By Gary M. White, MD
The acne cyst is not a true cyst (with an epithelial wall, e.g., epidermal inclusion cyst), but instead a focus of inflammation. It is usually caused by the rupture of a follicle as a consequence of the pressure and inflammation of the acne.
The acute appearance of an inflammatory papulonodule on the face or trunk in a patient with acne is characteristic. An acne cyst may last for days, weeks, or rarely months, but at some point resolves. An epidermal inclusion cyst, in contrast, stays fixed in size or grows, has less inflammation, and is spherical in shape. One key point here is to palpate the lesion.
If left alone, the lesion will spontaneously resolve in days, weeks, or occasionally months. IL injection with Kenalog 3 mg/cc x 0.1 cc will shrink the lesion within days. The main risk is overshooting the goal and making a depressed, atrophic area. If this does happen however, resolution usually occurs within a month as long as the concentration of triamcinolone is kept low. Some give a high-potency steroid (e.g., fluocinonide gel) BID x 2 days at the onset of any new, larger cyst.
A different approach is to inject into each cyst a total dose of 1-3 mg of Kenalog depending upon the size of the cyst. For example, using Kenalog 10 mg/cc solution means you inject 0.1-0.3 cc. Inject using a 30 gauge needle into the cyst itself and not the surrounding tissue to minimize the risk of atrophy. There is no need to "inject until the cyst blanches" with this technique. In fact, this is discouraged as blanching often means higher pressure and pain for the patient.
Any background acne should be addressed and often oral antibiotics or isotretinoin are required. See acne treatment. Scarring may result and when present, is all the more reason to be aggressive with acne therapy.
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