my older sister magdalein succumbed to sickle cell. paul: the sister who i lost, i never met her. she died before i was born. based on the way sickle cell and just the way we live. you know how it affected my parents, my sisters. i could see that that created like a kind of environment. ♪ lea: sickle cell has made me and my family stronger. but as i prepare for the marathon, the warnings from my doctor keep playing on my mind. the doctors disagree with me about my doing the marathon. essentially, i will be reducing the oxygen supply in my body, the functionally of my organs, and risking things like strokes or now retinopathy or like something just obstruct somewhere and it'll just collapse, and yeah. as the day approaches, i'm excited and determined. announcer: ladies and gentlemen, we would like to welcome you to the 2018 standard chartered nairobi international marathon. lea: i'm feeling good at the starting line. the adrenaline kicks in and i'm all set. woo! (gunshot). (cheering and applause). after two kilometers, my body starts to give out. the n is so hot, my breathing bec