How to Use this Book

The Color Atlas and Synopsis of Clinical Dermatology is proposed as a “field guide” to the recognition of skin disorders and their management. The skin is a treasury of important lesions that can usually be recognized clinically. Gross morphology in the form of skin lesions remains the hard core of dermatologic diagnosis. Therefore, this text is accompanied by more than 1000 color photographs illustrating skin diseases, skin manifestation of internal diseases, infections, tumors, and incidental skin findings in otherwise well individuals. We have endeavored to include information relevant to gender dermatology and a large number of images showing skin disease in different ethnic populations. Important dermoscopic issues, biologic therapy, and artificial intelligence have been highlighted. This Atlas covers the entire field of clinical dermatology but does not include very rare syndromes or conditions. With respect to these, the reader is referred to another McGraw Hill publication: Fitzpatrick’s Dermatology, 9th edition, 2019, edited by Sewon Kang, Masayuki Amagai, Anna L. Bruckner, Alexander H. Enk, David J. Margolis, Amy J. McMichael, and Jeffrey S. Orringer.

This text is intended for all physicians and other health care providers, including medical students, dermatology residents, internists, oncologists, and infectious disease specialists dealing with diseases with skin manifestations. For nondermatologists, it is advisable to start with “Approach to Dermatologic Diagnosis” and “Outline of Dermatologic Diagnosis” to familiarize themselves with the principles of dermatologic nomenclature and lines of thought.

The Atlas is organized into four parts, subdivided into 35 sections, and there are four short appendices. Each section has a color label that is reflected by the bar on the top of each page. This is to help the reader find his or her bearings rapidly when leafing through the book. Each disease is labeled with the respective ICD10 codes.

There are two distinct clinical situations regarding the nature of skin changes:

1. The skin changes are incidental findings in well and ill individuals noted during the routine general physical examination:

   • “Bumps and blemishes”: many asymptomatic lesions that are medically inconsequential may be present in well and ill persons, and may not be the reason for their visit to the physician; every general physician should be able to recognize these lesions to differentiate them from asymptomatic but important, e.g., malignant, lesions.

   • Important skin lesions not noted by the patient but that must not be overlooked by the physician: e.g., dysplastic nevi, melanoma, basal cell carcinoma, squamous cell carcinoma, café-au-lait macules in von Recklinghausen disease, and xanthomas.

2. The skin changes are the chief complaint of the patient:

   • “Minor” problems: e.g., localized itchy rash, “rash,” rash in groin, nodules such as common moles and seborrheic keratoses.

   • “4-S”: serious skin signs in sick patients.

SERIOUS SKIN SIGNS IN SICK PATIENTS

• Generalized red rash with fever:

  • Viral exanthems.

  • Rickettsial exanthems.

  • Drug eruptions.

  • Bacterial infections with toxin production.

• Generalized red rash with blisters and prominent mouth lesions:

  • Erythema multiforme (major).

  • Toxic epidermal necrolysis.

  • Pemphigus.

  • Bullous pemphigoid.

  • Drug eruptions.

• Generalized red rash with pustules:

  • Pustular psoriasis (von Zumbusch).

  • Drug eruptions.

• Generalized rash with vesicles:

  • Disseminated herpes simplex.

  • Generalized herpes zoster.

  • Varicella.

  • Drug eruptions.

• Generalized red rash with scaling over whole body:

  • Exfoliative erythroderma.

• Generalized wheals and soft-tissue swelling:

  • Urticaria and angioedema.

• Generalized purpura:

  • Thrombocytopenia.

  • Purpura fulminans.

  • Drug eruptions.

• Generalized purpura that can be palpated:

  • Vasculitis.

  • Bacterial endocarditis.

• Multiple skin infarcts:

  • Meningococcemia.

  • Gonococcemia.

  • Disseminated intravascular coagulopathy.

• Localized skin infarcts:

  • Calciphylaxis.

  • Atherosclerosis obliterans.

  • Atheroembolization.

  • Warfarin necrosis.

  • Antiphospholipid antibody syndrome.

• Facial inflammatory edema with fever:

  • Erysipelas.

  • Lupus erythematosus.

  • Dermatomyositis.

