1 - 1 - FUNDAMENTALS OF CLINICAL DERMATOLOGY: MORPHOLOGY AND SPECIAL CLINICAL CONSIDERATIONS Flashcards
when the primary lesion is a circumscribed papule or plaque with scale, it likely falls into what type of reaction pattern?
“papulosquamous” reaction pattern
Differentiate the primary lesions based on size, topography and contents.
Macule, petechiae.
A macule is flat, even with the surface level of surrounding skin or mucous membranes, and perceptible only as an area of color different from the surrounding skin or mucous membrane. Macules are less than 1 cm in size
Patch, fixed drug eruption.
A patch, like a macule, is a flat area of skin or mucous membranes with a different color from its surrounding. Patches are 1 cm or larger in size
Papule, lichen nitidus
A papule is an elevated or depressed lesion less than 1 cm in size, which may be solid or cystic. Among other characteristics, papules may be further described by their topography. Some examples include papules that are sessile, pedunculated, domeshaped, flat-topped, filiform, mammillated, acuminate (conical), or umbilicated
Plaque, psoriasis.
A plaque is a solid plateau-like elevation or depression that has a diameter of 1 cm or larger
Nodule, lymphoma cutis.
A nodule is a palpable lesion greater than 1 cm with a domed, spherical or ovoid shape. They may be solid or cystic. Depending on the anatomic component(s) primarily involved, nodules are of 5 main types: (1) epidermal, (2) epidermal–dermal, (3) dermal, (4) dermal–subdermal, and (5) subcutaneous. Texture is an important additional feature of nodules: firm, soft, boggy, fluctuant, etc. Similarly, different surfaces of nodules, such as smooth, keratotic, ulcerated, or fungating, also help direct diagnostic considerations (Fig. 1-5). Tumor, also sometimes included under the heading of nodule, may be used to describe a more irregularly shaped mass, benign or malignant.
Vesicle, bullous lupus erythematosus. Note brown incipient crusts marking the sites of earlier blisters now ruptured.
A vesicle is a fluid-filled papule smaller than 1 cm (Fig. 1-6), whereas a bulla (blister) measures 1 cm or larger (Fig. 1-7). By definition, the wall is thin and translucent enough to visualize the contents, which may be clear, serous, or hemorrhagic.
Vesicles and bullae arise from cleavage at various levels of the epidermis (intraepidermal) or the dermalepidermal interface (subepidermal), sometimes extending into the dermis. The tenseness or flaccidity of the vesicle or bulla may help determine the depth of the split. However, reliable differentiation requires histopathologic examination of the blister edge.
Pustule, pustular psoriasis.
A pustule is a circumscribed, raised papule in the epidermis or infundibulum containing visible pus. The purulent exudate, composed of leukocytes with or without cellular debris, may contain organisms or may be sterile. The exudate may be white, yellow, or greenish-yellow in color. Pustules may vary in size and, in certain situations, may coalesce to form “lakes” of pus. When associated with hair follicles, pustules may appear conical and contain a hair in the center
macroscopic finding indicating a change in the epidermis, usually the stratum corneum
Scale
Scale may have many different descriptive characteristics, for instance, soft, rough, gritty, bran-like, or micaceous
describes dried fluid on the skin’s surface due to serum, blood, pus, or a combination
crust
When crust is round or oval, it points to the former presence of a vesicle, bulla or pustule (as seen in Fig. 1-6). Linear or angulated crusts are indicative of excoriations. Other specialized types of crust include eschar, which is dry, adherent, and dark red-purple, brown, or black in color and signals skin necrosis (Fig. 1-11), or fibrin, which is a soft, yellow crust on the surface of some ulcers.
thickening and accentuation of the skin lines that results from repeated rubbing or scratching of the skin
Lichenification
It is found primarily in chronic eczematous processes or neurogenic processes (Fig. 1-12).
results in a shiny quality with “cigarette-paper” wrinkling
Atrophy
Atrophy of the dermis results in a depressed lesion.
linear loss of continuity of the skin’s surface or mucosa that results from excessive tension or decreased elasticity of the involved tissue.
fissure
Fissures frequently occur on the palms and soles where the thick stratum corneum is least expandable
Ichthyosiform scale, ichthyosis vulgaris
Scales are regular, polygonal plates arranged in parallel rows or diamond patterns (fish-like, tessellated, Fig. 1-9).
