Haemophilia is a rare blood disorder - affecting about one in every 10,000 births.
It is mostly genetic and it affects your body's ability to clot your blood.
Those with the conditon must stay away from risky activities and sports, which might see them take a fall and get injured.
Alex Dowsett is a British former professional road racing cyclist who lives with haemophilia - but it hasn't stopped him.
He competed in seven Grand Tours for both Team Sky and Movistar, and in 2015 broke the fabled cycling hour record by 446 metres.
He recently released a book called Bloody Minded: My Life in Cycling, and he has a very special connection with New Zealand.