Non‐paraneoplastic Lambert–Eaton myasthenic syndrome presenting dropped head and respiratory failure with normoreflexia

A 57‐year‐old woman developed insidious dropped head, respiratory failure and autonomic dysfunction with inconspicuous limb weakness, but without diminished deep tendon reflexes. Progressive myopathy affecting truncal muscles was initially suspected, but non‐paraneoplastic Lambert–Eaton myasthenic syndrome was finally diagnosed based on the results of electrophysiological studies and positivity for anti‐P/Q‐type voltage‐gated calcium channel antibody without any evidence of malignancy. In general, most patients with Lambert–Eaton myasthenic syndrome have more than one of the core manifestations of Lambert–Eaton myasthenic syndrome including proximal‐dominant limb weakness, diminished or absent deep tendon reflexes and autonomic dysfunction. However, this patient presented atypical manifestations, and lacked two core manifestations except for autonomic dysfunction. It is important to take Lambert–Eaton myasthenic syndrome into consideration in the differential diagnosis of patients showing atypical presentation, such as dropped head or respiratory failure, when they have only one core manifestation of Lambert–Eaton myasthenic syndrome.