elementary lesions and diagnostic approach in dermatology


introducedon :

The skin is the body shell, it is continuous with the mucous membranes covering the natural body cavities, it is an organ which has an area of ​​about 2 m2 in an adult, which weighs just over 3 kg, and which comprises 3 million cells per cm2

Reminder histologic :

  • Skin : is a heterogeneous structure in which there are epithelial cells as well as connective cells, muscle, vascular and nervous. The skin is made, from the outside inwards, from 4 distinct zones :

Epidermis : is the top layer of the skin, it protects against external aggressions, it measures average 0.1 mm (from 0.02 mm on the face 1-5 mm thick under the soles), it is renewed every 28 days, He understands 4 different cell populations : keratinocyte, melanocytes, Langerhans cells, Merkel cells. The epidermis contains no lymphatic or blood vessels but contains many free nerve endings. The epidermis is a multi-layered Malpighian epithelium which is composed of 4 layers :

Layer basic (stratum basal) : it is the deepest layer of the epidermis, it is formed of a single layer of cuboidal or columnar cells resting on the basal membrane of the dermo-epidermal junction (keratinocyte), this layer is the germinal compartment and the seat of a high mitotic activity

melanocytes : are regularly distributed along the basal layer in varying amounts, they have a starry appearance and their cytoplasmic extensions insinuate between the keratinocytes. They are devoid of cell junction system with neighboring cells. Melanin is the pigment produced by melanocytes in cytoplasmic organelles

Layer intermediate (stratum spinosum or stratum spinosum or mucosal body Malpighian) : this is the thickest layer, it involves 3 at 10 layers of keratinocytes polyhedral shapes, who have in their cytoplasm precursors of keratin. These cells gradually flatten towards the surface but their nuclei and organelles remain intact

Layer grainy (stratum granulosum) : it involves 2 at 3 foundations of very flattened cells, whose nuclei begin to degenerate. It appears, in keratin filaments keyrings, many grains keratohyalin and keratinosomes

Layer cornea (stratum corneum) : is the outermost layer, it is composed of hexagonal cells, flattened, orderly, like scales. Nuclei and cytoplasmic organelles have completely disappeared and the cytoplasm is filled with bunches fibrillar formed from keratin filaments and grains of keratohyalin. Surface, these corneocytes are removed from very orderly : is the physiological process of desquamation

Junction dermo-epidermal : separates the epidermis from the dermis, the complexity of its structure and functional significance make a full. It appears between the basal keratinocytes and dermal papilla as a wavy line, fine, even where alternate the projections of the epidermis into the dermis called "epidermal ridges" and the projections of the dermis in the skin called "dermal papillae". The dermo-epidermal present epidermal anchoring complex on the dermis

Dermis (Latin skin) : form a well-defined barrier, which gives the skin a tear strength and an elasticity to stretch. It is a connective member consisting of connective tissue fibers and cellular elements, it consists of a ground substance, elastic fibers, collagen fiber, vessels and nerve fibers

Hypoderme : continuing the dermis to the depth, the hypodermis is loose connective tissue, richly vascularized, who, under the terms of nutrition and skin areas, contains more or less adipose tissue divided into lobules by trabeculae

  • Vascularisation from the skin : the vessels are numerous and are located only in the dermis (the skin is nourished by imbibing), arteriovenous anastomoses are many
  • Annexes from the skin :

glands sudoripares : are tiny size, located in the dermis or the subcutaneous cellular tissue, they are in the form of tubes. These are exocrine glands (which release their secretion through an excretory duct that crosses the dermis, the epidermis and is open to the outside through a sweat pore), many (2 at 3 millions), spread in abundance on the forehead, the palms, soles of the feet, the armpit areas and genitals and are intended to secrete sweat. Where distinguishes 2 types :

glands apocrines : these glands develop during puberty, sit only at the hairy areas (armpits), they are always associated with a pilosebaceous follicle

glands eccrines : these glands sit on the body but mainly at the palms and soles. The eccrine glands play a role in thermoregulation (if fever or emotional factors), in fluid and electrolyte balance and in the elimination of metabolic wastes

follicles pilosebaceous : consist of the hair follicle which are appendues sebaceous glands secrete a lipid product and arrecteurs muscle sympathetic innervation which segmental contraction (under the effect of cold, fear ...) triggers the hair recovery (goosebumps)