In contrast to other fields of clinical medicine, patients should be examined before a detailed history is taken because patients can see their lesions and thus often present with a history that is flawed with their own interpretation of the origin or causes of the skin eruption. Also, diagnostic accuracy is higher when objective examination is approached without preconceived ideas. However, a history should always be obtained but if taken during or after the visual and physical examination, it can be streamlined and more focused following the objective findings. Thus, recognizing, analyzing, and properly interpreting skin lesions are the sine qua non of dermatologic diagnosis.

PHYSICAL EXAMINATION

Appearance Uncomfortable, “toxic,” well.

Vital Signs Pulse, respiration, temperature.

Skin: “Learning to Read” The entire skin should be inspected and this should include mucous membranes, genital and anal regions, as well as hair and nails and peripheral lymph nodes. Reading the skin is like reading a text. The basic skin lesions are like the letters of the alphabet: their shape, color, margination, and other features combined will lead to words, and their localization and distribution to a sentence or paragraph. The prerequisite of dermatologic diagnosis is thus the recognition of (1) the type of skin lesion, (2) the color, (3) margination, (4) consistency, (5) shape, (6) arrangement, and (7) distribution of lesions.

Recognizing Letters: Types of Skin Lesions

• Macule (Latin: macula, “spot”) A macule is a circumscribed area of change in skin color without elevation or depression. It is thus not palpable. Macules can be well defined and ill defined. Macules may be of any size or color (Fig. I-1). White, as in vitiligo; brown, as in café-au-lait spots; blue, as in dermal melanosis; or red, as in permanent vascular abnormalities such as port-wine stains or capillary dilatation due to inflammation (erythema). Pressure of a glass slide (diascopy) on the border of a red lesion detects the extravasation of red blood cells. If the redness remains under pressure from the slide, the lesion is purpuric, that is, results from extravasated red blood cells; if the redness disappears, the lesion is due to vascular dilatation. A rash consisting of macules is called a macular exanthem.

• Papule (Latin: papula, “pimple”) A papule is a superficial, elevated, solid lesion, generally considered <0.5 cm in diameter. Most of it is elevated above, rather than deep within, the plane of the surrounding skin (Fig. I-2). A papule is palpable. It may be well defined or ill defined. In papules, the elevation is caused by metabolic or locally produced deposits, by localized cellular infiltrates, inflammatory or noninflammatory, or by hyperplasia of local cellular elements. Superficial papules are sharply defined. Deeper dermal papules have indistinct borders. Papules may be dome-shaped, cone-shaped, or flat-topped (as in lichen planus) or consist of multiple, small, closely packed, projected elevations that are known as a vegetation (Fig. I-2). A rash consisting of papules is called a papular exanthem. Papular exanthems may be grouped (“lichenoid”) or disseminated (dispersed). Confluence of papules leads to the development of larger, usually flat-topped, circumscribed, plateau-like elevations known as plaques (French: plaque, “plate”). See the following.

• Plaque A plaque is a plateau-like elevation above the skin surface that occupies a relatively large surface area in comparison with its height above the skin (Fig. I-3). It is usually well defined. Frequently, it is formed by a confluence of papules, as in psoriasis. Lichenification is a less well-defined large plaque where the skin appears thickened and the skin markings are accentuated. Lichenification occurs in atopic dermatitis, eczematous dermatitis, psoriasis, lichen simplex chronicus, and mycosis fungoides. A patch is a barely elevated plaque—a lesion fitting between a macule and a plaque—as in parapsoriasis or Kaposi sarcoma.

• Nodule (Latin: nodulus, “small knot”) A nodule is a palpable, solid, round, or ellipsoidal lesion that is larger than a papule (Fig. I-4) and may involve the epidermis, dermis, or subcutaneous tissue. The depth of involvement and the size differentiate a nodule from a papule. Nodules result from inflammatory infiltrates, neoplasms, or metabolic deposits in the dermis or subcutaneous tissue. Nodules may be well defined (superficial) or ill defined (deep); if localized in the subcutaneous tissue, they can often be better felt than seen. Nodules can be hard or soft upon palpation. They may be dome-shaped and smooth or may have a warty surface or crater-like central depression.

