It is pertinent to mention here that the former premier along with his family, is facing three corruption cases filed by the National Accountability Bureau (NAB) following his disqualification in July last year.
Begum Kulsoom was shifted to the Intensive Care Unit (ICU) of the Harley Street Clinic in London after she suffered a cardiac arrest late on Thursday, Geo TV reported.
She has been kept on life support since then but is now said to be stable.
Pakistan Muslim League-Nawaz (PML-N) President Shehbaz Sharif on Saturday arrived in London to see his ailing sister-in-law.
Begum Kulsoom Nawaz underwent multiple surgeries from August 2017, after she was diagnosed with throat cancer (lymphoma). Her condition began to deteriorate in April this year, after which she was moved to London for treatment.