Management of Lower Respiratory Tract Infection in Patients with Myasthenia Gravis

Immediate Risk Assessment and Hospital Admission

The European Respiratory Society identifies specific signs requiring immediate hospital admission, including temperature <35°C or ≥40°C, heart rate ≥125 beats/min, respiratory rate ≥30 breaths/min, cyanosis, blood pressure <90/60 mmHg, confusion, or altered mental status, in patients with myasthenia gravis and lower respiratory tract infection 1, 2
Presence of myasthenia gravis itself constitutes a neurological comorbidity requiring hospital referral for lower respiratory tract infection, according to the European Respiratory Society 1, 2

Pulmonary function testing with negative inspiratory force (NIF) and vital capacity (VC) should be performed to quantify respiratory muscle strength in patients with myasthenia gravis and lower respiratory tract infection 3
Arterial blood gases or pulse oximetry should be performed to assess for hypoxemia or hypercapnia, with hypoxemia defined as PaO₂ <60 mmHg or hypercapnia defined as PaCO₂ >50 mmHg, indicating severe disease 1, 4
Chest radiograph (posteroanterior and lateral) should be performed to assess for multilobar involvement, pleural effusion, or cavitation in patients with myasthenia gravis and lower respiratory tract infection 1, 4
Complete blood count, serum biochemistry (sodium, potassium, glucose, urea, creatinine) should be performed to assess for any underlying abnormalities 1
Sputum Gram stain and culture should be performed, with results only interpreted if >25 polymorphonuclear cells and <10 squamous epithelial cells per high-power field, to guide antibiotic therapy 5, 4
Blood cultures should be performed before antibiotic initiation to identify any potential bacterial pathogens 6

The American Society of Clinical Oncology (ASCO) guideline recommends reviewing and stopping medications with known risk of worsening myasthenia, including beta-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolide antibiotics, in patients with myasthenia gravis and lower respiratory tract infection 3
Second or third-generation cephalosporins, such as IV cefuroxime 750-1500 mg every 8 hours, IV ceftriaxone 1 g daily, or IV cefotaxime 1 g every 8 hours, should be used as first-line therapy for hospitalized patients with myasthenia gravis and lower respiratory tract infection 2, 6
Alternative therapy with IV aztreonam plus IV azithromycin may be necessary in severe allergy cases with close monitoring, despite the risk of worsening myasthenia gravis 6
Combination therapy with a second or third-generation cephalosporin plus a second-generation quinolone may be necessary in life-threatening situations with close monitoring, despite the risk of worsening myasthenia gravis 2
Treatment duration for uncomplicated bacterial lower respiratory tract infection should be 7-10 days 5

Pyridostigmine dosing should be started at 30 mg PO three times daily, gradually increased to maximum 120 mg four times daily based on symptoms, in patients with myasthenia gravis and lower respiratory tract infection 3
IVIG 2 g/kg IV over 5 days (0.4 g/kg/day) may be used as an alternative to plasmapheresis for myasthenic crisis, according to the American Society of Clinical Oncology (ASCO) guideline 3
Corticosteroids, such as prednisone 0.5 mg/kg orally daily, should be initiated or optimized in patients with myasthenia gravis and lower respiratory tract infection who develop signs of impending myasthenic crisis 3

Patients with myasthenia gravis and lower respiratory tract infection should be transferred to the ICU immediately if they develop respiratory rate >30 breaths/min, PaO₂/FiO₂ <250 mmHg, or need for mechanical ventilation, according to the European Respiratory Society and Praxis Medical Insights 1, 6, 7
Patients should also be transferred to the ICU if they develop progressive bulbar weakness with aspiration risk, declining NIF or VC on serial measurements, systolic blood pressure <90 mmHg or diastolic <60 mmHg, or altered mental status or confusion 3, 7

Daily assessments should include serial pulmonary function testing (NIF and VC), clinical evaluation for bulbar symptoms, respiratory rate, oxygen saturation, work of breathing, and response to antibiotic therapy, in patients with myasthenia gravis and lower respiratory tract infection 1, 3, 4
Fever should resolve within 48 hours of antibiotic therapy, and patients should be closely monitored for any signs of worsening myasthenia gravis or lower respiratory tract infection 4