• Wheal A wheal is a rounded or flat-topped, pale red or white papule or plaque that is characteristically evanescent, disappearing within 24 to 48 h (Fig. I-5). It is due to edema in the papillary body of the dermis. If the edema is very pronounced, it will compress the dilated capillaries and the wheal will turn white (Fig. 1-5). Wheals may be round, gyrate, or irregular with pseudopods—changing rapidly in size and shape due to shifting papillary edema. A rash consisting of wheals is called an urticarial exanthema or urticaria.

• Vesicle-Bulla (Blister) (Latin: vesicula, “little bladder”; bulla, “bubble”) A vesicle (<0.5 cm) or a bulla (>0.5 cm) is a circumscribed, elevated, superficial cavity containing fluid (Fig. I-6). Vesicles are dome-shaped (as in contact dermatitis, dermatitis herpetiformis), umbilicated (as in herpes simplex), or flaccid (as in pemphigus). Often the roof of a vesicle/bulla is so thin that it is transparent, and the serum or blood in the cavity can be seen. Vesicles containing serum are yellowish; those containing blood from red to black. Vesicles and bullae arise from a cleavage at various levels of the superficial skin; the cleavage may be subcorneal or within the epidermis (i.e., intraepidermal vesication) or at the epidermal–dermal interface (i.e., subepidermal), as in Figure I-6. Since vesicles/bullae are always superficial they are always well defined. A rash consisting of vesicles is called a vesicular exanthem; a rash consisting of bullae a bullous exanthem.

• Pustule (Latin: pustula, “pustule”) A pustule is a circumscribed superficial cavity of the skin that contains a purulent exudate (Fig. I-7), which may be white, yellow, greenish-yellow, or hemorrhagic. Pustules thus differ from vesicles in that they are not clear but have a turbid content. This process may arise in a hair follicle or independently. Pustules may vary in size and shape. Pustules are usually dome-shaped, but follicular pustules are conical and usually contain a hair in the center. The vesicular lesions of herpes simplex and varicella zoster virus infections may become pustular. A rash consisting of pustules is called a pustular exanthem.

• Crusts (Latin: crusta, “rind, bark, shell”) Crusts develop when serum, blood, or purulent exudate dries on the skin surface (Fig. I-8). Crusts may be thin, delicate, and friable or thick and adherent. Crusts are yellow when formed from dried serum; green or yellow-green when formed from purulent exudate; or brown, dark red, or black when formed from blood. Superficial crusts occur as honey-colored, delicate, glistening particulates on the surface and are typically found in impetigo (Fig. I-8). When the exudate involves the entire epidermis, the crusts may be thick and adherent, and if it is accompanied by necrosis of the deeper tissues (e.g., the dermis), the condition is known as ecthyma.

• Scales (squames) (Latin: squama, “scale”) Scales are flakes of stratum corneum (Fig. I-9). They may be large (like membranes), tiny [(like dust)], pityriasiform (Greek: pityron, “bran”), adherent, or loose. A rash consisting of papules with scales is called a papulosquamous exanthem.

• Erosion An erosion is a defect only of the epidermis, not involving the dermis (Fig. I-10); in contrast to an ulcer, which always heals with scar formation (see the following), an erosion heals without a scar. An erosion is sharply defined, red, and oozes. There are superficial erosions, which are subcorneal or run through the epidermis, and deep erosions, the base of which is the papillary body (Fig. I-10). Except physical abrasions, erosions are always the result of intraepidermal or subepidermal cleavage and thus of vesicles or bullae.

• Ulcer (Latin: ulcus, “sore”) An ulcer is a skin defect that extends into the dermis or deeper (Fig. I-11) into the subcutis and always occurs within pathologically altered tissue. An ulcer is therefore always a secondary phenomenon. The pathologically altered tissue that gives rise to an ulcer is usually seen at the border or the base of the ulcer and is helpful in determining its cause. Other features helpful in this respect are whether borders are elevated, undermined, hard, or soggy; location of the ulcer; discharge; and any associated topographic features, such as nodules, excoriations, varicosities, hair distribution, presence or absence of sweating, and arterial pulses. Ulcers always heal with scar formation.

• Scar A scar is the fibrous tissue replacement of the tissue defect by previous ulcer or a wound. Scars can be hypertrophic and hard (Fig. I-12) or atrophic and soft with a thinning or loss of all tissue compartments of the skin (Fig. I-12).

