Introduction to clinical dermatology

1. Introduction to clinical dermatology Structure,function,History and Examination and diagnostic approach

2. Basic skin structure • 2 layers: Epidermis and Dermis • Epidermis: All Cells • Dermis: variable • Fibers: collagen and elastin • Ground substance • Cells: Fibroblasts, Lymphocytes, Macro, Mast cells.. • Appendages: Glands ( sebaceous, Apocrine and Eccrine), Hair follicles and Nails • Nerves, lymphatice, vasculature, smooth muscles

3. Epidermis 1ALL CELLS • 4-Cell layers (Keratinocytes): • Basal layer: single row of columnar epithelium. In normal skin cell mitosis takes place in this layer ONLY • Prickle(spinous,squamous) layer: Several layers (5-8) of cells tightly bound by Desmosomes. In cases where there is a problem involving Desmosomes cell separation results (Acantholysis)

4. Epidermis 2 • Granular layer: • 2 types of granules: keratohylin (Ptn)and Odland granules (Lipids and Hydrolytic enzymes) • Horney layer (Stratum Corneum): • Dead Cells (No Nuclei) called Corneocytes • This is the most important layer as Barrier function of the skin depends on the presence of intact Horney layer

6. Basic Histology of skin

7. Epidermis 3Proliferation and Desquamation • In normal skin cell division only takes place within Basal cells • 1/3 of Basal cells are dividing. 2/3 are resting • The cell takes about 60 days to get from Basal layer to surface of Horney layer • Hydrolytic enzymes from Odland granules dissolve lipids cementing between corneocytes leading to desquamation of old degenerate cells

8. Epidermis 4other cells • Melanocytes: Dendretic • Derived from neural crest • Within Basal layer • Produce melanin which is then transferred to KC • Langerhanscells: Dendretic • Skin tissue macro • APC of both epidermis and dermis • Present throughout epidermis • Merkel cells: non-Dendretic • Transducers for fine touch • At Basal layer

9. Melanocytes and epidermal melanin unit

10. Dermis 1 • Fibers: • Collagen type 1 is the predominant type. Collagen 3 is mainly present in upper (papillary dermis). Elastin is found associated with Collagen bundles • Ground substance: GAG • Cells • Fibroblasts: produce Fibers and Ground substance • Mast cells: sore Histamine which upon release causes vasodilatation and Bronchoconstriction (anaphlaxis) • Appedages: • Nerves, vessels, muscles..

11. Skin as a Barrier • The main function of skin to prevent entry of foreign things into internal environment • Horney layer is the main structure responsible for this • Problems and diseases affecting Horney layer will impair this function leading to infections, allergies…

12. Skin immune system1components • Epidermal: • Physical Barrier of Horney layer • Langerhans’ cells: • The main APC • Has MHC-2 • Releases various mediators • Keratinocytes: • Can become an APC • Releases various mediators • Dermal: • Langerhans’ and other macrophages • T-Lym and other T cells • Mast cells

13. Skin immune system2immune reactions • The interaction between skin immune system and a foreign material results in an immune reaction • This interaction takes place only if this material penetrates into viable skin (defect in Barrier) as immune cells are not present within Horney layer

14. Type 1 HSR (Immediate type) If an ag interacts with IgE attached to a Mast cells leading to release of Histamine and other mediators Clinical examples include Urticaria and Anaphylaxis Skin immune system3types of reactions

15. 2. Type 2 (Hummiral cytotoxic): IgG/IgM bind to tissue fixed antigen. This activates complement system and damage happens as a result to inflammation Pemphigus and BP… Skin Immune system 4Immune rxns

16. Skin immune system 5Immune rxns • Type 3 : Immune complex Disease: IgG Directed/binds to circulating antigrn/or other antibody: vasculitis and immune complex disease. The damage happens when immune complexes sit/deposit usually in areas where circulation is tight or not moving enough: Kidneys, skin capillaries and lower extrimities

18. Type 4 HSR (Delayed /celluar): this is the only type where cells rather than antibodies are involved. The cells are lymphocytes and macrophages. Examples: ACD, Granulomas, .. Immune reactions 6

19. Derm. History 1 • Chief complaint +Duration: • Rash: multiple red things with/out scale • Lesion: one or few things • Others: as appropriate ( e.g hair loss, blisters, color change…)

20. Derm HX 2 • Analysis of the complaint: • Onset : site where it started and how • Progression: increasing/decreasing/same and which sites • Modifying factors: • Symptoms: itch, pain • Recent illness: viral/fevers.. • Atopy: asthma+eczema+hay fever (personal or 1st degree relative) • Drugs used

21. Derm HX 3 • R.O.S: Related • Past Hx: as per others • Family hx • …

22. Derm Exam • T. SAD: • Type: primary vs secondary (modified..scratched, traumatised…) lesion • Macule/patch: pigmentary disorder or resolving papulosq • Scaly papules/plaques: papulosquamous condition • Non scaly papules/plaques: reactive erythema • Bullae/vesicles: bullous dis….

25. Derm exam • Shape: details of the primary lesion • Color: • red: more RBC.s(Hb) eithre intravascular(dilated vessels) or extravascular (hemorrhage) • Brown/black: melanin • Yellow: carotene (Horney layer and sc fat) • Exogenous…. • Surface: • Scaly: papulosqumaous • Non scaly. • Margins: well defined vs ill-defined (esp important for scaly rashes)

26. Derm exam • Arrangement: • Grouped: grouped vesicles (Herpes), Linear ( plane warts, Kobner… • Distribution: • Unilateral: infection, contact… • Bilateral: inflammatory • Hands/face:sun exposed (photodermatpses/photoaggravated dermatoses).

27. Linear arrangmemnt VEN Plane warts

28. Grouping

29. Red NON-Scaly rash • Red is BLOOD. This is either • Intra vascular: dilated vessel due to usually release of inflammatory mediators (histamine..) DIASCOPY……….BLANCHABLE DDX: Reactive Erythema: EM/EN/URT • Extra vascular: Hemorrhage • Vessel wall injury: vasculitis • Bleeding tendency or due to trauma… DIASCOPY……….NON-BLANCHABLE

30. Red NON-Scaly Algorhythm

31. Red non scaly

32. Patients with Red scaly rashes(papulosquamous) • Scale is flake (piece) from horney layer. • Usually indicates hyper-proliferation of epidermis • The group includes many conditions but commonest are: • Eczema - Lichen Planus • Psoriasis - Fungal infections -Pityriasis Rosea

33. Scaly rashes

34. Scaly bilateral and well defined margins. Extra features:

35. Diagnostics • Wood’s light • KOH • Diascopy • Tzanck smear IF (Direct: tissue and Indirect: plasma) Patch Test

36. Wood’s light • Source of UVA (365 nm) • diagnosis of some infections: • Tineacapitis: green flu on hair shaft • P. Versicolor: golden yellow • Pitryosporum: orange • Pseudomonas: blue • Pigmentary disorders: • Hypopigmentation (pale) vsDepigmentation (chalky white) • Hyperpigmentation: good enhancement (epidermal/good prognosis) vs poor enhancement (dermal pigment/poor prognosis )

37. Diagnostic toolsFungal Hyphae

38. Other diagnostic tools Herpes Tzanck Giant multinucleate cells

39. IF test The test is used to detect immune reactants (abs) directed against various targets so the test is used in conditions where abs are deposited e.g: Pemphigus, Pemphigoid…