Ostraceous scale, psoriasis.
Large scales may accumulate in heaps, giving the appearance of an oyster shell (ostraceous scale, Fig. 1-10).
The most common types of color on the skin are variations in brown (hyperpigmentation) and red (erythema), which will be discussed in depth below. Other colors and their histopathologic correlations are described in Table 1-5.
Brown color is often representative of ______
Brown color is most often representative of melanin, either within melanocytes or outside of melanocytes. Less frequently, a brown hue also may be caused by deposition of other pigments, cells, or materials in the dermis (such as deposition of hemosiderin, amyloid, or mucin; certain types of inflammation, including inflammation that is granulomatous, histiocytic, plasmacytic, or mixed). Mast cells induce melanin production in the overlying epidermis, often leading to brown color overlying the focus of mast cells in the dermis. Melanin in the epidermis, whether contained within or outside of melanocytes, appears tan to muddy brown; when it is very concentrated, as in some nevi or melanomas or heavily pigmented seborrheic keratoses, it may appear brown-black.
Melanin in the dermis, either within melanocytes or extracellular, may appear ______
brown, gray, or blue
This gray-blue color results from the “Tyndall effect,” named for the 19th-century physicist John Tyndall, who described the preferential transmission of longer wavelengths (blue photospectrum) when particles are suspended in a medium (in this case, melanin or other brown pigment suspended in the dermis).
Oxidized keratin, (within an infundibular cyst, for instance) and foreign pigmentation (such as tattoos) can also exhibit the Tyndall effect when located in the dermis.
Differentiation between epidermal and dermal melanin also can be aided by ___
Wood lamp, which accentuates epidermal but not dermal melanin.
Why do inflammatory diseases or injuries have a brown or graybrown tone?
When the epidermis is inflamed or damaged, melanin often drops to into the dermis. Therefore, many subacute, chronic, or recently resolved epidermal inflammatory diseases or injuries have a brown or graybrown tone. The more constitutive pigment in an individual’s skin, the more prominent these changes will be.
Red color is AKA
Also known as “erythema,” red can have infinite hues. Pale red, pink, or purple may result from inflammation leading to hyperemia (subtle vascular dilation). More saturated red to purple can indicate intense hyperemia or vascular congestion (also called rubor, as seen in erysipelas); even more saturated red to purple hue can result from the either malformed or ectopic blood vessels (Fig. 1-13) or extravasated erythrocytes (petechiae or purpura, see “vascular reaction pattern” below).
True red is often associated with ___
neutrophilic inflammation (as seen in cellulitis or Sweet syndrome)
Figure 1-14 Violaceous Gottron papules, dermatomyositis.
Red-purple color (violaceous erythema, Fig. 1-14) is associated with ____
lymphocytic inflammation (lymphoma cutis, connective tissue disease, interface reactions such as lichen planus)
Figure 1-15 Apple-jelly sign, sarcoidosis.
Granulomatous inflammation may appear red-brown (sarcoidosis, marked by the classis “apple jelly” color seen in Fig. 1-15, or a juvenile xanthogranuloma) to orange or yellow (Fig. 1-16, necrobiosis lipoidica).
Figure 1-16 Yellow, necrobiosis lipoidica diabeticorum.
Ring-shaped; implies that the edge of the lesion has a color and/or texture change that is more prominent on the leading edge than the center (as seen in granuloma annulare, tinea corporis, erythema annulare centrifugum) (Fig. 1-17).
Annular
Figure 1-17 Annular lesion, granuloma annulare.
Coin-shaped; solid circle or oval; usually with uniform morphology from the edges to the center (nummular eczema, plaque-type psoriasis, discoid lupus) (Fig. 1-18).
Round/Nummular/Discoid
Figure 1-18 Nummular lesion, nummular dermatitis.
Arc-shaped; often a result of incomplete formation of an annular lesion (urticaria, subacute cutaneous lupus erythematosus).
