Cutaneous condition

Cutaneous condition
Classification and external resources
Specialty Dermatology

A cutaneous condition is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, hair, nails, and related muscle and glands.[1] The major function of this system is as a barrier against the external environment.[2]

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).[3][4] While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described.[5] Classification of these conditions often presents many nosological challenges, since underlying causes and pathogenetics are often not known.[6][7] 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.[8][9]

Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow).[10] The diagnosis of many conditions often also requires a skin biopsy which yields histologic information[11][12] that can be correlated with the clinical presentation and any laboratory data.[13][14] The introduction of cutaneous ultrasound has allowed the detection of cutaneous tumors, inflammatory processes, nail disorders and hair diseases.[15]

Layer of skin involved

The skin weighs an average of 4 kg (8.8 lb), covers an area of 2 m2 (22 sq ft), and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue.[1] The two main types of human skin are glabrous skin, the nonhairy skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin.[16] Within the latter type, hairs in structures called pilosebaceous units have a hair follicle, sebaceous gland, and associated arrector pili muscle.[17] 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.[18][19][20]

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.[21] Nourishment is provided to these layers via diffusion from the dermis, since the epidermis is without direct blood supply.[22] 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.[16] 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.[16] 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.[23]

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.[24] The superficial papillary dermis interdigitates with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone.[24] Structural components of the dermis are collagen, elastic fibers, and ground substance also called extra fibrillar matrix.[24] Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands.[21] 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.[21][25] 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.[26][27]

Subcutaneous tissue

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia.[5] 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.[16] The main cellular component of this tissue is the adipocyte, or fat cell.[5] The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance.[21] Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.[5]

Diseases of the skin

Skin diseases deaths per million persons in 2012
  0-2
  3-4
  5-8
  9-13
  14-17
  18-21
  22-27
  28-34
  35-47
  48-106

Diseases of the skin include skin infections and skin neoplasms (including skin cancer).[28]

History

In 1572, Geronimo Mercuriali of Forlì, Italy, completed De morbis cutaneis (translated "On the diseases of the skin"). It is considered the first scientific work dedicated to dermatology.

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.[29] Most of these conditions present with cutaneous surface changes termed "lesions," which have more or less distinct characteristics.[30] Often proper examination will lead the physician to obtain appropriate historical information and/or laboratory tests that are able to confirm the diagnosis.[29] Upon examination, the important clinical observations are the (1) morphology, (2) configuration, and (3) distribution of the lesion(s).[29] With regard to morphology, the initial lesion that characterizes a condition is known as the "primary lesion," and identification of such a lesions is the most important aspect of the cutaneous examination.[30] Over time, these primary lesions may continue to develop or be modified by regression or trauma, producing "secondary lesions."[1] However, with that being stated, the lack of standardization of basic dermatologic terminology has been one of the principal barriers to successful communication among physicians in describing cutaneous findings.[21] Nevertheless, there are some commonly accepted terms used to describe the macroscopic morphology, configuration, and distribution of skin lesions, which are listed below.[30]

Lesions

Primary lesions

Chigger bites on human skin showing characteristic welts
Macule and patch
Papule and plaque
Nodules
Vesicles and bulla
Fissures, erosions and ulcers
A pustule on the cheek

Secondary lesions

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: wart-like

Distribution

"Distribution" refers to how lesions are localized. They may be confined to a single area (a patch) or may exist in several places. Some distributions correlate with the means by which a given area becomes affected. For example, contact dermatitis correlates with locations where 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

