A genetically inherited disease in children that results in chronic fluid development in the lungs, making breathing difficult. This disease also prevents normal absorption of fats and other nutrients from food. Cystic fibrosis occurs as a result of inheriting a recessive allele for if from both parents. This is ultimately a fatal disease, but with modern medical care, about 2/3 of the people with it survive into early adulthood. About 30,000 people have cystic fibrosis in the U. S. Today.