Chelsea Jackson, 20, was struck down with a sore throat last December.
Doctors initially told her she had glandular fever but when her condition worsened they diagnosed tonsillitis and gave her antibiotics.
When the student, from Wolverhampton, later began struggling to breathe and her eyes turned yellow she was rushed to hospital and placed on a life-support machine.
Baffled medics were unable to find out what was wrong with her until they tested for Hemophagocytic lymphohistiocytosis (HLH), a rare, life-threatening immune condition.
It causes organ failure by destroying healthy cells.
Chelsea’s liver struggled to cope with the infection and three days later, on January 17, she died.
Her devastated mother, Nicki Jackson, 41, father Scott, 44, and sister Lauren, 23, were at her side.
Mrs Jackson, a sales assistant, said: “Chelsea was never really ill so when she started to complain of a sore throat we assumed she’d caught a cold. No one expected her to die, it’s awful.”
The family wants to raise awareness about HLH and yesterday launched a charity in her name.
Lauren said: “We want to keep her memory alive. The more people who know HLH exists the better.”