Recognizing the unusual: Rare diognoses take suspicion and thorough evaluation

May 1, 2008

Whether it is a melanoma on the breast, a case of leprosy or chromoblastomycosis, diagnosing the not-so-obvious and not-so-common skin conditions takes an index of suspicion and thorough evaluation.

Key Points

"Dermatologists tend to be well attuned to even the rare skin conditions," says Robert Auerbach, M.D., clinical professor of dermatology, New York University School of Medicine.

"I worry more about nondermatologists who try to make diagnoses of skin conditions. However, for everyone, the trick is to sit down and think about the possibilities. Do not make a knee-jerk reaction," he says.

Dr. Auerbach offers multiple examples of classic misdiagnoses. He has seen patients diagnosed with male-pattern or female-pattern hair loss when, in fact, they had cicatricial alopecia.

"Some of them have plenty of hair left, and under the thick hair, you have the scarring. The bottom line is you have to be very careful examining scalps because you have to get through the hair. Unusual skin cancers can occur under the hair, and are rare, but they will be missed if you do not push back the hair and look," Dr. Auerbach says.

The dermatologist recently saw a patient with a melanoma on her breast. A breast surgeon told her not to worry. Lung cancer metastatic to the skin also occurs, he says.

"What you see, usually, is a hard lump or nodule that is dermal and subcutaneous, or maybe even just dermal. You have to be careful not to call it a dermatofibroma, especially when it occurs in areas where we generally do not see dermatofibromas, such as the trunk," Dr. Auerbach tells Dermatology Times

The unusual

Though rare, Dr. Auerbach says he pieced together a diagnosis of chromoblastomycosis, a fungal infection, in a patient who had nonhealing ulcers (despite all types of treatment). The American patient, he says, had worked unloading crates on the docks.

"When we took a biopsy, I suspected something esoteric, and alerted the laboratory to do stains for deep fungal organisms. I figured it could be something from the wood on the docks," he says.

It is not out of the question to run across cases of leprosy, Dr. Auerbach says. And he says that dermatologists in New York, Miami, the West Coast and other areas of the country should be alert.

"We have a lot of immigrants from countries where leprosy is endemic," he says.

Leishmaniasis occurs in travelers who have visited other countries. Dr. Auerbach diagnosed it in a patient who had hundreds of insect bites after a trip to South America. All the bites, except two, healed. After learning the patient had visited an area where leishmaniasis was endemic, Dr. Auerbach took a biopsy to confirm presence of the mosquito-spread parasite.