Diseases of skin.... more

ELEMENTARY LESIONS AND INFECTIOUS

DISEASES OF THE SKIN

www.freelivedoctor.com

Learning ObjectivesDescribe the macroscopic and microscopic changes in frequent lesions of the skin.Define the most frequent forms of infectious skin disease and their pathogenic organisms.


REMEMBERING FEATURES OF

NORMAL SKIN



1. EPIDERMISIs subdivided into 4 layers:

Horny layer (stratum corneum)Granular layer (stratum granulosum) Malpighian layer (prickle-cell layer) Basal layer

There is an extra layer found only in palms/soleslucid layer


...(Continues) Keratinocytes are cells that mature from the basal layer to stratum corneum and their function is related to form a barrier, to secrete PGs, leukotrienes, Ils and induction of Vitamin D by UV rays. Melanocytes (3%) are dendritic cells derived from the neural crest and located into the basal layer, that produce melanin (endogenous screen against UV rays in sunlight).Langerhans cells (4%) can recognize and process Ags and communicate to lymphoid cells.


A, The skin is composed of an epidermal layer (e) from which specialized adnexa (hair follicles, h; sweat glands, g; and sebaceous glands, s) descend into the underlying dermis (d). B, This projection of the epidermal layer (e) and underlying superficial dermis demonstrates the progressive upward maturation of basal cells (b) into cornified squamous epithelial cells of the stratum corneum (sc). Melanin-containing dendritic melanocytes (m) (and rare Merkel cells containing neurosecretory granules) and midepidermal dendritic Langerhans cells (lc) are also present. The underlying dermis contains small vessels (v), fibroblasts (f), perivascular mast cells (mc), and dendrocytes (dc), potentially important in dermal immunity and repair.www.freelivedoctor.com

...(Continues) Merkel cells (<1%) are located also into the basal layer of skin/mucous membranes and function as tactile mechanoreceptor.The basal layer is responsible for epidermal-dermal adherence and probably is a macromolecular filter. It is also a major site for Igs localization.


2. DERMISPapillary dermis is immediately beneath the epidermis and is formed by collagen fibers. It reacts conjointly with epidermis and superficial capillary-venular bed. Reticular dermis contains most of dermal collagen

3. EPIDERMAL ADNEXA. Includes modified keratinized structures (nails, hair) and sebaceous, eccrine and apocrine glands (axilla, ano-genital areas, nipple and areola)

4. BLOOD VESSELS, NERVES, LYMPHATICS MUSCLES, CELLS (mast cells)


SKIN PATHOLOGY

DEFINITIONS OF MACROSCOPIC AND

MICROSCOPIC TERMS


SKIN PATHOLOGY

MACROSCOPIC TERMS


SKIN PATHOLOGYRESPONSES OF THE SKIN TO INJURY

Clinical lesions – Macroscopic terms

MaculePatchPapuleNodulePlaqueVesicleBulla

BlisterPustuleWhealScaleLichenificationExcoriationOnycholysis


SKIN PATHOLOGYMACROSCOPIC TERMS

MACULEA circumscribed lesion of up to 5 mm in diameter, characterized by flatness and usually distinguished from surrounding skin by its coloration.

PATCH A circumscribed lesion of more than 5 mm in diameter, characterized by flatness and usually distinguished from surrounding skin by its coloration.


Patch


Macules and patches



PAPULEElevated dome-shaped or flat-topped lesion 5 mm or less across.

PLAQUEElevated flat-topped lesion usually greater than 5 mm across (may be caused by coalescent papules).


Plaque




NODULEElevated lesion with spherical contour greater than 5 mm across.




VESICLEFluid-filled raised lesion 5 mm or less across.





BULLAFluid-filled lesion greater than 5 mm across.





BLISTERCommon term used for vesicle or bulla.



PUSTULEDiscrete, pus-filled, raised lesion.





WHEALItchy, transient, elevated lesion with variable blanching and erythema formed as the result of dermal edema.



SCAR Is a hard plaque of dense fibrotic tissue covered by a thin epidermis. A mark of injury from any sort of process.

ATROPHY Usually refers to thinning of the epidermiseasily wrinkled and/or shiny surface. It may also apply to dermal and/or subcutaneous tissue, with or without changes in epidermis.




ULCERLoss of skin tissue or substance from the surface downward, leaving an uncovered or denuded wound that is slow to heal.

EROSION A superficial denudation of the skin, usually implying loss of epidermis.




FISSUREIs a vertical splitting/separation of the skin

CRUSTDried surface of fluid, often serous (inspissated serum) in nature, with or without tissue debris (same as “scab”)

EXCORIATION A scratch mark, often with denudation of the skin to form a small ulcer



SCALE A thin flake of epithelium (mostly of corneum layer) which is separated from the underlying intact skin.

LICHENIFICATIONA thickening of the skin and an increase of skin markings, usually seen w/chronic coalescence of papular lesions (atopic eczema).

ONYCHOLYSISSeparation of nail plate from nail bed.


SKIN PATHOLOGY

MICROSCOPIC TERMS


SKIN PATHOLOGYRESPONSES OF THE SKIN TO INJURY

MICROSCOPIC TERMS

HyperkeratosisParakeratosisHypergranulosi

sAcanthosisPapillomatosisDyskeratosisAcantholysis

SpongiosisHydropic swelling

(ballooning)ExocytosisErosionUlcerationVacuolizationLentiginous


SKIN PATHOLOGYMICROSCOPIC TERMS

HYPERKERATOSIS: Thickening of the stratum corneum, often associated with a qualitiative abnormality of the keratin.

PARAKERATOSIS: Modes of keratinization characterized by the retention of the nuclei in the stratum corneum. On mucous membranes, parakeratosis is normal.