• Atrophy This refers to a diminution of some or all layers of the skin (Fig. I-13). Epidermal atrophy is manifested by a thinning of the epidermis, which becomes transparent, revealing the papillary and subpapillary vessels; there are loss of skin texture and cigarette paper-like wrinkling. In dermal atrophy, there is loss of connective tissue of the dermis and depression of the lesion (Fig. I-13).

• Cyst A cyst is a cavity containing liquid or solid or semisolid (Fig. I-14) materials and may be superficial or deep. Visually it appears like a spherical, most often dome-shaped papule or nodule, but upon palpation it is resilient. It is lined by an epithelium and often has a fibrous capsule; depending on its contents it may be skin colored, yellow, red, or blue. An epidermal cyst producing keratinaceous material and a pilar cyst that is lined by a multilayered epithelium are shown in Figure I-14.

Shaping Letters into Words: Further Characterization of Identified Lesions

• Color Pink, red, purple (purpuric lesions do not blanch with pressure with a glass slide [diascopy]), white, tan, brown, black, blue, gray, and yellow. The color can be uniform or variegated.

• Margination Well (can be traced with the tip of a pencil) and ill defined.

• Shape Round, oval, polygonal, polycyclic, annular (ring-shaped), iris, serpiginous (snakelike), umbilicated.

• Palpation Consider (1) consistency (soft, firm, hard, fluctuant, boardlike), (2) deviation in temperature (hot, cold), and (3) mobility. Note presence of tenderness, and estimate the depth of the lesion (i.e., dermal or subcutaneous).

Forming Sentences and Understanding the Text: Evaluation of Arrangement, Patterns, and Distribution

• Number Single or multiple lesions.

• Arrangement Multiple lesions may be (1) grouped: herpetiform, arciform, annular, reticulated (net-shaped), linear, serpiginous (snakelike) or (2) disseminated: scattered discrete lesions.

• Confluence Yes or no.

• Distribution Consider (1) extent: isolated (single lesions), localized, regional, generalized, universal, and (2) pattern: symmetric, exposed areas, sites of pressure, intertriginous area, follicular localization, random, following dermatomes or Blaschko lines.

Table I-1 provides an algorithm showing how to proceed.

HISTORY

Demographics Age, race, sex, and occupation.

History

1. Constitutional symptoms:

   • “Acute illness” syndrome: headaches, chills, feverishness, and weakness.

   • “Chronic illness” syndrome: fatigue, weakness, anorexia, weight loss, and malaise.

2. History of skin lesions. Seven key questions:

   • When ? Onset

   • Where? Site of onset

   • Does it itch or hurt? Symptoms

   • How has it spread (pattern of spread)? Evolution

   • How have individual lesions changed? Evolution

   • Provocative factors? Heat, cold, sun, exercise, travel history, drug ingestion, pregnancy, season

   • Previous treatment(s)? Topical and systemic

3. General history of present illness as indicated by clinical situation, with particular attention to constitutional and prodromal symptoms.

4. Past medical history:

   • Operations

   • Illnesses (hospitalized?)

   • Allergies, especially drug allergies

   • Medications (present and past)

   • Habits (smoking, alcohol intake, drug abuse)

   • Atopic history (asthma, hay fever, eczema)

5. Family medical history (particularly of psoriasis, atopy, melanoma, xanthomas, tuberous sclerosis).

6. Social history, with particular reference to occupation, hobbies, exposures, travel, or injecting drug use.

7. Sexual history: history of risk factors of HIV: blood transfusions, IV drugs, sexually active, multiple partners, sexually transmitted disease?

REVIEW OF SYMPTOMS

This should be done as indicated by the clinical situation, with particular attention to possible connections between signs and disease of other organ systems (e.g., rheumatic complaints, myalgias, arthralgias, Raynaud phenomenon, and sicca symptoms).

SPECIAL TECHNIQUES USED IN CLINICAL EXAMINATION

Magnification with hand lens. To examine lesions for fine morphologic detail, it is necessary to use a magnifying glass (hand lens) (7×) or a binocular microscope (5× to 40×). Magnification is especially helpful in the diagnosis of lupus erythematosus (follicular plugging), lichen planus (Wickham striae), basal cell carcinomas (translucence and telangiectasia), and melanoma (subtle changes in color, especially gray or blue); this is best visualized after application of a drop of mineral oil. Use of the dermatoscope is discussed below (see “Dermoscopy”).

