New diagnosis of myasthenia gravis in the third trimester – A case report

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Myasthenia gravis (MG) is an acquired autoimmune disorder of the neuromuscular junction with an annual incidence rate of 2 to 21 per million. A 25-year-old primiparous woman with no significant medical history presented for a routine antenatal appointment at 37weeks of gestation. She reported a two-week history of transient diplopia and a five-month history of fluctuating weakness in her proximal limbs. Pertinent neurological exam findings included right upper limb flaccidity, and bilateral upper and lower limb weakness more pronounced in the upper limbs and in proximal muscle groups. Cranial nerves III, IV and VI showed mild restriction in all directions, with diplopia in horizontal and downwards gaze. Following one week of investigations, including spirometry, magnetic resonance imaging of brain and spine, and needle electromyography, she was diagnosed with MuSK (anti-muscle-specific tyrosine kinase antibodies) associated myasthenia gravis. Potential complications in this context included myasthenic crisis, delivery complications, and transient neonatal myasthenia gravis. She was initially treated with 5days of plasmapheresis and prednisone. She proceeded to have an elective caesarean section for unstable lie at 39weeks of gestation under combined spinal/epidural anaesthesia without complications. The baby boy was born in good health, was monitored over four days and did not display signs of myasthenia gravis. This case outlines the rare occurrence of newly diagnosed myasthenia gravis in pregnancy, the complexities of management, and need for early multidisciplinary care.