Arcuate
Resembling a straight line; often implies an external contactant or Koebner phenomenon has occurred in response to scratching; may apply to a single lesion (such as a scabies burrow, poison ivy dermatitis, or bleomycin pigmentation) or to the arrangement of multiple lesions (as seen in lichen nitidus or lichen planus).
Linear
Net-like or lacy in appearance, with somewhat regularly spaced rings or crossing lines with sparing of intervening skin (as seen in livedo reticularis, cutis marmorata) (Fig. 1-19).
Reticular or Retiform
Figure 1-19 Reticular eruption, livedo racemosa.
Having multiple angulated edges, resembling a star (Fig. 1-11).
Stellate
Figure 1-11 Eschar overlying stellate purpura, calciphylaxis.
Serpentine or snake-like (cutaneous larva migrans, for instance, in which the larva migrates this way and that through the skin in a wandering pattern) (Fig. 1-20).
Serpiginous
Figure 1-20 Serpiginous erythema, jellyfish sting.
Target-like, with a center darker than the periphery. Typical targets (eg, erythema multiforme) have 3 zones: a dark red-purple or dusky center, encircled by a paler pink zone, followed by a rim of darker erythema. Atypical targets have just 2 zones, a dark or dusky center with a paler pink rim. Note that both have a center darker in comparison to the outer zone; if the center is paler than the outer zone, it should be termed “annular” (Fig. 1-21).
Targetoid
Figure 1-21 Atypical targetoid lesions, Stevens-Johnson syndrome due to medication.
Formed from coalescing circles, rings, or incomplete rings (as seen in urticaria, subacute cutaneous lupus erythematosus) (Fig. 1-22).
Polycyclic
Figure 1-22 Polycyclic eruption, pityriasis rosea.
Apple-jelly sign
A yellowish hue is produced from pressure on the lesion with a glass slide.
Noted in granulomatous processes (Fig. 1-15)
Figure 1-15 Apple-jelly sign, sarcoidosis.
Auspitz sign
Pinpoint bleeding at the tops of ruptured capillaries with forcible removal of outer scales from a psoriatic plaque
Not entirely sensitive or specific for psoriasis
Buttonhole sign
A flesh-colored, soft papule feels as though it can be pushed through a “buttonhole” into the skin
Noted in a neurofibroma
Carpet tack sign
Horny plugs at the undersurface of scale removed from a lesion
Noted in lesions of chronic cutaneous lupus
Darier sign
Urticarial wheal produced in a lesion after it is firmly rubbed with a finger or the rounded end of a pen; the wheal, which is strictly confined to the borders of the lesion, may not appear for several minutes
Noted in urticaria pigmentosa and rarely with cutaneous lymphoma or histiocytosis
Pseudo-Darier sign
Transient induration of a lesion or piloerection after rubbing
Noted in congenital smooth muscle hamartoma
Fitzpatrick (dimple) sign
Dimpling of the skin with lateral compression of the lesion with the thumb and index finger produces dimpling as a result of tethering of the epidermis to the dermal lesion
Characteristic of dermatofibroma
Nikolsky sign
Lateral pressure on unblistered skin with resulting shearing of the epidermis
Noted in blistering disorders in which the pathology is above the basement membrane zone; relevant entities include pemphigus vulgaris and toxic epidermal necrolysis
Papulosquamous Reaction Pattern—Common Examples
In papulosquamous eruptions, the primary lesion is a relatively thin or flat-topped papule or plaque with scale. Crust or lichenification is usually not present. Histopathologically, these processes involve the epidermis and superficial to mid-dermis. Individual papules or plaques are typically well demarcated, and there is often normal skin visible between each discrete papule or plaque (Table 1-7).
Eczematous Reaction Pattern—Common Examples
Eczematous eruptions consist of thin erythematous papules and plaques with epidermal change. On the surface of an acute eczematous process, there is enough epidermal spongiosis (edema between keratinocytes) to cause the formation of serous crusting, microvesicles, or sometimes frank bullae. When microvesicles collapse, they form characteristic tiny round crusts often admixed with scale and subtle or overt fissuring. When subacute to chronic, the surface is often dry, scaly, fissured, and/or lichenified from rubbing or scratching. Compared with papulosquamous eruptions, eczematous primary lesions are typically ill demarcated, and individual lesions vary widely in their size and spacing. Because most eczematous eruptions share a common histology, the distribution and history are key in differentiating among them (Table 1-8).
