MANILA — President Rodrigo Duterte of the Philippines has revealed that he has a neuromuscular disease that has led to a slew of medical problems, including making his eye droop.

Mr. Duterte, who was in Russia for a state visit, told the Filipino community there on Saturday night that he has myasthenia gravis, a chronic autoimmune disease that leads to skeletal muscle weakness. He said the disease ran in his family.

The revelation came amid continued public speculation about his health. There have been periods when the famously bombastic president has been out of the public eye for days, prompting headlines guessing about his whereabouts, and even rumors of his death.

But his communications officers have said that Mr. Duterte, 74, like any other older person, needs his own personal time.