What is dermatology? |

Science and Profession

Dermatology is the subfield of medicine that deals with diseases of the skin. Some disorders affecting the hair and fingernails may also fall under this category.

Dermatological study requires attention to three distinct layers of the skin, each of which can be affected differently by different disorders. The deepest layer is the subcutaneous tissue, where fat is formed and stored. It is also here that the deeper hair follicles and sweat glands originate. Blood vessels and nerves pass from this layer to the dermis. The dermis is mainly connective tissue that contains the oil-producing, or sebaceous, glands and shorter hair follicles. On the surface of the skin is the epidermis, which is itself multilayered. The innermost basal layer is made up of specialized keratin- and melanin-forming cells, whereas the outermost, horny cell layer consists of keratinized dead cells.

The diagnosis of apparent skin disease requires dermatologists to determine whether symptomatic sores, or lesions, are primary (the original symptoms of suspected disease) or secondary (such as infection or irritation caused by scratching, which may overshadow the original disorder). Dermatologists are trained to recognize categories of lesions and to determine whether they represent actual diseases or relatively common disorders characteristic of age, or even genetic predispositions. The most common categories of lesions include vesicles, bullae, and crusts; scaling; keratosis; lichenification; pustules; atrophy; and tumors.

Vesicles and bullae are bubblelike eruptions filled with clear serous fluid. As primary lesions, they are often the symptoms of diseases such as chickenpox and herpes zoster. Crusts are formed by tissue fluid that remains in a dried form after the rupture of microscopic vesicles.

Scaling is noticeably different from crusting. These flakes on the surface of the skin may represent a subsiding stage of earlier inflammation. Scaling may be a secondary lesion associated with psoriasis. Keratoses are rough lesions that show strongly adherent (not loose) flaking. Lichenification involves a thickening of the epidermis, with a more pronounced visibility of lined patterns on the skin surface. Pustules are lesions filled with pus, which serves as a growth medium for microorganisms. Atrophy involves shrinkage of skin tissues, creating in some cases visible depressions in the area of the lesion. The last category of primary lesions, tumors, may be found either on the surface of or underneath the skin. Tumorous growths can signal a condition as benign as seborrheic keratosis (the appearance of thick scales in isolated spots, particularly as age advances) or as serious as one of several forms of skin cancer.

Secondary lesions appear as the primary, or causal, skin disorder progresses, creating different symptoms in the secondary stage. Examples of secondary lesions include scales (dandruff and psoriasis), crusts (impetigo), ulcers (advanced syphilis), and scarring, the growth of connective tissue that actually replaces damaged tissues following burns or other traumatic injuries.

In addition to these general categories of lesions associated with dermatological diseases, a number of localized problems in blood flow—called vascular nevoid lesions, or birthmarks—may be visible at or soon after birth. Dermatologists assume that some of these lesions may be caused by genetic factors. The most common vascular nevi categories are nevus flammeus (port-wine stain), a purple discoloring of the skin resulting from dilated dermal vessels, and capillary hemangioma (strawberry mark), which begins as a bruiselike lesion but soon grows into a protruding mass. Unlike port-wine stains, which remain throughout the individual’s lifetime unless they are removed through laser surgery, strawberry marks will usually subside and disappear on their own, leaving at most visible puckering of the skin. Unless there are complications (such as ulceration), treatment is usually simple, consisting of the application of elastic bandages to maintain constant pressure, thus reducing the distortion caused by the rapid expansion of skin tissue in a localized area.

Probably the most commonly recognized dermatological disorder, acne, usually occurs among adolescents and young adults. Although this problem is likely to occur as part of the normal process of maturation, lack of proper care of acne may cause complications and lifelong scarring. Acne, as with equally common cases of seborrheic dermatitis (which causes dandruff), afflicts those areas of the body where oil gland secretions are plentiful and where many forms of bacteria are present on the skin (mainly the face, neck, and upper trunk). The points of lesion for acne are always specific: the hair follicles that are so numerous in these areas of the body. Two phenomena, so-called blackheads and the pimples associated with acne, occur when the normal draining of follicle secretions is blocked in a sac called a comedo. Blackheads occur when the residue trapped in the comedo—keratin, sebum, and various microorganisms—becomes chemically oxidized. When conditions associated with acne appear, an increase in bacterial growth within the comedones produces characteristic pimples which, if traumatized by scratching or picking, may burst, leading to the possibility of further infection. There is no way to prevent acne from appearing, but dermatological therapy to soothe the effects of advanced cases may be recommended.

Another relatively benign but persistently insoluble dermatological problem, the appearance of warts, occurs most often among the middle-aged or older segment of the adult population. Modern dermatological research dating from the 1960s has determined that warts are associated with particular viral strains (papillomaviruses). At least four subtypes have been associated with the appearance of warts on the human body. Warts may vary greatly in appearance—from plantar warts, which grow well below the skin surface and exhibit a drier consistency; to plane warts, which are even with the skin surface; to a very visible brownish and moist lump, which is often found on the face or hands. All warts are localized viral infections that destroy the normal skin tissue in the area of infection. Despite their common occurrence—dermatologists experience a high rate of patient demand for their removal—warts have always carried a certain social stigma. As viruses, they may be transferred to others through contact, particularly if the lesion is an open one.

