MadSci Network: Medicine

Re: White dots on fingernails

Date: Mon Feb 9 20:42:05 1998
Posted By: Tom Wilson, M.D./PhD, Pathology, Div. of Molecular Oncology, Washington University School of Medicine
Area of science: Medicine
ID: 885835097.Me

The white dots that people sometimes get in their fingernails have a 
medical name.  It is "leuconychia" (pronounced loo-ko-nee-kee-a, also 
spelled leukonychia).

The white dots come about as a result of damage to the fingernail as it 
grows.  Basically, if you hit your finger on something it can cause a 
deformity (often called an "air bubble") in the fingernail.  What it really 
represents is an area where the material that makes up the fingernail 
(called keratin) is not put together quite right (we say it is incompletely 
keratinized).  This deformity stays in the nail until it grows out and gets 
cut off.

To really understand this, you need to understand how a fingernail grows.  
Most of your fingernail is "dead", like your hair.  But there is a part 
toward the back, closer to your knuckle, and mostly under the skin, that is 
alive and growing (push on this part of your fingernail to see how much it 
hurts).  This part of your fingernail is always growing and "pushing" on 
the rest of your fingernail, causing it to "slide" over your finger.  In 
other words, the end of your fingernail was, at one time, way at the back 
end under your skin.

When you hit your finger on something, you can damage the part of your 
fingernail that is alive and growing.  This doesnít cause any permanent 
problems, but causes this white spot in your nail.  The more you bump or 
hit your fingernail, the more white spots you will get.  But whether you 
have one or many, they stay in your nail until it grows out.

Click here to 
see a very dramatic example of this.  This is a picture of a 
person who took a drug several times that damaged the growing part of their 
fingernail.  These are the white arcs in the nail.  The darker areas in 
between are the parts of the nail that were made when the person was not 
taking the drug, and look more normal.  These bands on this personís 
fingernails will remain there until they grow out and get pushed off the 
end of the finger and cut off.  This is just an extreme example of the 
white spots you are talking about.

Tom Wilson MD PhD

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