Replacing bone marrow can promote the growth of healthy cells and fight cancer.
For many children a transplant is their only hope – but it is fading for Venezuelans.
The government says it can not pay for treatments because of US sanctions.
The opposition blames inefficiency and a lack of resources.
We spoke to a group of around 30 children needing bone marrow transplants. Time has just run out for one of them.
Al Jazeera’s Teresa Bo reports.