Hyperkeratosis


Parakeratosis



HYPERGRANULOSIS: Hyperplasia of the statum granulosum, often due to intense rubbing

ACANTHOSIS: Diffuse epidermal hyperplasia

PAPILLOMATOSIS:Surface elevation caused by hyperplasia and enlargement of contiguous dermal papillae.


Acanthosis



DYSKERATOSIS: Abnormal keratinization occurring prematurely within individual cells or groups of cells below the stratum granulosum.

ACANTHOLYSIS: Loss of intercellular connections resulting in loss of cohesion between keratinocytes.

SPONGIOSIS:Intercellular edema of the epidermis.


Acantholysis


Spongiosis



HYDROPIC SWELLING (BALLOONING)Intracellular edema of keratinocytes, often seen in viral infections.

EXOCYTOSIS: Infiltration of the epidermis by inflammatory or circulating blood cells.


Hydropic swelling (ballooning)



VACUOLIZATION: Formation of vacuoles within or adjacent to cells; often refers to basal cell-basement membrane zone area.

LENTIGINOUS:Referring to a linear pattern of melanocyte proliferation within the epidermal basal cell layer. Lentiginous melanocytic hyperplasia can occur as a reactive change or as part of a neoplasm of melanocytes.


BONUS MATERIAL


SKIN PATHOLOGYBonus Material

SKIN RESPONSE IN SYSTEMIC DISEASES.

HYPERPIGMENTATION -Addison´s disease -Hemochromatosis -Heavy metal poisoning (As,Ag) -Chronic renal failure -Chronic liver disease





SKIN RESPONSE IN SYSTEMIC DISEASESHYPOPIGMENTATION -Albinism

-Chediak-Higashi syndrome -Hypopituitarism



SKIN PATHOLOGY – Bonus Material

SKIN RESPONSE IN SYSTEMIC...DARK SPOTS -Peutz-Jegher´s syndrome -Albright´s syndrome -NeurofibromatosisORANGE-YELLOW PIGMENT

-Jaundice -Hypervitaminosis A, etc.PRURITUS

-Chronic renal failure -Obstructive jaundice -Hodgkin’s disease





SKIN RESPONSE IN SYSTEMIC...HEMORRHAGIC PETECHIAE -Bacterial endocarditis -Scurvy -Thrombocytopenic purpura -Septicemia -VasculitisBRUISES -Amyloidosis -Leukemia -Bacteremia -Scurvy -Cushing´s syndrome




SKIN RESPONSE IN SYSTEMIC...TELANGIECTASIA -Chronic liver failure -Osler-Weber-Rendu syndromeHIRSUTISM -Cushing’s syndrome -Increased levels of androgensHAIR LOSS

-Hypothyroidism -SLE



SKIN RESPONSE IN SYSTEMIC...HYPERKERATOSIS -Hypervitaminosis A -ScurvyACANTHOSIS NIGRICANS -Mostly abdominal carcinomas (stomach) -Also: some lung and breast carcinomasDERMATITIS -Hypervitaminosis A -Parkinson’s diease -Pellagra




END OF BONUS MATERIAL


SKIN PATHOLOGY

INFECTIOUS DISEASES AND INFESTATION


INFECTION AND INFESTATION

Verrucae (warts)Common lesions of children and adolescents, may be encountered at any age.

Caused by human papillomaviruses.

Generally self-limited, regressing spontaneously.

Verruca vulgarisVerruca planaVerruca plantarisVerruca palmarisCondyloma acuminatum (venereal wart)


… (Continues)…(Continues)

Pathogenesis:Anogenital warts are caused predominantly by HPV types 6 and 11 (HPV type 16 shows some degree of dysplasia, associated with in situ squamous cell carcinoma of the genitalia).HPV types 5 and 8 have been detected also.



…(Continues)Molluscum Contagiosum

Is a common self-limited viral disease of the skin caused by a poxvirus (largest pathogenic poxvirus in humans).Clinically, multiple lesions may occur on the skin and mucous membranes (trunk and anogenital areas).


SKIN PATHOLOGYVIRUSES

Herpes simplex I (oral blisters) and herpes simplex II (genital blisters). Varicella (blisters on trunkperiphery)



…(Continues)Impetigo

Common superficial bacterial infection of the skin. Pathogenesis:

Beta-hemolytic streptococci and Staphylococcus aureus (most of the cases nowadays).


…(Continues)Superficial fungal infections

Caused primarily by dermatophytes. Tinea capitisTinea barbaeTinea corporisTinea crurisTinea pedis (athlete’s foot)

Spread to or primary infection of the nails is referred to as onychomycosis.




…(Continues)…(Continues)

Tinea versicolor (Malassezia furfur), a yeast.


…(Continues)Arthropod bites, stings, and infestations

Arachnida (spiders, scorpions, ticks, and mites)Insecta (lice, bedbugs, bees, wasps, fleas, flies, and mosquitoes)Chilopoda (centipedes).



Arthropods can produce lesions:1. By direct irritant effects of insesct parts or secretions.2. By immediate or delayed hypersensitivity responses (including an anaphylactic reaction)3. By specific effects of venoms (e.g. black widow spider venom produces severe cramps and excruciating pain, the brown recluse spider venom contains potent enzymes that produce tissue necrosis)4. By serving as vectors for secondary invaders, such as viruses, bacteria, rickettsiae, and parasites.



Ixodes dammini, a tick vector for the spirochete that causes Lyme disease.Pediculosis, caused by the head louse, crab louse, and body louse.Scabies, caused by the mite Sarcoptes scabei.


Documents

Diseases of skin.... more