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.
Cysts develop in the inner part (medulla) of the kidney. The kidneys shrink as the outer section thins. MCKD often causes kidney failure in people between the ages of 20 and 50 years. In a few cases, there is no family history, which may indicate a genetic mutation.