At age 16, Peter visits his family doctor for the first time because of macroscopic haematuria. He’s also worried about the fact his abdomen keeps growing in size. His blood pressure is 150/110 mm Hg and the abdominal ultrasound shows multiple cysts over both kidneys, varying in size. His plasma creatinine is 110 micromol/l. He’s successfully treated with antihypertensive drugs. The boy’s mother, who is also hypertensive, turns out to have polycystic kidneys as well. It is concluded that both patients have the autosomal dominant form of polycystic kidney disease. Another ultrasound reveals that Peter’s younger brother – aged 10 – does not have polycystic kidneys. Questions. 1. Does this mean the brother has not been affected with the autosomal dominant form of polycystic kidney disease? 2. After browsing the internet, Peter wonders if further investigations of his brain have to take place in order to detect small vessel anomalies. What would you tell him? 3. What is the chance of Peter’s future children being affected?