What would you expect to find as you travel over any particular person’s cutaneous terrain? If I encounter the short timber of a cutaneous horn—a hard, horn-shaped tumor—I know to be cautious and to collect a sample that includes the base of the tumor when doing a biopsy, where the squamous cell layer may harbor a cancer. If a patient comes to me with a fire-like eruption on the face, neck, or other areas exposed to sunlight, I consider whether it may signal a photosensitivity reaction based on a medication that makes the skin more vulnerable to the sun’s rays. If I see atopic dermatitis (also known as atopic eczema, a rash) on an itchy child, I inquire about the rest of the common triad—allergy and asthma. If I notice a ring of warts on the finger of a seven-year-old, I also look at his or her lips to see if hand-to-mouth behavior has resulted in the spread of the condition via auto-inoculation. If, when I inspect the back of a nervous character, I note that easier-to-reach areas have multiple scratch marks in different stages of healing amid a forest of erratic depigmentation, but that the harder-to-reach center of the back is untouched, I shift my diagnostic weight to self-induced neurodermatitis, pathologic skin picking in the absence of any underlying skin disease.
Some of these skin diseases may have protective utility. Psoriasis, for example, may have a hidden adaptive function that carries a genetic survival advantage. If the same genes that trigger psoriasis also control the intensity of response to bacterial invasion, then perhaps the combined one-two punch of an enhanced inflammatory response and thickened keratin layer have given those with the psoriasis-predisposing genome a survival advantage. The natural process of desquamation, where the skin rids itself of excess layers of keratin, is heightened in psoriasis and may provide a helpful response to discourage colonization of the skin’s surface by undesirable microbes and maintain integrity of the skin by shedding faster than colonization can get traction.
Other protective roles for psoriasis can be seen with cutaneous tuberculosis, a disease that can bring on horrible facial destruction. Psoriasis first came to widespread attention in the medical community in the mid-nineteenth century, coincident with a high prevalence of cutaneous (as well as systemic) tuberculosis. As many researchers have reported, cases of patients with both skin diseases were essentially absent. It may be that psoriatic carriers are protected from tuberculosis, or have a survival edge against the more disfiguring cutaneous tuberculosis. If the psoriasis carrier could be protected against tuberculosis, the predisposing psoriasis genotype could survive. Trials and research with the new biologic drugs for psoriasis have proved that psoriasis patients have highly activated immune systems. And one of the main contraindications for the use of any psoriasis-halting biologic is an active systemic tuberculosis infection—in this case, healing patients’ psoriasis might actually worsen their tuberculosis.
Dermatology includes pattern recognition as a primary detection tool, and changes in morphology and distribution of lesions on the body are part of each exam. New growths arise and old ones change form, and infections like candidiasis, from a yeast, erupt in locations where and when they find an opportunity for survival. In a similar fashion, you may notice during a walk in the woods a new flower blooming or pay attention to which species of bird frequents a certain oak or elm. Or you may come across a tree down on the side of the trail and decaying, and note that the way the bracket fungi are oriented on the trunk tells you how long the tree has been nonvertical. As with each observation in nature, ecological abnormalities involving changes on the skin due to invasions, disturbances, and imbalances are an integral part of observing skin diseases and providing treatments.
The skin is an amazing, versatile organ and science discovers more about its magic every day. As you read on, you will understand more about the wonders of our covering and what can happen when it gets violated or reflects an underlying problem. You may even pick up a clue or two on how to save your skin.
CHAPTER TWO
CARE AND PROTECTION OF THE SKIN
Pull down thy vanity, it is not man
Made courage, or made order, or made grace,
Pull down thy vanity, I say pull down.
Learn of the green world what can be thy place
In scaled invention or true artistry,
Pull down thy vanity . . .
The green casque has outdone your elegance.
Ezra Pound, “Canto LXXXI”
As soon as I walked in the room to introduce myself to Guillermo, I knew he represented a challenge of long duration. Populating his face and neck were at least fifteen easily recognizable skin cancers spread out in odd arrangements and patterns. He had one of the worst collective cases of these cancers that I had ever seen. None of them were immediately life threatening, but the disfigurement was horrible. “I have most of these many years,” he said in halting English. “My family tell me I need to get them off.”
“Your family is right,” I said.
Guillermo spent his first fifty years in Cuba, a country with a poor record of skin cancer prevention. In my own sampling, many of my worst skin cancer patients have been from Cuba. And Guillermo had not fared much better after emigrating, as he had exchanged one tropical country for another. Since arriving in Florida five years ago, he had done little to protect himself from further skin insult and injury.
What’s more, our skin cancer prevention program in the United States is not much better than that of Cuba. According to the National Cancer Institute, 40–50 percent of Americans who live to age sixty-five will have skin cancer at least once.
FROM SUN GODS TO TANNING SALONS
Why does our skin get darker over time and exposure to the sun? The main reason is the oxidative stress placed on melanin as it interacts with ultraviolet light, protecting us from dangerous rays.
Melanocytes live in the bottom layer of the epidermis, just above the dermis, and manufacture melanin from an amino acid, tyrosin, with the help of an enzyme, tyrosinase. Exposures of five to ten minutes of sunshine do not bring on tan, but longer than that will initiate a process called melanogenesis. In melanogenesis, ultraviolet (UV) light stimulates the production of melanin in the form of insoluble melanosomes that surround the epidermal cells, which move up to the surface of the skin and result in a tan.
Though people with dark skin and people with light skin have the same number of melanocytes, the way the melanin is distributed and produced is quite different. Darker skin contains more melanin, which protects against ultraviolet radiation and damage to DNA. For this reason it is rare to see skin cancer in African Americans, though I recently saw an African American patient with early skin cancer on his chest. Research by Gloster and Neal, published in 2006, states that the incidence of skin cancer in African Americans is approximately 3 cases per 100,000 people; among European Americans it is 234 cases per 100,000 people. For both African Americans and European Americans, the primary risk factor is chronic UVB exposure.
Many societies today value the look of a dark tan, causing many people to expose themselves to high levels of UV radiation. But no safe tan exists; all tanning is another form of burning.
A quote that has been erroneously attributed to Kurt Vonnegut, but in fact was written by newspaper columnist Mary Schmidt, captures some of the importance of protecting skin from the sun. According to the urban legend, Vonnegut was asked to be the guest speaker for a prestigious college’s commencement exercise, and told the graduating class only: “Wear sunscreen. If I could offer you only one tip for the future, sunscreen would be it. The long-term benefits of sunscreen have been proved by scientists, whereas the rest of my advice has no basis more reliable than my own meandering experience. . . . Advice is a form of nostalgia. Dispensing it is a way of fishing the past from the disposal, wiping it off, painting over the ugly parts and recycling it for more than it’s worth. But trust me on the sunscreen.”
During my childhood summers in Michigan, where I grew up less than an hour from the beach, I cherished the sun. I recall the smell of baby oil mixed with the thin toasty smell of heated skin. I savored the precious two months when I could actually lay in the sun with scant clothing, the memories of giant