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    How to recognize sinus tracts, keratinous cysts


    Injection techniques

    Dr. Siegfried: When you recognize those patients, what do you do then?

    Dr. Leyden: I think intralesional steroids are very useful for keratinous cysts if they are inflamed. Sometimes when you inject an inflamed keratinous cyst, the whole thing seems to melt, or enough of it melts that nothing more needs to be done. But if it’s constantly recurring, it has to be removed the same way the sinus tract lesion is. If it is persistent and doesn’t respond to intralesional steroid, I think then it should be removed.

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    Dr. Siegfried: So when you inject cysts, do you do it into the cyst cavity or in the periphery?

    Dr. Leyden: I mostly put it into the cavity, because I think a lot of it diffuses. The question is: Could you do better by injecting the periphery? That’s an interesting question. I think one of the things that is most interesting about injecting steroids in the skin is if you get anywhere near the subcutaneous layer, significant atrophy can develop.  

    Dr. Siegfried: But injecting into the cyst cavity has the potential to cause micro-rupture of the cyst resulting in terrible inflammation. If you inject around the cyst, then you get atrophy. How do you manage that?

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    Dr. Leyden: I us a 30-gauge needle — and my general rule is, depending on the size, no more than 1 mg to 3 mg of steroid. I do not believe in injecting until it blanches. Once you see blanching, that’s a sign of increased pressure, and that’s usually when it hurts and may rupture. I think it is the amount you want to put in that is important, not the volume. You figure out how to put in 1 mg, but you could put in 5 cc if you dilute it enough. I think if you have a 10 mg/mL syringe, then a 0.1 mL will have 1 mg. And if you inject 0.2 mg into an inflamed keratinous cyst, you’re not going to get rupture of the cyst and it’s not going to hurt. This way, you put in the amount you want, but the volume is not big enough to cause blanching and distention and/or rupture of the cyst.

    Dr. Siegfried: So that’s a good pearl. It is another area of constant and common-use treatment that all dermatologists are taught to do with such variation in technique and dose, and I think the outcomes can vary.

    Dr. Leyden: Right from the time I started doing it, I noticed when patients started saying, “Boy, that hurts,” which always seemed to be just as it blanched. That’s when I started backtracking the volume and paying attention to amount and how often do I get an atrophy. That’s how I came to the 1 mg to 3 mg dose per cyst.

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    Dr. Siegfried: You can try that with sinus tracts as well?

    Dr. Leyden: For sure. Once you learn, if you take your time, you can actually get into the tract and you can get much more easily into the cyst. You can follow the epithelium, the actual sinus and inject it with a lot less discomfort.

    Dr. Siegfried: That’s a great pearl. Thank you.

    Elaine Siegfried, M.D.
    Elaine Siegfried, M.D., is professor of pediatrics and dermatology, Saint Louis University Health Sciences Center, St. Louis, Mo. She ...


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