Structure of hair : the hair is a flexible rod that is strong and elastic, about 0,1 mm, it is installed diagonally in the scalp. At its deepest part, he joined a small bag that is called "follicle"

Growth of hair : hair growth is not continuous but cyclic, and you lose monthly from 80 at 100 hair day. On distingue 3 phases :

Phase anagen : lasts about 1000 days but can range from 2 at 6 years in men and is the hair growth phase. During the anagen, the hair growth rate is rapid, reaching about half an inch per month

Phase catagen : lasts only 3 weeks, it is the transition phase or hair regression, it precedes the resting stage. During the catagen stage, the hair growth cycle slows and then stops

Phase telogen : of a period of 5 at 6 weeks, is the resting phase where the hair does not grow but remains anchored in the follicle. Only at the end of this phase, the hair falls

nails :

Structure : is the dorsal cutaneous surface of each finger and each toe, form a very specialized Schedule. The nail has multiple functions : protection, static shot of back pressure in the pulp touch sensitivity, fine outlet, aggressive role or aesthetic

Architecture : microscopically, describes the nail 2 parties : a visible portion (body of the nail or the lamina) and a hidden part under a skin fold (racine). The lunula is the whitish part of the limbus, located near the root, it is particularly well developed at the level of the thumbs. The skin that covers the nail root is called "nail bead" and its free end (very keratinized) "Eponychium" or cuticle, while the area under the free edge of the nail is "hyponychium"

Steps diagnosis in dermatology :

  • Skin responds to stress and diseases it is subjected by the changes visible and / or palpable called "elementary lesions"
  • The identification of these lesions based on clinical examination to be completed, if necessary, some additional tests
  • Dermatological apparatus includes skin, mucous membranes and skin appendages (nails and hair), characterized by its extended, accessibility to the semiotic analysis and paraclinical gestures (biopsy e.g.) and his involvement in many general ailments (mirror of internal diseases)
  • The purpose of the review is to make a diagnosis -> treatment
  • In theory, we can contrast two different clinical approaches :

Steps analog : fast, making the diagnosis from a clinical inspection characteristic appearance, it requires having seen the lesion to recognize it and has the risk of error

Method analytic : reasoned, is slower, it corresponds to a conventional medical approach : data collection (analysis) before diagnosis (synthesis). This is the method that will be described here

  • The diagnosis in dermatology based on the interrogation, physical examination and additional investigations

Examination : clarify the history of the disease (start mode : sudden or gradual, localized or diffuse), the appearance of the initial lesion, the evolution of the lesion, the evolution of the disease, functional signs (pruritus) and general signs. It should also clarify the concept of prior drug intake (toxiderma, induced dermatoses), environmental factors (profession, habitat, sun exposure) and psychological factors

Exam dermatological : essentially based on inspection, palpation and incidentally on vitropression, curettage and friction ...

At plan morphologic :

Identification from the lesion elementary : cut, form, surface, consistency, color

Identification of the LesiaU.S formed : isolated or grouped (punctiformes, lenticulaires, nummulaires, plaques, tablecloths, universalis group or a figurative : linear, annular, arciforme, zoniforme)

Identification from the topography : ubiquitous or elective (open areas -> photo-dermatose, zones bastion -> psoriasis ≠ lichen plan…)

At plan functional :

PRuhr : symptom master, either absent or present, we must specify its intensity, the moment of occurrence (daytime, nocturne, permanent, paroxysmal, effort, repos), the exact topography