Histopathology

References

  1. 1 2 3 4 5 6 Miller, Jeffrey H.; Marks, James G. (2006). Lookingbill and Marks' Principles of Dermatology. Saunders. ISBN 1-4160-3185-5.
  2. ↑ Lippens, S; Hoste, E; Vandenabeele, P; Agostinis, P; Declercq, W (April 2009). "Cell death in the skin". Apoptosis. 14 (4): 549–69. PMID 19221876. doi:10.1007/s10495-009-0324-z.
  3. ↑ King, L.S. (1954). "What Is Disease?". Philosophy of Science. 21 (3): 193–203. doi:10.1086/287343.
  4. ↑ Bluefarb, Samuel M. (1984). Dermatology. Upjohn Co. ISBN 0-89501-004-6.
  5. 1 2 3 4 Lynch, Peter J. (1994). Dermatology. Williams & Wilkins. ISBN 0-683-05252-7.
  6. ↑ Tilles G, Wallach D (1989). "[The history of nosology in dermatology]". Ann Dermatol Venereol (in French). 116 (1): 9–26. PMID 2653160.
  7. ↑ Lambert WC, Everett MA (October 1981). "The nosology of parapsoriasis". J. Am. Acad. Dermatol. 5 (4): 373–95. PMID 7026622. doi:10.1016/S0190-9622(81)70100-2.
  8. ↑ Jackson R (1977). "Historical outline of attempts to classify skin diseases". Can Med Assoc J. 116 (10): 1165–8. PMC 1879511 Freely accessible. PMID 324589.
  9. ↑ Copeman PW (February 1995). "The creation of global dermatology". J R Soc Med. 88 (2): 78–84. PMC 1295100 Freely accessible. PMID 7769599.
  10. ↑ Fitzpatrick, Thomas B.; Klauss Wolff; Wolff, Klaus Dieter; Johnson, Richard R.; Suurmond, Dick; Richard Suurmond (2005). Fitzpatrick's color atlas and synopsis of clinical dermatology. McGraw-Hill Medical Pub. Division. ISBN 0-07-144019-4.
  11. ↑ Werner B (August 2009). "[Skin biopsy and its histopathologic analysis: Why? What for? How? Part I]". An Bras Dermatol (in Portuguese). 84 (4): 391–5. PMID 19851671.
  12. ↑ Werner B (October 2009). "[Skin biopsy with histopathologic analysis: why? what for? how? part II]". An Bras Dermatol (in Portuguese). 84 (5): 507–13. PMID 20098854. doi:10.1590/S0365-05962009000500010.
  13. ↑ Xiaowei Xu; Elder, David A.; Rosalie Elenitsas; Johnson, Bernett L.; Murphy, George E. (2008). Lever's Histopathology of the Skin. Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-7363-6.
  14. ↑ Weedon's Skin Pathology, 2-Volume Set: Expert Consult – Online and Print. Edinburgh: Churchill Livingstone. 2009. ISBN 0-7020-3941-1.
  15. ↑ Fernando Alfageme, Cerezo E, Roustan G. "Real-Time Elastography in Inflammatory Skin Diseases: A Primer Ultrasound" in Medicine & Biology, Volume 41, Issue 4, Supplement, April 2015, Pages S82-S83
  16. 1 2 3 4 Burns, Tony; et al. (2006) Rook's Textbook of Dermatology CD-ROM. Wiley-Blackwell. ISBN 1-4051-3130-6.
  17. ↑ Paus R, Cotsarelis G (1999). "The biology of hair follicles". N Engl J Med. 341 (7): 491–7. PMID 10441606. doi:10.1056/NEJM199908123410706.
  18. ↑ Goldsmith, Lowell A. (1983). Biochemistry and physiology of the skin. Oxford University Press. ISBN 0-19-261253-0.
  19. ↑ Fuchs E (February 2007). "Scratching the surface of skin development". Nature. 445 (7130): 834–42. PMC 2405926 Freely accessible. PMID 17314969. doi:10.1038/nature05659.
  20. ↑ Fuchs E, Horsley V (April 2008). "More than one way to skin .". Genes Dev. 22 (8): 976–85. PMC 2732395 Freely accessible. PMID 18413712. doi:10.1101/gad.1645908.
  21. 1 2 3 4 5 6 Wolff, Klaus Dieter; et al. (2008). Fitzpatrick's Dermatology in General Medicine. McGraw-Hill Medical. ISBN 0-07-146690-8.
  22. ↑ "Skin Anatomy". Medscape. Retrieved 3 June 2013.
  23. ↑ Bolognia, Jean L.; et al. (2007). Dermatology. St. Louis: Mosby. ISBN 1-4160-2999-0.
  24. 1 2 3 Rapini, Ronald P. (2005). Practical dermatopathology. Elsevier Mosby. ISBN 0-323-01198-5.
  25. ↑ Grant-Kels, JM (2007). Color Atlas of Dermatopathology (Dermatology: Clinical & Basic Science). Informa Healthcare. p. 163. ISBN 0-8493-3794-1.
  26. ↑ Ryan, T (1991). "Cutaneous Circulation". In Goldsmith, Lowell A. Physiology, biochemistry, and molecular biology of the skin (2nd ed.). New York: Oxford University Press. p. 1019. ISBN 0-19-505612-4.
  27. ↑ Swerlick, RA; Lawley, TJ (January 1993). "Role of microvascular endothelial cells in inflammation". J. Invest. Dermatol. 100 (1): 111S–115S. PMID 8423379. doi:10.1038/jid.1993.33.
  28. ↑ "ecognizing Neoplastic Skin Lesions: A Photo Guide". American Family Physician. Retrieved 3 June 2013.
  29. 1 2 3 4 5 6 7 8 9 10 11 12 13 Callen, Jeffrey (2000). Color atlas of dermatology. Philadelphia: W.B. Saunders. ISBN 0-7216-8256-1.
  30. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 James, William D.; et al. (2006). Andrews' Diseases of the Skin: Clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
  31. 1 2 3 4 5 6 7 8 Fitzpatrick, Thomas B.; Klauss Wolff; Wolff, Klaus Dieter; Johnson, Richard R.; Suurmond, Dick; Richard Suurmond (2005). Fitzpatrick's color atlas and synopsis of clinical dermatology. New York: McGraw-Hill Medical Pub. Division. ISBN 0-07-144019-4.
  32. 1 2 Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
  33. 1 2 Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. ISBN 0-7216-0187-1.
  34. ↑ "Description of Skin Lesions". The Merk Manual. Retrieved 3 June 2013.
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