Dermatologic terminology

A bruise, also known as a contusion, is a type of hematoma of tissue, the most common cause being capillaries damaged by trauma, causing localized bleeding that extravasates into the surrounding interstitial tissues. Most bruises occur close enough to the epidermis such that the bleeding causes a visible discoloration. The bruise then remains visible until the blood is either absorbed by tissues or cleared by immune system action. Bruises which do not blanch under pressure can involve capillaries at the level of skin, subcutaneous tissue, muscle, or bone.

Nevus () is a nonspecific medical term for a visible, circumscribed, chronic lesion of the skin or mucosa. The term originates from , which is Latin for "birthmark"; however, a nevus can be either congenital (present at birth) or acquired. Common terms (mole, birthmark, beauty mark, etc.) are used to describe nevi, but these terms do not distinguish specific types of nevi from one another.

thumb|Benign cyst kidney; radiological appearances mimic renal cancer. A cyst is a closed sac in the body, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble); however, the distinguishing aspect of a cyst is that the cells forming the "shell" of such a sac are distinctly abnormal (in both appearance and behaviour) when compared with all surrounding cells for that given location. A cyst may contain air, fluids, or semi-solid mat

lesion on the surface of the skin or a mucous surface, produced by the sloughing of inflammatory necrotic tissue

A rash is a change of the skin that affects its color, appearance, or texture.

thumb|Black squirrel|Melanistic black [[eastern grey squirrel (Sciurus carolinensis)]] thumb|Melanistic guinea pigs (Cavia porcellus) are rare, and are used in rituals by Andean [[curanderos.]]

A comedo (plural comedones) is a clogged hair follicle (pore) in the skin. Keratin (skin debris) combines with oil to block the follicle. A comedo can be open (blackhead) or closed by skin (whitehead) and occur with or without acne. The word comedo comes from Latin comedere 'to eat up' and was historically used to describe parasitic worms; in modern medical terminology, it is used to suggest the worm-like appearance of the expressed material.

Xerostomia, also known as dry mouth, is a subjective complaint of dryness in the mouth, which may be associated with a change in the composition of saliva, reduced salivary flow, or have no identifiable cause.

Erythema (, ) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not associated with pathology include nervous blushes.

thumb|right|Leucistic white lions owe their colouring to a recessive allele. Note the eyes and lips remain the normal colour. Studies have shown that the reduced pigment comes from a mutation in the gene for [[tyrosinase, the same as causes Type I oculocutaneous albinism in humans.]] thumb|right|alt=All-white dominant white horse with pink skin, brown eyes, and white hooves.|This white (horse)|white horse owes its coloring to a dominant allele ([[dominant white).]] thumb|A leucistic rock dove. Both the eyes and legs are still of the normal colour. Leucism () or leukism, is a wide variety of co

Purpura () is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin secondary to platelet disorders, vascular disorders, coagulation disorders, or other causes. They measure 3–10 mm, whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm.

A papule is a small, well-defined bump in the skin. It may have a rounded, pointed or flat top, and may have a dip. It can appear with a stalk, be thread-like or look warty. It can be soft or firm and its surface may be rough or smooth. Some have crusts or scales. A papule can be flesh colored, yellow, white, brown, red, blue or purplish. There may be just one or many, and they may occur irregularly in different parts of the body or appear in clusters. It does not contain fluid but may progress to a pustule or vesicle. A papule is smaller than a nodule; it can be as tiny as a pinhead and is ty

A pimple or zit is a kind of comedo that results from excess sebum and dead skin cells getting trapped in the pores of the skin. In its aggravated state, it may evolve into a pustule or papule. Pimples can be treated by acne medications, antibiotics, and anti-inflammatories prescribed by a physician, or various over the counter remedies purchased at a pharmacy.

Pallor is a pale color of the skin that can be caused by illness, emotional shock or stress, stimulant use, or anemia, and is the result of a reduced amount of oxyhaemoglobin and may also be visible as pallor of the conjunctivae of the eyes on physical examination.