Oblique lighting of the skin lesion, done in a darkened room, is often required to detect slight degrees of elevation or depression, and it is useful in the visualization of the surface configuration of lesions and in estimating the extent of the eruption.

Subdued lighting in the examining room enhances the contrast between circumscribed hypopigmented or hyperpigmented lesions and normal skin.

Wood lamp (ultraviolet long-wave light, “black” light) is valuable in the diagnosis of certain skin and hair diseases and of porphyria. With the Wood lamp (365 nm), fluorescent pigments and subtle color differences of melanin pigmentation can be visualized. The Wood lamp also helps to estimate variation in the lightness of lesions in relation to the normal skin color in both dark-skinned and fair-skinned persons; e.g., the lesions seen in tuberous sclerosis and tinea versicolor are hypomelanotic and are not as white as the lesions seen in vitiligo, which are amelanotic. Circumscribed hypermelanosis, such as a freckle and melasma, is much more evident (darker) under the Wood lamp. By contrast, dermal melanin does not become accentuated under the Wood lamp. Therefore, it is possible to localize the site of melanin by use of the Wood lamp. However, this is more difficult or not possible in patients with brown or black skin.

Wood lamp is particularly useful in the detection of the fluorescence of dermatophytosis in the hair shaft (green to yellow) and of erythrasma (coral red). A presumptive diagnosis of porphyria can be made if a pinkish-red fluorescence is demonstrated in urine examined with the Wood lamp; addition of dilute hydrochloric acid intensifies the fluorescence.

Diascopy consists of firmly pressing a microscopic slide or a glass spatula over a skin lesion. The examiner will find this procedure of special value in determining whether the red color of a macule or papule is due to capillary dilatation (erythema) or to extravasation of blood (purpura) that does not blanch. Diascopy is also useful for the detection of the glassy yellow-brown appearance of papules in sarcoidosis, tuberculosis of the skin, lymphoma, and granuloma annulare.

Dermoscopy (previously called epiluminescence microscopy). A hand lens with built-in lighting and a magnification of 10× to 30× is called a dermatoscope and permits the noninvasive inspection of deeper layers of the epidermis and beyond. This is particularly useful in the distinction of benign and malignant growth patterns in pigmented lesions. Digital dermoscopy is particularly useful in the monitoring of pigmented skin lesions because images are stored electronically and can be retrieved and examined at a later date to permit comparison quantitatively and qualitatively and to detect changes over time. Digital dermoscopy uses computer image analysis programs that provide (1) objective measurements of changes; (2) rapid storage, retrieval, and transmission of images to experts for further discussion (teledermatology); and (3) extraction of morphologic features for numerical analysis. Dermoscopy and digital dermoscopy require special training.

CLINICAL SIGNS

Darier sign is “positive” when a brown macular or a slightly papular lesion of urticarial pigmentosa (mastocytosis) becomes a palpable wheal after being vigorously rubbed with an instrument such as the blunt end of a pen. The wheal may not appear for 5 to 10 min.

Auspitz sign is “positive” when slight scratching or curetting of a scaly lesion reveals punctate bleeding points within the lesion. This suggests psoriasis, but it is not specific.

The Nikolsky phenomenon is positive when the epidermis is dislodged from the dermis by lateral, shearing pressure with a finger, resulting in an erosion. It is an important diagnostic sign in acantholytic disorders such as pemphigus or the staphylococcal scalded skin (SSS) syndrome or other blistering or epidermonecrotic disorders, such as toxic epidermal necrolysis.

CLINICAL TESTS

Patch testing is used to document and validate a diagnosis of allergic contact sensitization and identify the causative agent. Substances to be tested are applied to the skin in shallow cups (Finn chambers), affixed with a tape and left in place for 24 to 48 h. Contact hypersensitivity will show as a papular vesicular reaction that develops within 48 to 72 h when the test is read. It is a unique means of in vivo reproduction of disease in diminutive proportions, for sensitization affects all the skin and may therefore be elicited at any cutaneous site. The patch test is easier and safer than a “use test” with a questionable allergen, that for test purposes is applied in low concentrations in small areas of skin for short periods of time (see Section 2).

Photopatch testing is a combination of patch testing and UV irradiation of the test site and is used to document photo allergy (see Section 10).

