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Rash on right knee

Hi Doc, firstly, your work is much appreciated.

Last summer i developed a rash on my right knee, located slightly to outside of leg and parallel to kneecap.

-The rash covered an an area of about a square inch or inch and half

-The area affected was not a symetrical circle, but rather an uneven asymetrical shape with a couple of smaller "blotches" around the perimeter of the main larger "blotch" or blending into the larger "blotch".

-The initial onset was sudden (over a day) and the affected skin looked red (almost like an initial carpet burn or scrape on concrete), it also burned slightly but did not really itch.

-Over the next couple of days the affected skin turned darker (brown) and it seemed as if a scab developed over the area and the skin peeled off.

-The skin below remained pink and shiny (similar to psoriasis pics ive seen on the net), but it seemed like there were a million little dots that actually comprised the shape of the rash. For the next 7-10 days or so it only itched a little.

-At roughly 21 days the lesion started to go away, but after a shower the affected skin would still redden and puff up a bit and it would look like there were very many little tiny white dots that make up the area of the affected skin.

-at 40-45 days the rash was pretty much completely gone.

-The rash never expanded or imploded beyond the initally "irritated" area

Now, a year later, the area of the original rash is ever so slighlty paler relative to the surrouding skin. (You really have to stretch the skin and look hard to see this, but the outline is undoubtedly still there) And i still sometimes feel the area slighly itch, but that could just be my mind playing tricks on me.

To close: Im sure there was no trauma to the area (and the shape was so abnormal and ambigous Im not sure i could scrape myself this way if i tried) Also, I am slighly allergic to cats, and I slept in a cat hair infested bed the night or two before the rash developed.

Sorry for the long text, finally my questions:

1.My father is a doc and without seeing the rash he advised if it goes away on its own not to worry about it. However do you think there are any systemic issues or diseases I should be worried about from the described (rash was on right knee only)?

2.Also, like many people Im paranoid about STD's, particularly HIV. I am straight, dont use drugs, but had an act of unprotected sex with a woman about 6 yrs ago that worries me. While I think the chances she had HIV were very low, I worry about things like this spontaneous rash.

If Im otherwise healthy (i get a cold sore on my lip every yr or so) a rash like this wouldn't be a sign that HIV had weakened my immune system if i fought it off without any treatment 6 yrs later?

Sorry if the questions sound ignorant, but paranoia has taken its toll.

Thanks very much doctor.


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242489 tn?1210500813
I agree with your father.  This rash, whatever it was, does not sound in any way related to systemic diseases or STD's.  Rashes localized to one area often reflect local irritation of some sort.  I suggest you forget about it.


Dr. Rockoff
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Avatar universal
My son is experincing the same thing but he got it after swimming in a big pool
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