Diagnostic surprises are unusual, often not recognized

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Anneli Bowen, MD: “After I saw them several times in one year, I started to wonder if maybe they weren’t more common than they seemed to be in the literature.”

Medical practice is filled with diagnoses that are relatively common and almost never recognized. Dermatology is no different.

“One of the things I enjoy about being both a dermatologist and a dermatopathologist is seeing the rare and unusual, and getting to be involved in the diagnosis of what we like to call ‘zebras,’” said Anneli Bowen, MD, associate professor of dermatology at University of Utah Health Sciences, Salt Lake City. “There were a few diagnoses that started out as zebras, but after I saw them several times in one year, I started to wonder if maybe they weren’t more common than they seemed to be in the literature.”

What Dr. Bowen found was a subset of dermatologic conditions that occur on a fairly routine basis but are not widely recognized. The result was the first-ever Summer Academy Meeting session, “Dermatoses You’ve Probably Seen But Never Heard Of” (B010). The session was co-presented with University of Utah associate professor and dermatopathologist Scott Robert Florell, MD.

Take, for example, a patient who presents with discrete papules that are very itchy and confined to the shins. It’s the kind of distinctive rash that walks through the door of many dermatologic exam rooms several times a year. But it’s a rare dermatologist who can recognize pretibial pruritic papular dermatitis (PPPD) without more than a little confusion. PPPD is nothing more than a very distinctive cutaneous manifestation in response to delicate and persistent rubbing of the skin.

“I have found that it can be easily confused with lymphomatoid papulosis, for instance, and several other diagnoses even in my own practice,” Dr. Bowen said. “PPPD can be difficult to treat, but it’s important to distinguish it from a lymphoma or some other condition that has a very different method of treatment and a dramatically different prognosis.”

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Dr. Bowen: “The last thing you want is to find yourself going down a route of workup and treatment that is unnecessary.”

Most dermatologic practices have at least a few patients in their 70s, 80, even their 90s. Older individuals who are thin may present with irritated skin on the buttocks that looks like corrugated cardboard. But these lesions often produce no pain or discomfort. Dr. Bowen said she most often sees hyperkeratotic lichenified skin lesion of the gluteal region, also known as sitter’s sign, as an incidental finding during a skin exam. Patients rarely see their own buttocks and don’t even realize they have a problem, though rare patients complain of tenderness or pruritus.

“This is thought to be a skin change that develops in response to prolonged mechanical irritation from sitting,” she said. “Patients who have it tend to be thin and spend a lot of their day sitting. It is not dangerous in and of itself, but it can be confused with things like mycosis fungoides or macular amyloidosis that would require very different treatment from the keratolytics or topical steroids that we would usually recommend.”

The good news is that these lesions rarely ulcerate. Unlike pressure sores, there is no underlying problem with circulation, simply prolonged mechanical irritation. The clinician should probably recommend that the patient reduce the irritation by spending less time sitting, but this may not be a practical alternative for some older patients. Donut cushions have been effective in improving symptoms.

“The real concern is that patients know what is happening and for the clinician to recognize this condition,” Dr. Bowen said. “The last thing you want is to find yourself going down a route of workup and treatment that is unnecessary.”

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