Principles in Diagnostic Dermatology

• Spot diagnostic approach


  One disease = One classical image

  
• 4 fundamental approaches in diagnostic dermatology

  • Spot diagnostic approach
  • Empirical treatment approach
  • Entrance based approach
  • Advanced skin approach

  
• Spot diagnostic approach is commonly used in professional examination but has much lesser practical value

  
• 4 fundamental approaches in dermatology

  • Spot diagnosis
  • Treatment based approach
  • Entrance based approach
  • Advanced skin approach

  
• Entrance based approach

  Based on morphology, pattern, and distribution
• Elements in entrance based approach

  • Distribution
  • Pattern
  • Local configuration
  • Morphology and its details
  • Morphology and its progression (primary and secondary)

  
• Physical examination of skin

  • Inspection
  • Measurement
  • Palpation
  • Percussion and auscultation
  • Special tests
• Primary and secondary lesion concept in dermatology

  1. Recognize the type of skin lesions

  2. Give them a dynamic life (primary and secondary concept)

  3. Select the more specific and representative lesion to enter

  
• Primary lesions

  • Macule and patch
  • Papule, nodule, and tumor
  • Vesicle and bullae
  • Pustule
  • Wheals
• Secondary lesions

  • Fissure
  • Plaque
  • Excoriation
  • Crusting
  • Erosion and ulcer
  • Granulation tissue
  • Atrophy and hypertrophic scar
• Primary and secondary lesions are the basic building blocks of all skin problems
• Morphological details

  A. Practice regularly

  B. Guidance

  C. Magnifying glass/dermatoscope

  D. Microscopic correlation between eye and brain
• Visual dissection

  • Edge/border
  • Size, shape
  • Surface and depth
  • Color
  • Consistency
  • Appendages
• Atopic eczema

  • Ill-defined
• Psoriasis

  • Well-defined
• Level of pigmentation

  Epidermis: brown to black

  Dermis: greyish to greenish/bluish
• Epidermal lesions

  • Atopic dermatitis
  • Discoid eczema
  • Seborrheic eczema
  • Statis eczema
  • Contact eczema

  Mycosis Fungoides

  • Darier disease
  • Epidermal nevus
  • Viral wart
  • Scabies
• Inflammatory dermatoses

  • Pityriasis lichenoides
  • Psoriasis
  • Pityriasis rosea
  • Pityriasis Rubra pilaris
  • Drug induced papulosquamous eruption
  • Lichen planus
  • Subacute lupus erythematousus
• Fungal infections

  • Tinea infection
  • Candidiasis
  • Pityriasis versicolor
• Viral wart

  • Disrupted skin marking and black dot on surface
• Seborrheic Keratosis

  Benign epidermal "stuck-on" papules with rough, dry, crumbling surface; no malignant potential but can become irritated
• Dermal rashes

  • Granulomas (infectious and non-infectious)

  Malignancy (secondary/leukemic cutis)

  Vascular (vasculitis, Kaposi sarcoma)

  Reactive (annular erythema, urticaria)
• Cellular infiltrates

  • Neutrophils (Sweet syndrome)

  Mast cells (Mastocytosis)

  Plasma cells (Plasmacytoma)

  Eosinophils (Insect bites, Well's syndrome)

  Lymphocytes (T cell/B cell lymphoma, leukemic cutis, lupus tumidus, Jessner lymphocytic infiltrates, histiocytosis)
• Non-cellular infiltrates

  • Solar elastosis, colloid millium, mucinosis
• Erythema Nodosum

  • Inflammation of fat, ill-defined, feel more than see, skin markings stretched but not fully distorted, palpability, color, uniformity, shape
• Consistency of lesions

  • Soft (lipoma, neurofibroma)

  Firm (vascular tumor)

  Firm to hard (dermatofibroma, keloid)

  Hard (gouty tophi, calcinosis)
• Distribution-based approach

  Focuses on 5 elements (skin, hair, nails, mucosa, teeth) and their patterns and local configuration
• Patterns based on distribution

  • Flexural (intertrigo)

  Sun-exposed area

  Palmoplantar

  Acral
• Patterns in sun-exposed areas

  • Connective tissue disease

  Drug-induced photodermatitis

  Genetic (Xeroderma Pigmentosum, Bloom syndrome, Rothmund Thompson)
• Patterns in palmoplantar areas

  • Juvenile palmoplantar dermatoses

  Contact eczema (irritant/allergic)

  Scabies

  Hand foot mouth disease

  Tinea pedis and manuum

  Palmoplantar pustulosis

  Primary palmoplantar keratoderma

  Papular purpuric glove and stocking syndrome (Parvovirus)
• Acral patterns

  • Acrodermatitis Enteropathica

  Gianotti Crosti Syndrome

  Henoch Schonlein Purpura

  Papular Urticaria

  Erythema Multiforme
• Morphological patterns

  • Linear

  Annular

  Arciform

  Polycyclic

  Herpetiform

  Blaschkoid

  Zosteriform

  Iris (target sign)

  Reticulate

  Serpiginous
• Special tests in dermatology

  • Wood light

  Diascopy

  Darier sign

  Nikolsky sign

  Dermascope

  
• Wood light is used to augment the appearance of vitiligo
• Diascopy can distinguish purpura from vasodilation
• Entrance based approach, spot diagnosis, and treatment based approach are the three main principles in dermatology