What condition is characterized by rapid progression of muscle weakness and dysphagia in middle-aged adults?

The condition characterized by rapid progression of muscle weakness and dysphagia in middle-aged adults is polymyositis. This inflammatory myopathy primarily affects skeletal muscle, leading to symmetrical proximal muscle weakness. Patients often experience significant muscle fatigue and difficulty swallowing, known as dysphagia, due to the involvement of the muscles responsible for swallowing.

Polymyositis is particularly noted for its acute or subacute onset in adults, typically presenting in middle age. This distinguishes it from conditions like muscular dystrophy, which usually manifests with a more gradual onset and is typically recognized earlier in life. Inclusion body myositis, while it can also cause weakness and dysphagia, tends to be more slowly progressive and often affects older adults. Myasthenia gravis is characterized by fluctuating muscle weakness and ocular symptoms, but it does not typically present with rapid generalized muscle weakness or dysphagia in the same manner as polymyositis.

Therefore, the specific combination of rapid progression of weakness and dysphagia in this age group strongly points to polymyositis as the underlying condition.