A skin condition, also known as a cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this system is to act as a barrier against the external environment.

Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), cause (skin conditions resulting from physical factors), and so on.

Clinically, the diagnosis of any particular skin condition begins by gathering pertinent information of the presenting skin lesion(s), including: location (e.g. arms, head, legs); symptoms (pruritus, pain); duration (acute or chronic); arrangement (solitary, generalized, annular, linear); morphology (macules, papules, vesicles); and color (red, yellow, etc.). Some diagnoses may also require a skin biopsy, which yields histologic information that can be correlated with the clinical presentation and any laboratory data. The introduction of cutaneous ultrasound has allowed the detection of cutaneous tumors, inflammatory processes, and skin diseases.

Layer of skin involved

The skin weighs an average of , covers an area of about , and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. Within the latter type, hairs in structures called pilosebaceous units have a hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands are from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.

Epidermis

The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95% of the epidermis.

Dermis

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. The superficial papillary dermis interdigitates with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. The function of blood vessels within the dermis is fourfold: to supply nutrition, to regulate temperature, to modulate inflammation, and to participate in wound healing.

Subcutaneous tissue

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia. This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus.

History

In 1572, Geronimo Mercuriali of Forlì, Italy, completed ('On the diseases of the skin'). It is considered the first scientific work dedicated to dermatology. <!-- This text needs no citation as it is a reference unto itself. -->

Diagnoses

The physical examination of the skin and its appendages, as well as the mucous membranes, forms the cornerstone of an accurate diagnosis of cutaneous conditions. Most of these conditions present with cutaneous surface changes termed "lesions," which have more or less distinct characteristics. Nevertheless, there are some commonly accepted terms used to describe the macroscopic morphology, configuration, and distribution of skin lesions, which are listed below.

Lesions

Primary lesions

  • Macule: A macule is a change in surface color, without elevation or depression, so nonpalpable, well or ill-defined, a circumscribed, epidermal elevation generally considered less than either 5
  • Cyst: A cyst is an epithelial-lined cavity. a lesion that is moist, circumscribed, and usually depressed.
  • Excoriation: A punctate or linear abrasion produced by mechanical means (often scratching), usually involving only the epidermis, but commonly reaching the papillary dermis.
  • Phyma: A tubercle on any external part of the body, such as in phymatous rosacea

Configuration

"Configuration" refers to how lesions are locally grouped ("organized"), which contrasts with how they are distributed (see next section).

  • Agminate: in clusters
  • Annular or circinate: ring-shaped
  • Arciform or arcuate: arc-shaped
  • Digitate: with finger-like projections
  • Discoid or nummular: round or disc-shaped
  • Figurate: with a particular shape
  • Guttate: resembling drops
  • Gyrate: coiled or spiral-shaped
  • Herpetiform: resembling herpes
  • Linear
  • Mammillated: with rounded, breast-like projections
  • Reticular or reticulated: resembling a net
  • Serpiginous: with a wavy border
  • Stellate: star-shaped
  • Targetoid: resembling a bullseye
  • Verrucous or Verruciform: wart-like

Distribution

"Distribution" refers to how lesions are localized. They may be confined to a single area (a patch) or may be in several places. Some distributions correlate with the means by which a given area becomes affected. For example, contact dermatitis correlates with locations where an allergen has elicited an allergic immune response. Varicella zoster virus is known to recur (after its initial presentation as chicken pox) as herpes zoster ("shingles"). Chicken pox appears nearly everywhere on the body, but herpes zoster tends to follow one or two dermatomes; for example, the eruptions may appear along the bra line, on either or both sides of the patient.

  • Generalized
  • Symmetric: one side mirrors the other
  • Flexural: on the front of the fingers
  • Extensor: on the back of the fingers
  • Intertriginous: in an area where two skin areas may touch or rub together
  • Morbilliform: resembling measles
  • Palmoplantar: on the palm of the hand or bottom of the foot
  • Periorificial: around an orifice such as the mouth
  • Periungual/subungual: around or under a fingernail or toenail
  • Blaschkoid: following the path of Blaschko's lines in the skin
  • Photodistributed: in places where sunlight reaches
  • Zosteriform or dermatomal: associated with a particular nerve
  • Collarette
  • Comedo
  • Confluent
  • Eczema (a type of dermatitis)
  • Evanescent (lasting less than 24 hours)
  • Granuloma
  • Livedo
  • Purpura
  • Erythema (redness)
  • Horn (a cell type)
  • Poikiloderma

Histopathology

  • Hyperkeratosis
  • Parakeratosis
  • Hypergranulosis
  • Acanthosis
  • Papillomatosis
  • Dyskeratosis
  • Acantholysis
  • Spongiosis
  • Hydropic swelling
  • Exocytosis
  • Vacuolization
  • Erosion
  • Ulceration
  • Lentiginous

See also

  • Wound, an injury which damages the epidermis.

References