Unmasking Myasthenia Gravis: Acute Respiratory Failure in an Adolescent

Abstract Introduction: Most patients with Myasthenia Gravis (MG) experience respiratory symptoms only in the later stages of the disease. It is rare for respiratory failure to be the sole initial symptom in patients with MG. We present a case of a 17-year-old female who was admitted to our hospital with acute-onset respiratory failure, which turned out to be the first manifestation of MG. Case Description: A 17-year-old female with a medical history of HbSC, sleep-disordered breathing, and moderate persistent asthma was transferred to our center from an outside hospital due to altered mental status. Upon arrival at the Pediatric Intensive Care Unit, the patient was intubated due to acute hypercapnic respiratory failure. A detailed assessment revealed a three-year history of progressive symptoms, including coordination difficulties, fatigue, dysarthria, dysphagia, ptosis, and double vision. She also had a history of sleep-disordered breathing, including snoring, shallow breathing, and ineffective coughing, and was awaiting sleep study. Notably, she had experienced significant weight loss over the past year, likely due to feeding difficulties. MRI of the brain and spine was normal. Negative inspiratory force (NIF) measurements were low (<15), suggesting respiratory muscle weakness. Attempts to extubate the patient on the fourth day after admission led to desaturation and hypercapnia, requiring re-intubation. Ultimately, she was successfully extubated to non-invasive ventilation with a mask interface. Given her progressive bulbar symptoms, neurology was consulted. Testing revealed the presence of anti-MuSK antibodies, confirming the diagnosis of myasthenia gravis. The patient underwent five days of apheresis and two days of IVIG infusions, followed by initiation of pyridostigmine and monthly rituximab infusions (four doses). After treatment, she was discharged home on daily prednisolone, pyridostigmine, and nighttime non-invasive ventilatory support. During follow-up, the patient showed gradual improvement, with near-normal inspiratory and expiratory muscle strength. Sleep study results were normal during follow up Discussion: Juvenile myasthenia gravis (JMG) is a rare condition in children and should be considered in any child presenting with fluctuating weakness and fatigue. Physicians must consider neurological causes when cardiac or respiratory conditions cannot explain dyspnea. Myasthenic crisis should be suspected in children with progressive neurological weakness that rapidly involves bulbar and respiratory muscles. Early recognition and prompt treatment can be lifesaving. JMG accounts for approximately 10-15% of all MG cases, with a higher incidence among African-American females. Patients with anti-MuSK antibody-positive MG often present atypically with respiratory muscle weakness rather than ocular weakness usually seen in anti-AChR antibody-positive cases.