Vesiculobullous Reaction Pattern—Common Examples
Sometimes vesicles and bullae are quite obvious; other times, when all the blisters have ruptured, the clinician must recognize their “footprints”—clues to their recent presence. Because blisters are filled with fluid, when they collapse, they often leave behind round, oval, arcuate, or geographic erosions or crusts. When small ruptured vesicles are grouped together, as in herpes simplex, they form crust with “scalloped” edges. Other subtle clues include erosions with “mauserung” desquamation, a rumpled rim of epidermis hanging from the erosion’s edge, or milia, which can result from healing of deeper blisters (Table 1-9).
Some diseases with prominent surface change defy categorization into papulosquamous, eczematous, or vesculobullous reaction patterns. The astute clinician can recognize an eruption as difficult to characterize and is aware this actually suggests a differential diagnosis in itself. Some examples include scabies, acantholytic diseases (Grover, Darier disease), some drug eruptions, some “id” reactions, and some paraneoplastic conditions.
Dermal “Plus” Reaction Pattern—Common Examples
These are dermally infiltrated papules, nodules or plaques with surface change: hyperkeratotic scale, crust, vesicles, pustules, erosion, or ulceration (Table 1-10).
Macular Reaction Pattern—Common Examples
Macules can derive their color changes from changes in the epidermis or dermis (Table 1-11).
Dermal Reaction Pattern—Common Examples
A dermal reaction pattern is a papule or plaque without surface change where the infiltrative process is in the dermis (Table 1-12).
Subcutaneous Reaction Pattern
Subcutaneous reaction pattern is a deeper papule or plaque, usually without surface change, though occasionally they may ulcerate and crust. The infiltrative or inflammatory process is in the subcutis (Table 1-13).
Purpuric Reaction Pattern—Common Examples
Purpura are red or purple macules, patches, papules, or plaques that result from bleeding into the skin. Because blood has extravasated, they do not blanch when pressure is applied. They may range in color from true red to red-purple or magenta to red-brown (“cayenne pepper”). Purpuric macules are sometimes called “petechiae”; purpuric patches are sometimes called “ecchymoses.” Ecchymosis may also overlie a plaque or nodule from dermal or subdermal hemorrhage, known as hematoma, and may appear yellowgreen when a few days old. Purpuric papules, or “palpable purpura,” typically represent inflammation of small vessels associated with hemorrhage, as in leukocytoclastic vasculitis, a coagulopathy affecting small vessels, as in cryoglobulinemia, or very small emboli. Purpuric plaques represent ischemia, embolism, infarction, intravascular infection, or inflammation of smallmedium or medium vessels, that may lead to necrosis of the overlying epidermis. These can manifest as pink papules (usually medium vessels) or stellate dark purple plaques (Fig. 1-23), and may be accompanied by pink, red, or purple net-like (“retiform”) hyperemia (“livedo”). If the overlying epidermis becomes necrotic, bullae, ulcer, and/or eschar may form at the surface (Table 1-14).
Erythemas
Erythemas are blanching red-pink macules, patches, papules, or plaques, or a combination, usually without surface change. This reaction pattern may be subdivided into morbilliform erythemas, figurate erythemas, urticarial erythemas, and targetoid erythemas (Table 1-15).
pink, blanching macules, papules, or plaques, often exhibiting a characteristic “wheal and flare” appearance, with blanching of the skin surrounding the primary lesion (Fig. 1-24).
Figure 1-24 Urticarial phase, bullous pemphigoid.
Urticarial erythemas
Purpuric plaques represent ischemia, embolism, infarction, intravascular infection, or inflammation of smallmedium or medium vessels, that may lead to necrosis of the overlying epidermis. These can manifest as pink papules (usually medium vessels) or stellate dark purple plaques (Fig. 1-23), and may be accompanied by pink, red, or purple net-like (“retiform”) hyperemia (“livedo”).
Figure 1-23 Retiform purpura with ulceration and eschar, cutaneous polyarteritis nodosa.
