After an update on international pop star Celine Dion's stiff person syndrome diagnosis, many fans have been left wondering what it is.

The Canadian singer recently cancelled her world tour, seeing many of her UK dates scrapped.

Her sister said of her decision to cancel her shows: “I honestly think that she mostly needs to rest. She always goes above and beyond; she always tries to be the best and top of her game.”

Celine Dion's sister added: “At one point, your heart and your body are trying to tell you something. It’s important to listen to it.”

What is stiff person syndrome after Celine Dion's diagnosis?

According to the National Institute of Neurological Disorders, Stiff person syndrome (SPS) is a rare neurological disorder that causes progressive muscle stiffness and repeated and painful episodes of muscle spasms.

The rigidity's severity fluctuates, growing better, then worse, randomly.

Spasms can also be triggered by a number of stimuli such as sudden noise, light physical contact or when exposed to the cold.

If left untreated, the condition can worsen and affect the person's ability to carry out daily tasks such as walking.

What is the life expectancy of someone with stiff person syndrome?

MedicineNet says that a person can live between 6-28 years from the initial symptoms before dying.

Can you recover from stiff person syndrome?

There is no cure for SPS but some treatments exist to help manage the symptoms or slow the progression of the condition.

A number of medicines and therapies exist with patients able to seek out immunotherapy or disease-modifying treatments.

What triggers stiff person syndrome?

Very little is known about SPS with it thought to be caused by an autoimmune reaction.

The immune system may attack a protein called glutamic acid decarboxylase which helps to produce a substance called gamma-aminobutyric acid.