Dusting off the keyboard

Mar 31 2011 Published by under Medicine

I itch---a lot.  Mrs. Pal swears it's scabies, impetigo, or some other horrible and embarrassing contagion.  I suggested body lice, to which she replied, "There's such a thing as body lice? Ech! Sleep in the guest room!"

It's not any of those things (thank Asclepius), but I'm gaining a new level of empathy for patients with rashes.  Luckily I was able to carve a chunk of time out of my schedule tomorrow to head over to the dermatologist, a specialty for which I suddenly have a renewed respect.  (I'm betting on guttae psoriasis, which means it cannot be guttae psoriasis).

Rashes are a fascinating area of medicine.  The skin is incredibly complex, forming a physical barrier between our important bits and the environment, but also a living shield patrolled by immune cells who mark and attack invaders and create a cellular memory to defend against future attacks.   Diseases that injure this barrier open us up to horrible infections.  Burn patients often die of fluid loss and overwhelming infections, but any significant injury to the skin can have similarly bad results.

Being so immunologically active, the skin is susceptible to "friendly fire", where our own immune system either attacks the skin or causes uncomfortable reactions (among these are common diseases such as psoriasis, hives, and eczema).  Skin contains many different kinds of cells, and something can go wrong with all of them.  Skin cancers are very common, especially the "benign" sorts like basal and squamous cell cancers.  Cancers of skin pigment cells, called malignant melanomas, are often deadly.

The complexity of skin and all the things that can go wrong with it are endlessly fascinating, and endlessly frustrating for internists.  To non-dermatologists, just about all rashes can look "red and bumpy", a completely un-helpful assessment.  But most people with rashes come to see me before they get to a dermatologist, so I constantly work on refining my ability to describe and diagnose skin conditions.

This time of year, I start to see my first cases of rhus phytodermatitis (that's poison ivy---I think dermatologists keep the competition down by giving every thing Greek and Latin names).  People are starting to do a little spring cleaning and the classic "leaves of three, let them be" aren't out yet, just vines and stems covered in nasty urushiol.   It should be at least another month or two before I start seeing mosquito bites (yes, people come to the doctor for them) and sun burns.

I'm pretty good at spotting psoriasis, seborrheic dermatitis, eczema, and other common rashes, but when it comes to skin, it's not that hard to stump me. I might not always know what a rash is caused by, but I usually know when I need to refer to an expert, and right now I'm counting on benadryl to keep me going until tomorrow.


11 responses so far

  • becca says:

    Immunologically, skin makes no *sense* to me. I mean, it's incredibly important and interesting, but it seems like all the cell signaling pathways are backasswards. The main phenotype for the knockout mouse for my favorite gene is atopic dermatitis. Now, this is a gene that was originally characterized in macrophages, and seems to help boost cytokine production there. So how does getting rid of it produce auto-immune like problems, with elevated levels of the same cytokines?

  • longsmith says:

    This is so timely! My husband has an idiopathic case of hives which just will not go away. It's driving him (and me) nuts.

  • DaveH says:

    @ becca:

    Because our immune system, just like every other system in nature, is a kludgy one. The answer to your question is the same as the old answer to "why is the eye wired 'backwards'"?

  • Dianne says:

    Skin cancers are very common, especially the "benign" sorts like basal and squamous cell cancers.

    Just to point out, basal and squamous cell cancers may be "benign" in that basal cell cancers never and squamous cell skin cancers rarely metastasize to distant parts of the body, but that doesn't mean that they're harmless. I've seen 3 cases of basal/squamous cell cancers that led to severe nastiness.

    One was a woman with a basal cell cancer on her ear. She knew it was there, but she was an illegal immigrant and afraid to seek medical care-until the cancer had wrapped itself around her carotid artery and given her a stroke. By which time it was no longer operable.

    The second was a woman whose squamous cell cancer just kept coming back. First it was removed (from her forehead). Then it was removed and radiated. Then it grew back and invaded her brain and eye. The neurosurgeons described pictures of her surgery as "graphic" and there are few weak stomached neurosurgeons in the world.

    The third had a squamous cell cancer that did metastasize to his sinuses. It's a nasty one, but luckily is chemosensitive. For now. We'll see where things go from here.

  • daedalus2u says:

    Becca, one of the important things that cytokines do is produce enough inflammation to balance the right NO level. Not enough cytokines, not enough NO, the mast cells become potentiated, mast cell hypersensitivity, then mast cell degranulation.

    What is needed is more NO to turn off NFkB and make mast cells less sensitive.

  • Donna B. says:


    That's the only bug that's ever sent me to the doctor. And thank goodness he could help. Now, I don't go out in the yard without "protection". That means long pants, with long socks over them and high topped boots. Also I keep my shirt tucked in and it's a long sleeved one.

    Chiggers and snakes are almost enough to make me leave the south... except there are mosquitoes and bigger snakes elsewhere.


  • Our elderly lab developed seasonal allergies for the first time ever last week. Not that signifies anything in particular, but is there credible evidence for a looming severe allergy season this year?

    Completely OT, but this is interesting. A newborn had what parents called "mild" jaundice. Pediatricians recommended NICU, parents refused and tried to discharge AMA, and a nurse called police. Why recommend NICU for anything labelled "mild?"

  • JJM says:

    You have had us in suspense long-enough.

  • Steve Schonfeld says:

    Rhus is the old name of the genus which contains poison ivy (Rhus toxicodendron was the name that old farts like me were taught).