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Dermatology Undergraduate Review

Dermatology Undergraduate Review. Dr J. T. Lear Consultant Dermatologist, Manchester Royal Infirmary. Overview. Layers Turnover Embryology Nails / Hair Glands Melanocytes. Layers. Surface area skin 1.8 sq. metres, 16% body weight

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Dermatology Undergraduate Review

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  1. Dermatology Undergraduate Review Dr J. T. Lear Consultant Dermatologist, Manchester Royal Infirmary

  2. Overview • Layers • Turnover • Embryology • Nails / Hair • Glands • Melanocytes

  3. Layers • Surface area skin 1.8 sq. metres, 16% body weight • Layers - Epidermis, Dermo-epidermal junction, Dermis, Subcutaneous Fat, Fascia, Muscle

  4. Maturation • Keratinocytes mature from bottom to top • basal cell layer, prickle cell layer, • granular layer (lose nuclei), horny layer • Basal layer replication rate – 200-400 hours.

  5. Maturation / Dermis • Cell turnover 28 days – 14 for maturation, 14 for shedding • Dermis – collagen fibres 70%, elastin, ground substance, fibroblasts, dendrocytes, mast cells, macrophages, lymphocytes

  6. Embryology • epidermis develops at 4 weeks, • nails take shape 10 weeks, • dermis 11 weeks, • hair bulbs 12 weeks, • fingerprints 17 weeks

  7. Nails • Dense keratin • Matrix – dividing cells, nail plate, nail bed, hyponychium • Grow at 0.1mm / 24 hours fingers (toes slower) • Lunula – distal visible part of the matrix

  8. Hair (1) • Lanugo – shed after birth • Vellus – short, fine • Terminal – longer, thicker

  9. Hair (2) • Outer cuticle, • inner medulla. • Arrector pili muscle – goose pimples

  10. Hair (3) • Growth Cycle - Anagen – growing phase – 3-7 years. • 90% scalp hairs anagen at any one time • Scalp growth 0.4mm / 24 hrs

  11. Hair (4) • Catagen • resting phase – 3-4 weeks • 10-20% scalp hairs catagen at any one time

  12. Hair (5) • Telogen • shedding phase. • 50-100 scalp hairs shed each day. • <1% scalp hairs telogen at any one time

  13. Glands • Sebaceous glands – androgen sensitive • Sweat glands – • eccrine, apocrine (axilla, perineum, areola) • Sympathetic innervation. • Sweat isotonic, high K+, lactate, urea. • Minimum insensitive perspiration 0.5 l / 24 hrs

  14. Pigmentation (1) Melanocytes • Basal Layer. • Produce melanin in melanosomes from tyrosine via tyrosinase. • Transferred by phagocytosis to keratinocytes.

  15. Pigmentation (2) • Protection against UV. • Different races – different size and number of melanosomes, not melanocytes

  16. Mosaicism • Mosaicism and Blaschko’s lines

  17. Clinical Overview • Usually common conditions • Or rare but important from diff. diagnosis viewpoint • Cover psoriasis, eczema, itching, acne, tumours, auto-immune assocd. conditions • Leaves just ~3000 others for you to read about!!

  18. Psoriasis - Definition • Chronic, non-infectious • Inflammatory dermatosis • Well demarcated, erythematous plaques • Topped with silvery scale

  19. Psoriasis - Epidemiology • 2% European population (less Africa,Japan) • Sexes equally • Peak onset 2nd/3rd decade • 2nd peak 50-60’s • Unusual children <8

  20. Pathogenesis • Precipitating factors • Trauma – Koebner • Infection • Drugs – B-block, lithium, anti-malarials • Sunlight – 10% aggravated • Stress - ?relevant

  21. Psoriasis – Clinical Features (1) • Plaque • Guttate • Flexural • Localised • Generalised Pustular • Nail • Erythroderma

  22. Plaque Psoriasis • Well defined, disc shaped plaques • Elbows, knees, sacrum, scalp • Pin point bleeding when remove scale • Symmetrical, sometimes itchy • Diff. – drugs, hypertrophic l.p.

  23. Guttate Psoriasis • Drop-like lesions trunk/limbs • Adolescents / young adults • Following strep. Infection • Diff. – pityriasis rosea

  24. Flexural Psoriasis • Axillae, sub-mammary fold, natal cleft • Smooth, glazed • Most often elderly • Diff. - candidiasis

  25. Localised Psoriasis (1) • Palmo-plantar pustulosis • Yellow/brown sterile pustules palms and soles • Minority plaques elsewhere • Middle aged females who smoke • Highly symptomatic, persistent • Diff. - hyperkeratotic eczema, Reiter’s

  26. Nail Psoriasis • 50% of cases • Pitting, onycholysis (salmon pink) • Subungual hyperkeratosis, espy toes • Often assocd. with arthropathy • Diff. - fungal

  27. Psoriatic Arthropathy • 5% of cases • Distal – commonest pattern • RA like • Mutilans • Oligo • Ank spond – hla b27

  28. Psoriasis – Management • ????????????????

  29. Eczema classification • Exogenous irritant dermatitis • Allergic contact dermatitis • Endogenous eczema • Atopic • Seborrhoeic dermatitis

  30. Eczema classification •  Asteatotic eczema • Discoid eczema • Pityriasis alba • Hand eczema • Gravitational eczema

  31. Seborrhoeic dermatitis • Differential diagnosis • Psoriasis, lichen simplex, pityriasis rosea, tinea, candida, • allergic contact dermatitis, drug eruptions

  32. Pompholyx • Resolution with desquamation within 2 to 3 weeks • Recurrent attacks • 80% of patients only hands involved • Can see secondary infection • Nail dystrophy with ridging, pitting, thickening and discolouration • More common in warm weather

  33. Atopic dermatitis • Drug sensitivity more common • Food allergy more common • 10% of babies • Urticaria more common • Bacterial infections more common

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