Prick testing is used to determine type I allergies. A drop of a solution containing a minute concentration of the allergen is placed on the skin and the skin is pierced through this drop with a needle. Piercing should not go beyond the papillary body. A positive reaction will appear as a wheal within 20 min. The patient has to be under observation for possible anaphylaxis.

Acetowhitening facilitates detection of subclinical penile or vulvar warts. Gauze saturated with 5% acetic acid (or white vinegar) is wrapped around the glans penis or used on the cervix and anus. After 5 to 10 min, the penis or vulva is inspected with a 10× hand lens. Warts appear as small white papules.

LABORATORY TESTS

Microscopic Examination of Scales, Crusts, Serum, and Hair

Gram stains of smears and cultures of exudates and of tissue minces should be made in lesions suspected of being bacterial or yeast (Candida albicans) infections. Ulcers and nodules require a scalpel biopsy in which a wedge of tissue consisting of all three layers of skin is obtained; the biopsy specimen is divided into one-half for histopathology and one-half for culture. This is minced in a sterile mortar and then cultured for bacteria (including typical and atypical mycobacteria) and fungi.

Microscopic examination for mycelia should be made of the roofs of vesicles or of scales (the advancing borders are preferable) or of the hair in dermatophytoses. The tissue is cleared with 10 to 30% KOH and warmed gently. Hyphae and spores will light up by their birefringence (Fig. 26-25). Fungal cultures with Sabouraud medium should be made (see Section 26).

Microscopic examination of cells obtained from the base of vesicles (Tzanck preparation) may reveal the presence of acantholytic cells in the acantholytic diseases (e.g., pemphigus or SSS syndrome) or of giant epithelial cells and multinucleated giant cells (containing 10 to 12 nuclei) in herpes simplex, herpes zoster, and varicella. Material from the base of a vesicle obtained by gentle curettage with a scalpel is smeared on a glass slide, stained with either Giemsa or Wright stain or methylene blue, and examined to determine whether there are acantholytic or giant epithelial cells, which are diagnostic (Fig. 27-32). In addition, culture, immunofluorescence tests, or polymerase chain reaction for herpes have to be ordered.

Laboratory diagnosis of scabies. The diagnosis is established by identification of the mite, or ova or feces, in skin scrapings removed from the papules or burrows (see Section 28). Using a sterile scalpel blade on which a drop of sterile mineral oil has been placed, apply oil to the surface of the burrow or papule. Scrape the papule or burrow vigorously to remove the entire top of the papule; tiny flecks of blood will appear in the oil. Transfer the oil to a microscopic slide and examine for mites, ova, and feces. The mites are 0.2 to 0.4 mm in size and have four pairs of legs (see Fig. 28-16).

Biopsy of the Skin

Biopsy of the skin is one of the simplest, most rewarding diagnostic techniques because of the easy accessibility of the skin and the variety of techniques for study of the excised specimen (e.g., histopathology, immunopathology, polymerase chain reaction, and electron microscopy).

Selection of the site of the biopsy is based primarily on the stage of the eruption, and early lesions are usually more typical; this is especially important in vesiculobullous eruptions (e.g., pemphigus and herpes simplex), in which the lesion should be no more than 24 h old. However, older lesions (2 to 6 weeks) are often more characteristic in discoid lupus erythematosus.

A common technique for diagnostic biopsy is the use of a 3- to 4-mm punch, a small tubular knife much like a corkscrew, which by rotating movements between the thumb and index finger cuts through the epidermis, dermis, and subcutaneous tissue; the base is cut off with scissors. If immunofluorescence is indicated (e.g., as in bullous diseases or lupus erythematosus), a special medium for transport to the laboratory is required.

For nodules, however, a large wedge should be removed by excision including subcutaneous tissue. Furthermore, when indicated, lesions should be bisected, one-half for histology and the other half sent in a sterile container for bacterial and fungal cultures or in special fixatives or cell culture media, or frozen for immunopathologic examination.

Specimens for light microscopy should be fixed immediately in buffered neutral formalin. A brief but detailed summary of the clinical history and description of the lesions should accompany the specimen. Biopsy is indicated in all skin lesions that are suspected of being neoplasms, in all bullous disorders with immunofluorescence used simultaneously, and in all dermatologic disorders in which a specific diagnosis is not possible by clinical examination alone.