Other : burning sensation, baking, pain

Exam of the mucous and of the appendages

At plan general : examination of other organs (nodes ...), general signs

exams Additional : in many cases, analysis of skin lesions enables readily lead to a diagnosis or group of diagnosis but sometimes, paraclinical explorations are essential

Specimens microbiological superficial : they can be made by scratching, puncture, swab or smear ... in search of an infectious agent responsible for a bacterial skin disease, fungal (Direct examination and culture of dermatophytes or yeasts), parasitic (Research mites by shaving) or viral

Biopsy cutaneous : it is performed when the clinical semiological analysis is insufficient to provide a definite diagnosis, it allows histological analysis(s) the / lesion(s) elementary(s) of which a small fragment (few millimeters in diameter) is taken after local anesthesia. Two sampling techniques are possible :

Punch : is a cookie cutter having a circular cylindrical blade which provides a skin carrot, This technique is often performed in children because the response time is greatly reduced

Biopsy at bistoury : is classic, it is performed according to an incision ellipse, realizing a levy of orange, a second suture is, here, indispensable

Explorations allergy : often necessary to prove the allergic nature of a dermatosis and especially to specify the allergen in question in order to avoid it to prevent recurrence

Tests patch : are indicated during contact eczemas, in particular professionals

Tests photobiological : are indicated in dermatosis by photosensitization

main injury elementary :

  • lesions nonpalpable :

Macule : task, lesion of a few millimeters to few centimeters in diameter, visible but non-palpable. Corresponds to a simple color change :

Macule erythematous :

fading away at the vitropression : telangiectasia, erythema

Persistent at the vitropression : purpura

Macule dyschromique :

Macules pigmented : freckles (freckles)

Macules achromiques or whitish : vitiligo

▪ To erythema, is a localized or diffuse redness of the skin, fading to vitropression, on distingue :

Erythema widespread :

From type scarlatiniforme : bright red erythema, in large continuous cupboards, without intervals of healthy skin (ex : scarlatine)

From type morbilliform : red rash extended, made of small parts with healthy skin intervals (ex : measles)

From type roséoliforme : erythema due to stains, poorly demarcated with wide intervals skin healthy (ex : secondary syphilis)

erythroderma : generalized rash that affects more than 90% of the body surface (ex : erythrodermic psoriasis)

Erythema localized : ex : photosensitivity

  • lesions palpable :

contents Non-liquidien :

Papule : solid protruding wheal, palpable, non-liquid contents, whose diameter is less than 1 cm (ex : urticaria)

Nodule : protruding rise, circumscribed, measuring more than 1 cm (ex : nodular basal cell carcinoma)

Gomme : bulky dermo-hypodermic inflammatory training, Going through 4 stages : nodules -> softening -> ulceration -> healing (ex : tuberculous gum)

Vegetation : threadlike growths look, of soft, raised lesion, irregular surface, traversed by fissure furrows (cauliflower look, ex : condylomes)

Verrucosité : vegetation whose surface is covered with a coating keratotic (ex : wart)

contents liquidien :

Vesicle : lesion of a few millimeters (< 3 mm) of diameter, embossed, to clear liquid contents (ex : eczema)

Bubble : lesions measuring more than 5 mm, embossed, to clear content, disorder or haemorrhagic (ex : bubbles autoimmune bullous dermatoses (pemphigus))

Pustule : circumscribed elevation of the skin containing pus, or follicular (centered by a bristle, ex : acne) or non-follicular (ex : pustular psoriasis)

  • lesions through alteration from la surface from the skin : normal skin is dry, smooth, it is altered when it becomes rough, squameuse voire absente

Exulcération (erosion) : superficial loss of substance, affecting only the epidermis (ex : syphilitic chancre, mouth sores)

Ulceration : defect affecting the dermis, followed by scar (ex : leg ulcer)

