Delayed diagnosis of distal myasthenia gravis: a case report

Myasthenia gravis, which initially presents with prominent distal muscle weakness, is rare and is referred to as distal myasthenia gravis. Despite its clinical significance, the diagnosis of distal myasthenia gravis is often delayed or missed owing to mild and atypical symptoms. We report the case of a 52-year-old ethnic Han woman who presented with task-related isolated transient right-hand weakness that began 15 years ago and lasted for 9 years without aggravation or improvement. In subsequent years, she developed right-hand stiffness with limited dexterity. More recently, this developed into bilateral hand weakness and simultaneous generalized weakness with ambulation, prompting suspicion of myasthenia gravis. Under Hertz repetitive nerve stimulation, the right facial nerve, right accessory nerve, right ulnar nerve, right radial nerve, and right median nerve showed decrements between 19.5% and 35.4%. Tests for anti-acetylcholine receptor antibodies were positive. The patient was diagnosed with distal myasthenia gravis, which evolved into generalized myasthenia gravis. Distal myasthenia gravis can present with isolated and transient hand weakness as a lone symptom, and can persist for years before typical myasthenia gravis symptoms appear. The inclusion of myasthenia gravis in the differential diagnosis is necessary in patients with isolated distal weakness.