|Manet died of a disease called locomotor ataxia which attacks the central nervous system and causes paralysis. It was brought on by untreated syphilis, which Manet probably contracted early in his life. It also didn't help that he had to have his left foot amputated eleven days before he died because gangrene had set in.
Manet began his career late in life, but he developed his talent quickly. His last works revealed no deterioration in quality and we were cheated out of Manet's final phase. What would he have gone on to produce in his later years wil, sadly, remain unknown.