Croute : superficial drying out of an exudate, of a secretion, skin serosity or hemorrhage

squames : stratum corneum strips detaching the skin surface, they are less adherent and off easily, they are visible or spontaneously appear after scraping with a foam edge curette. classically, on distingue :

squames scarlatiniformes : squames en grands lambeaux, reflecting a sharp horny production and intense

squames in collar : petites squames fines, adherent to the center but not on the periphery, covering an inflammatory lesion (ex : Rose Pityriasis Rosea)

squames pityriasiformes : petites squames fines, little adherent, whitish

floury, they are typical of pityriasis capitis (dandruff)

squames ichtyosiformes : grandes squames polygonales, like fish scales, separating from a very dry integument

squames psoriasiform : white scales, bright, lamellar, large and numerous (ex : psoriasis)

  • lesions through modification from the consistency from the skin : the skin becomes too much or enough soup

Atrophy : thinning of the skin, whitish lesion, pearly, Skin depressed, is finely narrowed (ex : lichen sclerosus)

Sclerosis : hardening of the skin, which becomes difficult to wrinkle erasure relief (ex : scleroderma)

Note : poikiloderma : variegated state, comprising, on the same lesion, atrophy, leucomélanodermie and telangiectasia (ex : Xeroderma Pigmentosum)

  • Some easy ways to refine the diagnosis :

Vitropression : is to apply a transparent object (glass or plastic) against the skin lesion thereby allowing the bleed to death (ex : erythema fades to vitropression)

Exam in light from Wood : is to examine in ultraviolet light skin with dark (infectious dermatoses ...)

Application from ink from China : to search for scabious burrows

Stimulation linear closed : using a soft tip, allows you to search for dermographism

Scraping at ugly d & rsquo; a curette mousse (the Brocq) : helps reveal the characteristic scaling of psoriasis

Exam at the loupe dermatological : refines inspection

dermoscopy : for examining lesions in emersion and epi-illumination, allows, after applying a drop of oil, carry out an inspection through the horny layer becomes transparent

lesions histological elementary :

The histopathological terminology is essential for effective clinicopathological confrontation

  • lesions epidermal :

Acanthose : is defined as an increase of the overall thickness of the epidermis, acanthosis can be diffuse or selectively affect the epidermal ridges, in that case, acanthosis is called "psoriasiform". If selective increase in thickness of the granular layer, we speak of "hypergranulosis", lichen planus constitutes its typical example

hyperkeratosis : is a thickening of the stratum corneum, it can only be on when there is a decrease in the thickness of the stratum spinosum and granulosum under- underlying. If keratinocytes keep their usual appearance devoid of nuclei, it is hyperkeratosis "orthokeratosic". The "parakeratosis" is defined as a persistent nuclei in corneocytes, it is mainly observed in diseases where epidermal renewal is accelerated

Acantholyse : is characterized by a loss of intercellular connection keratinocyte, the cells appeared isolated from each other and this leads to the formation of bubbles intraepidermal, as in pemphigus. This acantholyse can be observed at all levels of the epidermis

Spongiose : resulting in a gap of keratinocytes each other because of intercellular edema, the intercellular spaces are clear and expanded, giving images in "mesh"

  • alterations dermoepidermal :

papillomatosis : resulting in an exaggeration of drawing buds and inter peaks- papillary, it is therefore accompanied frequently acanthosis

  • lesions dermal :

Atrophy dermal : is characterized by a reduction in its overall thickness, depletion of collagen and hypotrophy of Annexes

Sclerosis : defines itself, on the contrary, by thickening collagen, which becomes very horizontal

fibrosis : refers to an increase of collagen fibers and dermal fibroblasts

  • lesions hypodermiques :

cytosteatonecrosis (fat necrosis) : results in the presence of adipocytes burst leading to puddles of melted fat slightly basophil

Conclusion :

The architecture of the skin is a complex that includes several cell populations and Annexes. A good physical examination can identify the elementary lesion that is the cornerstone for diagnosis. Given the accessibility of the skin, some additional tests can help our diagnostic approach. Any elementary lesion semiotic has histologic interpretation (Histological elementary lesion)