MUSK and ptosis: Subtypes include patients with antibodies targeting the acetylcholinereceptor, and against the muscle specific kinase receptor, with variable phenotype,including treatment response, depending on the category of autoimmune antibody.Patients, usually older middle-aged people or young women, often primarily presentwith eyelid weakness (ptosis) or difficulty swallowing (dysphagia) or other signs ofweakness.