The term “seborrheic dermatitis” can refer to the recurrent and common problem of dandruff (redness and scaling mainly in skin areas where body hair is present). Like acne, seborrheic dermatitis is more a condition resulting from secretion imbalances and chemical reactions affecting the skin than an actual disease. Dermatological complications arise when excessive scratching of sensitive areas causes secondary lesions to form.

Beyond these categories of common skin disorders are far more serious diseases that require professional dermatological treatment. For example, psoriasis, although varying in possible locations all over the body (including the hands and feet), seems to share symptoms with seborrheic dermatitis, specifically the flaking away of dry skin. What begins as limited patches of flaking, usually on elbows or in the armpits, however, may spread rapidly and have traumatic effects. Dermatologists usually associate psoriasis with stress and anxiety. When irritations are limited in scope, treatment through topical medications—including corticosteroids, salicylic acid, and coal tar—may be successful. Advanced cases may demand systemic treatment with more sophisticated drugs. Phototherapy (light therapy) may also be used for treatment.

Herpes simplex is another common viral infection that leads directly to surface lesions that may be communicable, in this case cold sores. As with warts, folk knowledge has it that improper hygienic practices lead to the much more virulent eruptions associated with herpes simplex. Medical observations have shown, however, that various factors may unleash a dermatological reaction from latent viral sources in an individual. A herpes simplex reaction to increased levels of exposure to sunlight is a good example. On the other hand, many cases of herpes simplex occur in both the male and female genital areas. Although these eruptions are not necessarily connected with much more serious sexually transmitted diseases, their communicability is clearly associated with levels of hygiene in intimate sexual contact. Whatever the cause of herpes simplex, its highly contagious nature may demand dermatological attention to avoid more serious complications. Any occurrence of herpes simplex inflammation near a vital organ, for example, must be treated immediately to prevent the spread of viral infection, particularly in the area surrounding the eyes.

Herpes zoster, commonly referred to as shingles, is thought to be a recurrence in the adult years of a common viral infection that most people experience at an earlier age: chickenpox. The persistence of the symptoms of shingles among adults, however, is not comparable to the mild effect of the virus during childhood. The appearance of painful lesions, usually but not always in the trunk area, may come after a short period of tingling. Although inflammation may pass, many elderly patients, especially those suffering from systemic diseases such as diabetes mellitus, are plagued by continuous long-term discomfort. In addition to discomfort, there may be (as in herpes simplex) a danger of complications if the area of inflammation is close to vulnerable tissues or key organs, such as the eyes or ears. In cases where lesions may affect the eyes, dermatologists must go beyond topical treatment to enhance the healing process. Additional emergency therapy may include corticosteroid treatments.

Diagnostic and Treatment Techniques

The diagnosis of specific dermatoses, or potentially serious skin diseases, may or may not require cutaneous biopsies; because their symptoms are not shared by other diseases, a diagnosis can often be made by observation alone. Less easily recognized problems include lichen planus, an uncommon chronic pruritic disease; such potentially dangerous bullous diseases as pemphigus vulgaris, which is characterized by flat-topped papules on the wrists and legs that resemble poison ivy reactions; and skin cancer. Such conditions usually require biopsy to ensure that a mistaken diagnosis does not lead to the wrong treatment. Several methods of biopsy are employed, according to the nature of the lesion under examination. For example, the cutaneous punch technique, which utilizes a special surgical tool that penetrates to about four millimeters, may not be appropriate if the lesion is close to the surface. In this case, either curettage (scraping) or shave biopsy (cutting a layer corresponding to the thickness of the lesion) may be used in combination with the cutaneous punch method.

The total number of dermatoses that can be diagnosed is far too great for review here. The conditions that are most commonly treated, however, range from mildly serious but clearly irritating lesions such as acne or warts to much more serious phenomena such as psoriasis and lupus erythematosus. Several early and potentially dangerous conditions, such as basal cell carcinoma, may deteriorate into fatal skin cancers.

Dermatologists classify serious skin diseases under several key divisions. Pruritic dermatoses are characterized by itching. Vascular dermatoses, including several categories of urticaria, are all characterized by sudden outbreaks of papules—some temporary in their irritation and therefore merely disorders, as with hives as a reaction to poison ivy or medicines such as penicillin; and others more serious, such as swelling of the glottis, which may accompany angioneurotic edema. Papulosquamous dermatoses include psoriasis and lichen planus, both localized irritations that involve redness and flaking. In addition to these categories of dermatoses, a wide variety of common dermatologic viruses demand special medical attention because they are socially communicable. These include herpes simplex and herpes zoster. Other serious viruses affecting the skin, such as smallpox and measles, have been controlled by preventive vaccinations. Impetigo, once common during childhood in certain environments, is a bacterial infection, not a viral one. One formerly lethal sexually transmitted disease is syphilis, a form of spirochetal infection. Although far from eradicated, syphilis has been treatable through the use of benzathine penicillin since the mid-twentieth century.

