The skin is the body’s largest organ, so it makes sense that many systemic diseases may express themselves on the skin. Jeffrey P. Callen, MD, FACP, FAAD, MACR, a Professor of Medicine and Chief of the Division of Dermatology at the University of Louisville School of Medicine in Louisville, KY, literally wrote the book on this topic. First published in 1978, his book, Dermatological Signs of Systemic Disease, is now in its 5th printing, reflecting just how much has changed in terms of our understanding of the cutaneous signs of systemic disease and their diagnostic and treatment implications.
How did you become interested in cutaneous manifestations of internal diseases?
Dr. Callen: My father was a cardiologist. When I went to medical school I was quickly convinced that internal medicine was a good fit for me and in my second year of medical residency I decided to apply for a cardiology fellowship. I was accepted in a program run by a superb clinician, but my plans were derailed when during my first month of my third year of internal medicine residency I rotated in dermatology. One of my classmates from medical school was due to become the Chief Resident the following year and told me of an opening. It was not an easy decision to give up the plum cardiology slot, but I had been smitten by the complexity of dermatology and the visual ability to make diagnoses. Bottom line: I gave up cardiology for dermatology.
What are some of the subtle dermatological signs that may occur with internal disease?
Dr. Callen: Acanthosis nigricans (AN), which is a velvety hyperpigmentation on the neck and axillae, is sometimes very subtle and patients with this condition are almost always overweight or obese. They rarely come to the office with a chief complaint relating to acanthosis nigricans and rather might present for treatment of acne or hirsutism. Noticing the changes on the neck or elsewhere should trigger the physician to think about the possibility of insulin resistance. Intervention with diet, exercise, and sometimes medication can not only help resolve the AN, but might have benefit for the presenting skin disorder and in the long-run might result in improved health through weight reduction.
Do you have an example of the management implications when an internal disease expresses itself on the skin?
Dr. Callen: Dermatomyositis is a disease of the skin and muscles, but patients with this condition might have or develop a malignancy. So at the time of diagnosis, a careful history, physical examination, and testing should be performed. The chance of subsequent malignancy reduces toward normal within three to five years, but some form of surveillance is needed. The exact testing and its timing have not been adequately worked out so further research is needed. In addition, some patients with primarily skin- limited dermatomyositis might have pulmonary disease, so careful assessment and monitoring for this complication is also needed.
Is there a knowledge gap regarding dermatological signs of internal disease among non-dermatologists?
Dr. Callen: Non-dermatologists received between several days and perhaps two months (of dermatology training) during medical school and post-graduate training so there are gaps in their knowledge on many subjects in dermatology as well as many specialties. The intricacies of which skin disease might suggest internal disease, a knowledge of how to assess patients for internal disease, and how and when to evaluate and monitor such patients is beyond their native abilities. Fortunately there are multiple sources in which information can be accessed including one that I edit at UpToDate.com.
When should non-dermatologists refer out skin manifestations, and on the flip side, when should dermatologists refer patients to internists or other specialists?
Dr. Callen: We need to function as a team. When diagnosis is not clear, non-dermatologists should refer to a dermatologist. Dermatologists need to be knowledgeable about skin manifestations of internal disease and know how and when to evaluate patients and to not rely on internists, family physicians, or pediatricians for advice. That said, dermatologists should use the assistance of a non-dermatologist when there is something in terms of evaluation or treatment that they are not familiar with and when the primary care physician possesses knowledge to manage that problem or medication.
