"Begum Kulsoom Nawaz has been under treatment in a hospital in London as her condition is serious," the family spokesperson said, adding that because of her serious condition Sharif and his daughter have to be with her.
Maryam also tweeted about her mother.
"My mother is hospitalised again. Remember her in your special prayers. I know prayers can do wonders. Allah answers prayers," Maryam tweeted.
Kulsoom, last year, had undergone a surgery for lymphoma (throat cancer). Her condition recently deteriorated and she was hospitalised.
Last week, Pakistan Prime Minister Shahid Khakan Abbasi had shown reluctance to place the names of Nawaz Sharif and his family on the Exit Control List (ECL).
The NAB had asked to include on the ECL the names of Sharif's children - Maryam, Hassan and Hussain - his son-in-law retired Captain Safdar Awan.
All of them are being tried in accountability courts regarding the Panama Leaks cases. His both sons are already in London. They have been declared proclaimed offenders by the accountability court in the corruption cases against them.
Opposition parties especially the Pakistan Tehreek-i-Insaf has criticised the government for not placing the Sharif family on ECL.
"Nawaz Sharif and Maryam left the country at the time when a decision against them by the accountability court is about to come," Pakistan Tehreek-i-Insaf senior leader Babar Awan said and claimed that Sharif would not return the country.
"Nawaz Sharif has left the country on the pretext of his wife's ailment," he said.