The most serious challenge to dermatologists is the early diagnosis and treatment of skin cancer. The most common forms of skin cancer are basal cell epithelioma, which originates in the epidermis, often as a result of excessive exposure to the sun, and squamous cell carcinoma, which may affect the epidermis or mucosal surfaces (the inside of the mouth or throat). Early diagnosis of both types is essential to prevent metastasis (spreading). The most dangerous skin cancer is malignant melanoma , which may reveal itself through changes in size or color of a body mark such as a mole. This cancer can metastasize very rapidly and endanger the life of the patient.

Possible treatments for different types of skin disease vary considerably. Surgical operations, although certainly not unknown, tend to be associated with more extreme disorders, most notably skin cancer. In such cases, it is usually not the dermatologist but a specialized surgeon who performs the procedure.

The most common treatments used by dermatologists involve the application of various pharmaceutical preparations directly to the surface of the skin. For the treatment of common skin disorders, dermatologists may choose between a variety of medications.

The effect of antipruritic agents (menthol, phenol, camphor, or coal tar solutions) is to reduce itching. Keratoplastic agents (salicylic acid) and keratolytic agents (stronger doses of salicylic acid, resorcinol, or sulfur) affect the relative thickness or softness of the horny layer of the skin. They are associated with the treatment of diseases or disorders characterized by flaking.

Antieczematous agents, including coal tar solutions and hydrocortisone, halt oozing from vesicular lesions. By far the most commonly used drugs in dermatology are antiseptics which, according to their classification, control or kill bacteria, fungi, and viruses. Ointments to combat viral infections are much less common on the pharmaceutical market; however, some are available, mainly for the treatment of infection by herpes labialis (cold sores), herpes zoster (shingles), or varicella zoster (chickenpox).

These and many other topical applications may be only the first steps, however, in soothing the irritating side effects of more serious or chronically persistent dermatological diseases. Doctors may turn to more active therapies to treat specific ailments, beginning with the general category of electrosurgery, of which there are five specialized subtreatments: electrodesiccation, or the drying of tissues; electrocoagulation, which involves more intense heat; electrocautery, the actual burning of tissues; electrolysis, which produces the cauterization of lesions by chemical reaction; and electrosection, or the removal of tissues by cutting, achieved by the focus of electrical currents produced by various forms of vacuum tubes. By the 1990s, rapid progress in laser beam technology—particularly the carbon dioxide laser, which is a beam of infrared electromagnetic energy with an almost infinitesimal wavelength of 10,600 nanometers—began to replace some of these time-tested methods in cases in which electrosurgery had been commonplace for almost half a century.

Other modes of treatment that penetrate the subsurface layers of the skin include radiation therapy and cryosurgery, which is the immediate freezing of tissues by application of agents such as solid carbon dioxide (below -78.5 degrees Celsius) or liquid nitrogen (below -195.8 degrees Celsius). Another treatment option is phototherapy, or light therapy, in which skin is exposed to ultraviolet light for a set amount of time. These methods are used to treat conditions ranging from psoriasis and pruritic dermatoses to skin cancer.

Perspective and Prospects

One common feature—visible body surface symptoms—means that the medical identification and attempted treatment of human skin diseases can be traced to almost all cultures in all historical periods. An outstanding example of ancient peoples’ concerns for eruptions on the skin can be found in the Old Testament or Talmud in Leviticus. In this text, however, as well as in many medieval texts, one sees that a variety of skin diseases tended to be classified as leprosy. The physical location of skin lesions often determined the results of very general attempts at diagnosis.

It was not until the last quarter of the eighteenth century that Viennese physicians ushered in what could be called the first phase of scientific study of the skin and its disorders, or dermatology. This early Viennese school insisted on the study of the morphological nature of the lesions. Until this time, physicians had grouped skin diseases according to their appearance in different places on the body. By the mid-nineteenth century another Austrian, Ferdinand von Hebra, made considerable progress in classifying skin diseases.

Because so many lesions of the skin could potentially lead to diagnoses of sexually transmitted diseases, early generations of dermatologists concentrated most of their emphasis in this area. Discovery of a treatment for syphilis in the early twentieth century freed researchers to diversify their physiological investigations, opening the field to broader applications of biochemistry for treatment of different skin conditions, a field developed by the American doctor Stephen Rothman in the 1930s. Some categories, such as fungal diseases, were brought under control by treatments that were developed fairly quickly. By the second half of the century, dermatologists could alleviate most of the complications caused by psoriasis. Then, during the last quarter of the twentieth century, impressive advances in the discovery and patenting of sophisticated drugs brought most of the major dermatological diseases, including those caused in large part by nervous stress, under general control.

Although the treatment of life-threatening diseases, particularly skin cancers, continues to fall short of guaranteed cures, early recognition of their symptoms has steadily increased patients’ chances for survival.

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