Dermatology: Common Skin Disorders & Skin Infections

• What is the structure of skin?

  Epidermis

  
  

  Dermis : contains blood vessels, veins, loose connective tissues, nerves

  
• What is the histology of human skin?

  1. Stratum corneum

  2. Stratum Granulosum

  3. Basal layer

  4.Dermal papilla

  5.Dermis

  
• What is the skin adnexa?

  Skin appendages:

  
  

  anatomical skin-associated structures that serve a particular function including sensation, contractility, lubrication & heat loss in animals e.g. hair, sebaceous/sweat glands
• What else does the skin have apart from the adnexa?

  Complex vascular network which allows the skin to shunt blood to the surface to dissipate heat or retain blood flow deeper in the dermis
• What are the functions of the skin?

  Protection from the environment (chemical, thermal, physical, UV injury)

  
  

  Thermoregulation

  
  

  Neuroreceptor (external stimuli)

  
  

  Antigen processing (Langerhans cells)

  
  

  Synthesis of vitamin D

  
  

  Cosmetic
• History taking in a patient with a skin disorder:

  
• What parts do you have to remember to examine when doing a skin inspection?

  'Hidden sites' e.g. scalp, nails, umbilicus, natal cleft

  
  

  Mucous membranes: oral mucosa, eyes, nasopharynx and sometimes genitalia
• What do you note down when examining a rash of some sort?

  Site: localised, generalised, distribution, skin/mucous membranes

  
  

  Morphology: mono (all the same) /polymorphic (different e.g some might have a blister/erosion, scarring)

  
  

  Background skin: normal/erythema
• What is a macule/patch?

  Flat lesions on skin which are visible as circumscribed areas but are not palpable (able to be touched or felt)

  Macule<1cm

  Patch>1cm

  
• What is a plaque?

  A slightly raised flat topped lesion >1cm diameter

  
• What is a papule?

  A circumscribed palpable elevation <1cm

  These can be itchy & may be associated with lacy white lines or ulcers orally

  
• What might itchy flat-topped papules be?

  Lichen planus
• What is a nodule?

  A palpable elevation >1cm

  
  

  It's black/brown

  
• What is scaling?


  Peeling of the stratum corneum/superficial epidermis

  
  

  Due to dryness of the skin, itchy and dehydrated

  
• What is a vesicle?

  A blister <0.5cm diameter

  
  

  Itchy

  
• What is lichenification & excoriation?

  Lichenification: thickening from scratching is visible here in the popliteal fossa

  
  

  Excoriation: a shallow breach in the surface from scratching often with a haemorrhagic crust

  
• What is a bulla?

  A blister >0.5cm in diameter (intra-orally)

  
• What is an ulcer?

  Full thickness loss of epidermis

  
• What is a scar?

  Permanent change in skin surface/texture

  
• What tests may you need to carry out in order to clarify or confirm a skin diagnosis?

  Skin swabs/scraping: bacteriology, virology, mycology

  
  

  Skin biopsy: histology, culture, immunofluorescence

  
  

  Patch tests: undertaken if contact allergy is suspected

  
  

  Photo-tests: to investigate a possible sensitivity to UV
• If a patient is unwell & either infected or in need of systemic therapy, what blood investigations may be required?

  Haematology: FBC, ESR

  
  

  Biochemistry: U+E, LFT, glucose, CRP

  
  

  Immunology: ANA, DNA, organ specific antibodies

  
  

  Virology: herpes simplex serology
• What are the management options for skin conditions?

  
• What is eczema?


  A pruritic inflammatory condition associated with dryness & erythema of skin

  Scratching results in excoriation & lichenification
• What are some sub-types of eczema?

  Atopic/flexural

  Discoid

  Varicose - poor circulation

  Seborrhoeic

  Lichen simplex

  
• What can eczema be secondarily infected with?

  1. Staphylococcus aureus (impetiginised eczema)- there's yellow crust & weeping

  
  

  2. Herpes simplex (eczema herpeticum)- monomorphic lesions

  
• What 2 situations might dermatitis/eczema be secondary to?

  Irritant contact

  Allergic contact dermatitis

  
• How do you manage patients with eczema?

  Avoid soap, shower gel & contact with irritants such as domestic cleaning agents

  
  

  Advise use of: emollients, topical steroids, oral antibiotics, antihistamines, wet wraps, acyclovir if suspect herpes simplex
• What are the types of psoriasis?

  Psoriasis vulgaris (chronic plaque psoriasis)

  Guttate

  Erythrodermic

  Pustular

  
• What parts of the body are commonly affected in psoriasis?

  The scalp & hairline are frequently affected

  Nail pitting & subungual hyperkeratosis is sometimes present

  
• What are the clinical features of psoriasis?

  Symmetrical well-defined red plaques with thick silvery scale

  
  

  Elbows & knees common sites

  
  

  Lasts for many years
• What does guttate psoriasis look like?

  Raindrop size lesions often follows a streptococcal throat infection

  
• What are the treatments for psoriasis?

  Emollients/bath oils

  Vitamin D analogues e.g. calcipotriol

  Tar preparations

  Topical steroids

  Dithranol

  UVB, PUVA

  Systemic- acitretin, methotrexate, cyclosporin, biologics
• What are the clinical features & variants of lichen planus?

  
• Show some examples of what the different variants of lichen planus look like.

  Results in scarring in some sites

  
• How does oral lichen planus manifest?

  Reticular lichen planus

  
  

  Desquamative gingivitis - bright red, swollen, painful gums

  
• How do you treat lichen planus?

  Topical: emollients, topical steroids (check candida count orally)

  
  

  Systemic: prednisolone, azathioprine/mycophenolate, methotrexate
• What can pruritus be associated with?

  
• pruritus


  itching