Hi Limin ward welcome to the forum. I am unsure why you are asking, but suspect that you may be worried that this something that you/or family may have or suspect something is wrong. If tna is the case and you are at all worried then please don't wait just make an appointment with your GP and speak to them about any concerns that you may have.
Please whatever you do STAY OFF GOOGLE the searches are not specific enough to each individual case and can often make situations worse by worrying people more than is necessary.
If you wanted to post more info then people can try to help as best they can.
