Page 24 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 1-9 Integumentary System

MORPHOLOGY: LICHENIFICATION, PLAQUES, AND FISSURES

MORPHOLOGY Urticaria (hives).
Evanescent pink-
red pruritic
The first lesson a student of dermatology must learn is plaques
how to properly describe skin diseases. Skin morphol-
ogy has been well defined over the years and is the basis
for all discussions about skin disorders. One must be
adept at describing skin lesions before it is possible to
develop a differential diagnosis. For example, once it
has been determined that a rash is in the morphological
category of macule, all rashes in the blistering and
nodular categories can easily be excluded from the dif-
ferential diagnosis. To get a firm grasp of dermatology, Lichen simplex
one must have an excellent foundation in description chronicus.
and morphology. The most common descriptors used Lichenified
in the dermatology lexicon are discussed here. excoriated
plaque on
Skin lesions and rashes can be described as primary
or secondary lesions. The primary category includes the ankle,
showing
macules, papules, comedones, patches, plaques, accentuation
nodules, tumors, hives, vesicles, bullae, and pustules. of the skin
The secondary lesions are best described as scales, lines
crusts, erosions, excoriations, ulcerations, fissures,
scars, lichenification, and burrows.
Many adjectives are used in conjunction with primary
and secondary descriptive terms to better characterize
the lesion and to help determine a differential diagnosis
and, ultimately, a diagnosis for the patient. Color is of
utmost importance and is universally used in the
description of skin lesions. For example, a good descrip-
tion of melanoma would include color, size, regularity,
and the primary morphology, such as “a dark black,
irregularly shaped macule with a central nodule.”
Other descriptive terms often used in dermatology
deal with the configuration of the lesion, such as a linear
or an annular configuration. Words such as arcuate,
polycyclical, nummular, and agminated are also com-
monly used. Some skin rashes tend to follow specific
types of skin lines, most commonly Langer’s lines (skin
tension lines) and Blaschko’s lines (embryological cleav-
age lines).
The distribution of skin lesions is also important,
because some skin diseases have a propensity to
occur in specific areas of the body. A classic example
is acne, which typically affects the face, upper back,
and chest. It would be inappropriate to consider acne
in the differential diagnosis of a rash on the hands
and feet.
Starting with the primary skin lesions, a macule is
most often thought of as a well-circumscribed, flat area Postauricular fissures.
on the skin with a distinct color change. The macule Fissures are linear thin erosions or ulcers
may have an irregular or a regular border. Macules are along skin lines.
not raised and are essentially nonpalpable. An example
of a macule is vitiligo.
A papule is a well-circumscribed, small (<5 mm in
diameter) elevation in the skin of variable color. A
papule is solid and should not be confused with a
vesicle. Papules may be described as flat-topped or
umbilicated, and their consistency may be characterized
as soft or firm. An example of an umbilicated papule is produced when the follicular epithelium sticks together A plaque is a well-defined lesion that has a plateau-
molluscum contagiosum. and seals the follicular orifice. like elevation and is typically larger than 5 mm in diam-
Comedones are seen in acne and in a few less common The word patch is sometimes used to describe a large eter. The term plaque can also be used to describe a
conditions. Essentially, they come in two forms, open macule. A more precise definition of a patch is an area confluence of papules. An example of a plaque is a lesion
and closed. Open comedones are also known as black- of the skin that is not elevated but has surface change of psoriasis.
heads. Each comedo represents a dilated follicular such as scale or crust. An example of a patch is tinea cor- A nodule is defined as a space-occupying lesion in the
infundibulum with a buildup of oxidized keratin. Closed poris. Depending on the source or reference review, the dermis or subcutaneous tissue. Its breadth is typically
comedones are seen as tiny white papules, which are term patch can include either of these two definitions. larger than its height. Surface changes may or may not

10 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS