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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 : 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
