6. Proteus syndrome
Proteus syndrome is characterized by the overgrowth of skeletal and skin tissue and organs. The growth is disproportional, affecting the left and the right side of the body differently. In certain cases, people with this genetic mutation have intellectual disability, seizures or vision loss. The syndrome affects 1 in a million people worldwide, which is why it is ranked 6th on our list of 10 uncommon genetic mutations in humans.