Download Introduction to dermatology

INTRODUCTION TO
DERMATOLOGY
DEFINITION
 What is dermatology :
 It is the science that deal’s with the skin and study it’s diseases and
conditions
 Dermatology is defined in The New Oxford Dictionary of English as ‘The
branch of medicine concerned with the diagnosis and treatment of skin
disorders’
 Why we study the skin ?
 Because the skin the largest organ in the body and it serve many function
to human being
FUNCTIONS OF SKIN
1. Protection : Chemicals, particles, Ultraviolet radiation
,Antigens haptens , Microbes
2. Preservation of a balanced internal environment
3. Prevention of loss of water, electrolytes and macromolecules
4. Lubrication and waterproofing
5. Shock absorption : strong, yet elastic and compliant covering.
6. Sensation
7. Calorie reserve
8. Vitamin D synthesis
9. Temperature regulation
10. Psychosocial, sexual : hair, nail,..
SKIN DISEASE IMPACT
 The skin diseases impact on the human being is illustrated by the 5 D
SKIN COMPONENT
 The skin is composed from three main layers with appendages
 The main skin layers are :
 Epidermis
 Dermis
 Subcuataneous fat tissue
 The main skin appendages
 Hair
 Nails
 Sweat gland and sebaceous glands
EPIDERMIS
 Stratified sqaumous epitheium ( Keratinocytes).
 Keratinocytes:85- 95% of Epidermal cells.
 4- cell layers: Basal layer , spinous (Prickle ) layer ,Granular layer , horny
layer ( stratum corneum )
 Desmosomes: the major adhesion structure between KC. If damaged will
lead to Acantholysis (separation of keratinocytes) .
 Hemi-desmosomes : connect basal keratinocytes to the underlying
basement membrane .
EPIDERMIS-CELLS OTHER THAN KC
 Melanocytes :melanogenesis ( melanin synthesis ) , dendritic .
 Langerhans’ cells: Bone marrow - derived, APC (antigen presenting cells )
and immune surveillance, Dendritic .
 Merkel cells: basal layer, transducers for fine touch, non- Dendritic .
DERMIS
 Components: Ground Substance, Fibres (most imp collagen ), Cells and other
structures.
 Makes about 15-20% of human body weight
 thickness: 1mm eyelids , 5mm back
 Interdigitates with Epidermis via dermal papilla
APPROACH TO PATIENTS WITH
DERMATOLOGICAL DISEASE
 History
 Examination
 Dermatological investigations
 Other investigations
HISTORY
 Hx of skin lesions/rashes (dermatological hx ):
 When did it start (duration .. Acute vx chronic )
 Where did it start (site)
 How did it spread ( for ex : trunk to limbs, limbs to trunk…)
 Evolution :improving , same , worse .
 Symptoms: itch, pain
 Provocative factors , exacerbating and relieving factors
 Previous treatment/s
HISTORY
 Others … hx as in medicine :
 Review of systems: brief for relevant systems (ex : joints , eyes …. )
 Past medical history
 Drug history and allergies.
 Family medical history and history of skin diseases (ex FH of psoriasis or atopy )
 Social history ( animal contact, smoking , travel hx ...)
 Sexual history
EXAMINATION
 Type/s of lesions
 Shape of lesions
 Arrangement
 Distribution
EXAMINATION (T).
 primary lesions :
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Macule/patch: flat ( not elevated ) , alteration of colour or texture
Papule/plaque: raised (elevated) areas without depth
Nodule: solid mass in the skin with significant depth (induration)
Vesicle/bullae/blister: fluid filled spaces.
Pustule/abscess: pus accumulation ( apoptotic cells , debris , and Neutrophils)
Wheal: elevated , white , compressible and evanescent (transient )
Comedon: greasy plug of keratin in pilosebaceous orifice
 Petechiae: pin point bleeding (platelet problem)
 Ecchymosis: large bleeding
 hematoma: bleeding collection , leading to swelling of skin.
(T)
Secondary lesions (modified): 
 Scale : flakes of horney layer ( represents hyperproliferation of epidermis)
 Crust : dried blood or pus or serum (represent damage to skin)
 Lichenification : thickened skin with increased markings (represents repeated
scratching )
 Burrow : gray whitr toutous line (up to 1 cm) , seen in scabies
 Erosion: loss of epidermis only. Heals without scarring.
 Ulcer: loss of epidermis and at least part of dermis. Heals with scar formation.
SHAPE (S)
 Shape of lesion/s:
 Colour
 Surface:
Scaly: papulosquamous disorders
Non scaly: erythemas ( purpuras vs reactive erythemas , to differentiate
between them use diascopy)
 Margin :
Well defined: psoriasis
Ill defined :Eczema
ARRANGEMENT(A)
*Linear: epidermal naevi, kobner phenomenon .…
*Grouped: Herpes simplex
*Annular (ring-like): fungal infection (tinea)
* nummular ( coin-like ) : in discoid eczem
* dermatomal : with hepes zoster (shingles)
DISTRIBUTION(D)
*affected site , ex :
-Localized: unilateral , acral, sun exposed area , ….
- Generalized.
ALSO IN EXAMINATION
*Good light source 
*Examine all skin surface 
*Don’t forget examening hair , nail , mucosa , palmoplantar surfaces , genitalia (if 
needed) . 
SKIN DISEASE CAN BE PART OF SYSTEMIC
DISEASE …
Ex . Patient with butterfly rash on face , arthralgia , oral ulcers … can be SLE . 
Ex2 patient with mouth abd genial ulcers , uveitis … can be becet disease 
Ex3 pt with erythema nodosum , abdominal pain , chronic diarrhea … can be IBD . 
DERMATOLOGICAL INVESTIGATION TOOLS
 Wood’s light: infections, pigmentary problems.
 KOH .
 Diascopy
 Tzanc smear
 Patch test
 Skin biopsy and immunofluorescence.
OTHERVINVESTIGATIONS
 Depending on individual cases :FBC,LFT,KFT,CXR….. .
PAPULES AND PLAQUES
LINEAR EPIDERMAL NAVEUS
ANNULAR
GROUPING
DERMATOMAL
MARGINS WELL-DEFINED
PSORIASIS
SCALY WELL DEFINED MARGINS.
ECZEMA ..ILL DEFINED BORDER
MACULES AND PATCHES
BULLAE
WHEAL
ULCER
FUNGAL HYPHAE
TZANC SMEAR
IMMU FLUO.
The end