I seem to have bumped into it a lot in the game I'm AARing (read! c'mon, please!)
My first ruler was Sergio Spartenos. He is succeeded by his son, also named Sergio. He dies of pneumonia. He is succeeded by Isaakios, one of his three sons. Isaakios has pneumonia and simply awful stats. I kill him off with F12. His brother Alexandros succeeds him, luckily lacking pneumonia. Alexandros dies, his son Andronikos reaching the throne. Andronikos gets wounded, which leads to illness, which leads to (you guessed it) pneumonia. He snuffs it. His eldest son is Dragos. One of Dragos' sons, also Andronikos, gets pneumonia and dies. Dragos gets wounded in battle, leading to illness and pneumonia. Not dead yet, but his stewardship is down to 1. The score so far is:
Pneumonia: 4
Leprosy: 0
Black Death: 0
Stomach Worms: 0
My first ruler was Sergio Spartenos. He is succeeded by his son, also named Sergio. He dies of pneumonia. He is succeeded by Isaakios, one of his three sons. Isaakios has pneumonia and simply awful stats. I kill him off with F12. His brother Alexandros succeeds him, luckily lacking pneumonia. Alexandros dies, his son Andronikos reaching the throne. Andronikos gets wounded, which leads to illness, which leads to (you guessed it) pneumonia. He snuffs it. His eldest son is Dragos. One of Dragos' sons, also Andronikos, gets pneumonia and dies. Dragos gets wounded in battle, leading to illness and pneumonia. Not dead yet, but his stewardship is down to 1. The score so far is:
Pneumonia: 4
Leprosy: 0
Black Death: 0
Stomach Worms: 0