Malacanang downplayed on Monday President Rodrigo Duterte's latest health problem involving his skeletal muscles.

In a speech before the Filipino community in Russia on October 5, Duterte disclosed that he has myasthenia gravis.

"Actually my - that's myasthenia gravis. It's a nerve malfunction. I got it from my --- exactly from my grandfather, it's like in the genetics," he said.

According to the National Institute of Neurological Disorders, myasthenia gravis is a chronic auto-immune neuro-muscular disease that causes weakness in the skeletal muscles, which are responsible for breathing and moving parts of the body, including the arms and legs.

The hallmark of myasthenia gravis is muscle weakness that worsens after periods of activity and improves after periods of rest, the National Institute said.

It added that certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often (but not always) involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.

Panelo said that Duterte's disclosure of his health condition showed how transparent he is.

But he assured the public that there was nothing to be worried about Duterte's health.

"I don't think it's that serious for us to worry about," he said.

The 74-year-old Duterte previously admitted he was suffering from Buerger's disease because he smoked too much when he was still young.

His doctors also regularly conduct blood tests on the President.

He previously underwent repeated colonoscopy.

Duterte also admitted before he was using fentanyl due to his spinal injury when he had a motorcycle accident. Celerina Monte/DMS