An exanthem is a widespread rash eruption occurring on the outside of the body, usually presents in children, the rash is typically associated with constitutional symptoms including fever and fatigue. It is usually caused by a virus, but an exanthem can be caused by bacteria, toxins, drugs, other microorganisms, or as a result of autoimmune disease. Exanthems associated with viruses are usually not specific but some are pathognomonic for certain viruses, the rash is not caused by the virus itself but the body's reaction to the virus.

solid, non-blisterform elevated areas in or under the skin

Xeroderma is a skin condition characterized by excessively dry skin. The synonyms xerosis and xerosis cutis are sometimes used in a medical context. Colloquially, xeroderma may be referred to as dry skin or as ashiness or ashy skin when present in dark skin. Xeroderma derives .

Telangiectasias (), also known as spider veins, are small dilated blood vessels that can occur near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. These dilated blood vessels can develop anywhere on the body but are commonly seen on the face around the nose, cheeks and chin. Dilated blood vessels can also develop on the legs, although when they occur on the legs, they often have underlying venous reflux or "hidden varicose veins" (see Venous hypertension section below). When found on the legs, they are found specifically on the upper thigh, bel

Pyoderma means any skin disease that is pyogenic (has pus). These include superficial bacterial infections such as impetigo, impetigo contagiosa, ecthyma, folliculitis, Bockhart's impetigo, furuncle, carbuncle, tropical ulcer, etc. Autoimmune conditions include pyoderma gangrenosum. Pyoderma affects more than 111 million children worldwide, making it one of the three most common skin disorders in children along with scabies and tinea.

Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis, or skin), often associated with the presence of an abnormal quantity of keratin, and is usually accompanied by an increase in the granular layer. As the corneum layer normally varies greatly in thickness in different sites, some experience is needed to assess minor degrees of hyperkeratosis.

Intertrigo, commonly called "skin fold dermatitis", refers to a type of inflammatory rash (dermatitis) of the superficial skin that occurs within a person's body folds. These areas are more susceptible to irritation and subsequent infection due to factors that promote skin breakdown such as moisture, friction, and exposure to bodily secretions and excreta such as sweat, urine, or feces. Areas of the body which are more likely to be affected by intertrigo include the inframammary fold, intergluteal cleft, armpits, and spaces between the fingers or toes. Skin affected by intertrigo is more prone

congenital disorder characterized by the complete or partial absence of pigment in the skin

thumb|Polarized light dermatoscope

classification of skin color and response to UV light

Hyperpigmentation is a condition characterized by the darkening of an area of the skin or nails due to an excess production of melanin, the pigment responsible for skin color. This increase in melanin can result from a variety of factors, including sun exposure, inflammation, trauma, certain medications, or underlying medical conditions.

Desquamation, or peeling skin, is the shedding of dead cells from the outermost layer of skin.

Poliosis circumscripta, commonly referred to as a "white forelock", is a condition characterized by localized patches of white hair due to a reduction or absence of melanin in hair follicles. Although traditionally associated with the scalp, poliosis can affect any hairy area on the body, including eyebrows, eyelashes, and beards. Microscopically, poliosis is marked by the lack of melanin or melanocytes in the hair bulbs, though epidermal melanocytes typically remain unaffected unless associated with conditions like vitiligo.

Keratosis (from kerat- + -osis) is a growth of keratin on the skin or on mucous membranes stemming from keratinocytes, the prominent cell type in the epidermis. Most are not serious but actinic keratosis (also known as solar keratosis) and chronic scar keratosis, are precancerous conditions.

Acantholysis is the loss of intercellular connections, such as desmosomes, resulting in loss of cohesion between keratinocytes, seen in diseases such as pemphigus vulgaris, Grover’s disease, and Hailey-Hailey Disease. It is absent in bullous pemphigoid, making it useful for differential diagnosis. This disruption between cells causes intra-epidermal clefts, vesicles and bullae due to cells becoming rounded and no longer attached to one another.

Pityriasis commonly refers to flaking (or scaling) of the skin. The word comes from the Greek πίτυρον 'bran'.

