MG patients.
• Influenza A (H1N1) infection presents a significant risk for MG patients, particularly those on immunosuppressive therapy.

Purpose of the Study:

• To report two cases of myasthenia gravis (MG) patients experiencing H1N1 infection.
• To identify key factors contributing to the deterioration and myasthenic crisis (MC) in these patients.
• To emphasize the importance of evaluating for myositis in MG patients with H1N1-associated pneumonia.

Main Methods:

• Case report of two myasthenia gravis (MG) patients diagnosed with H1N1 infection.
• Diagnostic confirmation of MG via neostigmine test, repetitive nerve stimulation, and anti-acetylcholine receptor antibody assays.
• H1N1 infection confirmed by nucleic acid detection; myositis assessed by creatinine kinase levels.

Main Results:

• One MG patient with H1N1, pneumonia, and myositis developed a severe myasthenic crisis (MC) requiring 10 days of mechanical ventilation.
• The second MG patient with H1N1 but without myositis did not experience MC and recovered fully within 6 days.
• Both patients were on prednisolone and azathioprine and had not received prior H1N1 vaccination.

Conclusions:

• Myositis, in addition to pneumonia, significantly increases the risk of myasthenic crisis (MC) in MG patients with H1N1 infection.
• Early detection and management of myositis are critical for improving outcomes in MG patients with H1N1.
• H1N1 vaccination may be beneficial for MG patients, especially those on immunosuppressive treatments.