Dermatofibroma are common benign skin tumours that cause lumps in the skin and frequently cause concern upon discovery. The causes of dermatofibroma may include a reaction to trauma such as insect bites but the precise cause is often unclear.
Causes. It's not clear what causes simple kidney cysts. One theory suggests that kidney cysts develop when the surface layer of the kidney weakens and forms a pouch (diverticulum). The pouch then fills with fluid, detaches and develops into a cyst. 1  Symptoms. 2  Risk factors.
Cystic kidney disease is a group of diseases that cause abnormal pockets of clear, watery fluid (cysts) to form in the kidneys. Cystic kidney diseases include polycystic kidney disease, medullary cystic disease and medullary sponge kidney. The cysts interfere with normal kidney function and may cause kidney failure.