Hypopigmentation is characterized specifically as an area of skin becoming lighter than the baseline skin color, but not completely devoid of pigment. This is not to be confused with depigmentation, which is characterized as the absence of all pigment. It is caused by melanocyte or melanin depletion, or a decrease in the amino acid tyrosine, which is used by melanocytes to make melanin. Some common genetic causes include mutations in the tyrosinase gene or OCA2 gene. As melanin pigments tend to be in the skin, eye, and hair, these are the commonly affected areas in those with hypopigmentation.

thumb|Early actinic keratosis with parakeratosis, with black arrows indicating one of multiple retained nuclei in the stratum corneum Parakeratosis is a mode of keratinization characterized by the retention of nuclei in the stratum corneum. In mucous membranes, parakeratosis is normal. In the skin, this process leads to the abnormal replacement of annular squames with nucleated cells. Parakeratosis is associated with the thinning or loss of the granular layer and is usually seen in diseases of increased cell turnover, whether inflammatory or neoplastic. Parakeratosis is seen in the plaques of

thumb|This green-striped grasshopper is not very green due to erythrism. thumb|An erythristic Welsh polecat Erythrism or erythrochroism refers to an unusual reddish pigmentation of an animal's hair, skin, feathers, or eggshells.

scale used to classify male pattern baldness

A dermatomycosis is a skin disease caused by a fungus. Most dermatomycoses are mild and resolve without treatment, but many are treated clinically with topical antifungal medicines. Oral antifungals are also an option for treatment.

Melanosis is a form of hyperpigmentation associated with increased melanin.

thumb|right|330px|Diascopy of a red dot Basal-cell carcinoma|basal cell carcinoma on the left mid back of a 74-year-old female. The red dot basal cell carcinoma on the left mid back is circled; the tumor blanches when a glass microscope slide is pressed against it. From a case series by Philip R Cohen, 2017. Diascopy is a test for blanchability performed by applying pressure with a finger or glass slide and observing color changes.

red, scaly rash of the cheeks and bridge of the nose

Lichenification is a cutaneous condition caused by consistent irritation of the skin, such as scratching or rubbing, but can also be caused by friction from clothing or chemical irritants. Lichenification can develop from scratching existing skin conditions that cause itching such as eczema or psoriasis (secondary lichenification), but also appears on previously healthy skin when repeatedly aggravated (primary lichenification). Often times, in the case of primary lichenification, skin irritation is self inflicted due to psychiatric conditions, usually obsessive-compulsive disorder or anxiety d

Papillomatosis is skin surface elevation caused by hyperplasia and enlargement of contiguous dermal papillae. These papillary projections of the epidermis form an undulating surface under microscopic examination.

Glabrousness () is the technical term for a lack of hair, down, setae, trichomes, or other such covering. A glabrous surface may be a natural characteristic of all or part of a plant or animal, or be due to loss because of a physical condition, such as alopecia universalis in humans, which causes hair to fall out or not regrow.

thumb|Marked atypia of type 2 pneumocytes is a characteristic finding in association with treatment with [[busulfan and other chemotherapeutic agents. ]] Atypia (from Greek, a + typos, without type; a condition of being irregular or nonstandard) is a histopathologic term for a structural abnormality in a cell, i.e. it is used to describe atypical cells.

cutaneous condition

tool for measuring the severity of psoriasis

right|thumb|Often called "Albinism|albino", this amelanistic [[Burmese python owes its yellow color to unaffected carotenoid pigments.]] Amelanism (also known as amelanosis) is a pigmentation abnormality characterized by the lack of pigments called melanins, commonly associated with a genetic loss of tyrosinase function. Amelanism can affect fish, amphibians, reptiles ,(including birds) and mammals including humans. The appearance of an amelanistic animal depends on the remaining non-melanin pigments. The opposite of amelanism is melanism, a higher percentage of melanin.

Atrophoderma refers to conditions involving thinning of skin.

Dyskeratosis is abnormal keratinization occurring prematurely within individual cells or groups of cells below the stratum granulosum.

medical diagnostic method

cutaneous response from firm stroking of skin

contains granules of pigments called melanin and keratin

thumb|Histopathological image of dyshidrotic dermatitis, showing focal spongiotic change in the epidermis. Spongiosis is mainly intercellular edema (abnormal accumulation of fluid) in the epidermis, and is characteristic of eczematous dermatitis, manifested clinically by intraepidermal vesicles (fluid-containing spaces), "juicy" papules, and/or lichenification. It is a severe case of eczema that affects the epidermis, dermis or subcutaneous skin tissues. The three types of spongiotic dermatitis are acute, subacute and chronic. A dermatologist can diagnose acute spongiotic dermatitis by examini

scale of female baldness