A heartbroken mother has urged parents not to blame childrens' lingering coughs on a change of season - after the symptom turned out to be a sign of deadly heart disease that killed her three-year-old.

EXCLUSIVE. WARNING: DISTRESSING CONTENT It began as just a cough, but Penny Dunn's heartbroken parents are telling their tragic story in a bid to warn others

A heartbroken mother has urged parents not to blame childrens' lingering coughs on a change of season - after the symptom turned out to be a sign of deadly heart disease that…