List of skin conditions


Many conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment. The skin weighs an average of four kilograms, covers an area of two square metres, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles, and hair-bearing skin. Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands form from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.
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. Nourishment is provided to these layers by diffusion from the dermis, since the epidermis is without direct blood supply. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95 percent of the epidermis. This stratified squamous epithelium is maintained by cell division within the stratum basale, in which differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where cells are continually shed from the surface. In normal skin, the rate of production equals the rate of loss; about two weeks are needed for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.
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 with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. Structural components of the dermis are collagen, elastic fibers, and ground substance. Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands. The dermis contains two vascular networks that run parallel to the skin surface—one superficial and one deep plexus—which are connected by vertical communicating vessels. 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.
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. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.
Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states. While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location, morphology, etiology, and so on. Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion, including the location, symptoms, duration, arrangement, morphology, and color. Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.

Acneiform eruptions

s are caused by changes in the pilosebaceous unit.
are a group of inherited disorders characterized by bouts of inflammatory skin lesions and periodic fevers.
Chronic blistering cutaneous conditions have a prolonged course and present with vesicles and bullae.
Conditions of the mucous membranes involve the moist linings of the eyes, nose, mouth, genitals, and anus.
Conditions of the skin appendages are those affecting the glands of the skin, hair, nails, and arrector pili muscles.
Conditions of the subcutaneous fat are those affecting the layer of adipose tissue that lies between the dermis and underlying fascia.
Cutaneous congenital anomalies are a diverse group of disorders that result from faulty morphogenesis, the biological process that forms the shape of a human body.
Connective tissue diseases are caused by a complex array of autoimmune responses that target or affect collagen or ground substance.
Abnormalities of dermal fibrous and elastic tissue are caused by problems in the regulation of collagen synthesis or degradation.
|alt=Fuzzy red lines on an abdomen
Dermal and subcutaneous growths result from reactive or neoplastic proliferation of cellular components of the dermis or subcutaneous tissue, or neoplasms invading or aberrantly present in the dermis.
is a general term for "inflammation of the skin".
is a chronic dermatitis associated with a hereditary tendency to develop allergies to food and inhalant substances.
is caused by certain substances coming in contact with the skin.
refers to a broad range of conditions that begin as spongiotic dermatitis and may progress to a lichenified stage.
|alt=Small blisters and crusting on the distal fingertips
Pustular dermatitis is an inflammation of the skin that presents with pustular lesions.
is a chronic, superficial, inflammatory disease characterized by scaling on an erythematous base.
Disturbances of human pigmentation, either loss or reduction, may be related to loss of melanocytes or the inability of melanocytes to produce melanin or transport melanosomes correctly.
Drug eruptions are adverse drug reactions that present with cutaneous manifestations.
Endocrine conditions often present with cutaneous findings as the skin interacts with the endocrine system in many ways.
Eosinophilic cutaneous conditions encompass a wide variety of diseases that are characterized histologically by the presence of eosinophils in the inflammatory infiltrate, or evidence of eosinophil degranulation.
Epidermal nevi, neoplasms, and cysts are skin lesions that develop from the epidermal layer of the skin.
s are reactive skin conditions in which there is blanchable redness.
are inherited genetic skin conditions often grouped into three categories: chromosomal, single gene, and polygenetic.
Infection-related cutaneous conditions may be caused by bacteria, fungi, yeast, viruses, or parasites.

Bacterium-related

Bacterium-related cutaneous conditions often have distinct morphologic characteristics that may be an indication of a generalized systemic process or simply an isolated superficial infection.
Mycobacterium-related cutaneous conditions are caused by Mycobacterium infections.
Mycosis-related cutaneous conditions are caused by fungi or yeasts, and may present as either a superficial or deep infection of the skin, hair, or nails.
Parasitic infestations, stings, and bites in humans are caused by several groups of organisms belonging to the following phyla: Annelida, Arthropoda, Bryozoa, Chordata, Cnidaria, Cyanobacteria, Echinodermata, Nemathelminthes, Platyhelminthes, and Protozoa.
Virus-related cutaneous conditions are caused by two main groups of viruses–DNA and RNA types–both of which are obligatory intracellular parasites.
Lichenoid eruptions are dermatoses related to the unique, common inflammatory disorder lichen planus, which affects the skin, mucous membranes, nails, and hair.
Lymphoid-related cutaneous conditions are a group of disorders characterized by collections of lymphocyte cells within the skin.
Melanocytic nevi and neoplasms are caused by either a proliferation of melanocytes, or nevus cells, a form of melanocyte that lack dendritic processes.
is a malignant proliferation of melanocytes and the most aggressive type of skin cancer.
Monocyte- and macrophage-related cutaneous conditions are characterized histologically by infiltration of the skin by monocyte or macrophage cells, often divided into several categories, including granulomatous disease, histiocytoses, and sarcoidosis.
are a group of conditions caused by dermal fibroblasts producing abnormally large amounts of mucopolysaccharides.
Neurocutaneous conditions are due organic nervous system disease or are psychiatric in etiology.
Noninfectious immunodeficiency-related cutaneous conditions are caused by T-cell or B-cell dysfunction.
Nutrition-related cutaneous conditions are caused by malnutrition due to an improper or inadequate diet.
cutaneous conditions are those that present with papules and scales caused by a thickening of the stratum corneum.
|alt=Multiple, red, well demarcated papules and plaques on the flank of an adult male
are a diverse group of hereditary and acquired keratodermas in which there is hyperkeratosis of the skin of the palms and soles.
|alt=Bottom of an adult's foot with a thickened and scaling surface
Pregnancy-related cutaneous conditions are a group of skin changes observed during pregnancy.
, commonly known as itchiness, is a sensation exclusive to the skin, and characteristic of many skin conditions.
is a common, chronic, and recurrent inflammatory disease of the skin characterized by circumscribed, erythematous, dry, scaling plaques.
|alt=Large, red, scaly plaque
constitute a spectrum of disease mediated by neutrophils, and typically associated with underlying diseases, such as inflammatory bowel disease and hematologic malignancy.
|alt=Multiple ulcerations with undermined edges on the adult back and upper, posterior arm
Recalcitrant palmoplantar eruptions are skin conditions of the palms and soles which are resistant to treatment.
Skin conditions resulting from errors in metabolism are caused by enzymatic defects that lead to an accumulation or deficiency of various cellular components, including, but not limited to, amino acids, carbohydrates, and lipids.
Skin conditions resulting from physical factors occur from a number of causes, including, but not limited to, hot and cold temperatures, friction, and moisture.
Ionizing radiation-induced cutaneous conditions result from exposure to ionizing radiation.
is a vascular reaction of the skin characterized by the appearance of wheals, which are firm, elevated swelling of the skin. Angioedema, which can occur alone or with
urticaria, is characterized by a well-defined, edematous swelling that involves subcutaneous tissues, abdominal organs, or upper airway.
|alt=Raised, edematous, red skin lesions on the abdomen
Vascular-related cutaneous conditions result from dysfunction of the blood or blood vessels in the dermis, or lymphatics in the subcutaneous tissues.