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introduction to dermatology for medical students
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Dr Chaitanya Vemuri
Primary Skin LesionsMaculePatchPapuleNoduleTumorPlaqueVesiclePustuleBullaeWhealTelangiectasiaAbscessPetechiae, purpura & ecchymosis
MaculeA flat, colored
lesion, <2cm in diameter, not raised above the surface of surrounding skin
Freckle – prototype of pigmented macule
Macule
patchA large(>2cm)flat
lesion with a color different from surrounding skin
Differs from macule only in size
PapuleA small, solid lesion,
<0.5 cm in diameter, raised above the surface of surrounding skin & hence palpable
Eg: white head in acne
Papule
NoduleA large ( 0.5 – 5.0
cm ), firm lesion raised above the surface of surrounding skin.
Differs from papule only in size
TumorA solid,raised
growth >5cm in diameter
PlaqueA large >1cm, flat
topped raised lesion, edges may either be distinct ( in psoriasis ) or gradually blend with surrounding skin ( in eczematous dermatitis )
VesicleA small, fluid filled
lesion, <0.5 cm in diameter, raised above the plane of surrounding skin. Fluid is often visible and the lesion are translucent
Vesicles in Allergic Contact Dermatitis
PustuleA vesicle filled with
leukocytes The presence of
pustule does not necessarily signify the the existance of infection
AbscessA localised
collection of pus in a cavity, more than 1 cm in diameter
bullaA fluid filled, raised,
often a translucent lesion >0.5cm in diameter
WhealA raised,
erythematous, edematous, papule / plaque, usually representing short-lived vasodilatation and vasopermeability
Eg: utricaria
telangiectasiaA dilated superficial
blood vessel.
Petechiae, purpura & ecchymosisPetechiae – pinhead-sized macules of
extravascular blood in the dermis.Petechiae are flat.The larger ones are referred to as purpuraIf bleeding involves deeper structures then it
is an ecchymosis
BurrowA linear or cuvillinear papule, caused by
burrowing scabies mite
ComedonesA plug of keratin and sebum wedged in
dilated pilosebaceous orifice.
Secondary Skin LesionsScale CrustExcoriationErosionFissureSinusScarAtrophyStriaeLichenification
ScaleA flake arising from
stratum corneum d/t excessive accumulation.
Eg: psoriasis
CrustDried exudate of
body fluids (blood / serous fluid)
Which might be either yellow ( serous crust )
red ( h’agic crust )
UlcerAn area of skin from
which the whole of epidermis & atleast the upper part of dermis has been lost
ExcoriationLinear, angular
erosions that may be covered by crust and are caused by scratching.
Erosion Area of skin
denuded by complete or partial loss of epidermis.
No associated loss of dermis
Fissure A slit- shaped deep
ulcerEg: irritant
dermatitis of hands
Sinus A cavity or channel
that permits the escape of pus or fluid
Scar A change in the skin
secondary to trauma or inflammation
Sites may be erythematous, hypopigmented or hyperpigmented depending upon their age /character.
Scar
Atrophy A accquired loss of
substance .In skin, this may
appear as a depression with intact epidermis ( loss of dermal /subdermal tissues )
Or appear as sites of shiny, delicate, wrinkled lesions ( epidermal atrophy )
Striae A streak like, linear ,
atrophic, pink, purple or white lesion d/t changes in connective tissue
Eg: cushings syndrome, pregnancy induced
Lichenification A distinctive
thickening of skin that is characterized by accenuated skin-fold markings.