Usage patterns
疾患にかかるto contract/develop a disease
He developed a heart condition when he was young.
疾患を患うto suffer from a disease
My grandmother has suffered from a kidney disorder for many years.
疾患が見つかるa disease/disorder is discovered (in a checkup or test)
The test results revealed a disorder in his lungs.
疾患を治療するto treat a disease/disorder
This hospital treats a wide variety of medical conditions.