Dermatology Flashcards
How are nail clippings collected?
- Can be used on finger or toenails
- The nail sample should be taken from the area of
deformity/ discolouration and cut back as much as
possible and through entire thickness of nail of a
good sample. - Sample collected in dermapak for transport.
- If not
available, then in paper towel and in sterile
universal pot. - Normally takes ~4-5 days for culture results
What are nails clippings used to differentiate between?
Differentiate between fungal and dystrophic nails/
other pathology
When do you use skin scraping?
- If unknown skin rash
- Rash not responding to treatment.
What can skin scraping be used to diagnose?
- Mainly used for fungal skin infection
- Detects scabies/bacterial infection
What investigations are carried out with skin scrappings?
microscopy & culture
How is skin scrapping performed?
- 70% alcohol wipe used to clean skin to avoid contamination/ aid microscopy if creams on the skin.
- Sterile scalpel blade used to take a superficial scraping of the skin of the rash/ affected area of
concern. - Sample put into dermapak for transport to the lab or wrap in paper towel and put into sterile universal sample pot.
How long does skin scrapping results take?
4-5 days
What is wood’s lamp?
Handheld device emits long wave ultraviolet light.
Aka blacklight as little light seen to the naked eye
How is wood’s lamp carried out ?
Used in a darkened room over area of skin of concern to help in diagnosis. Abnormal skin will become fluorescent.
What is wood’s lamp used to diagnose?
- Fungal infections of the skin (green/blue)
- Bacterial infections of the skin (coral red)
- Vitiligo (blue/white)
- Head lice
- Other pigmented lesions
Use of wood’s lamp in diagnosis
- Can strengthen or lessen suspicion of a diagnosis
depending on the colour of the fluorescence of the skin. - Normal skin will not fluoresce
Indications for allergy testing
- Previous symptoms of Anaphylaxis – URGENT ALLERGY
- Food allergy suspected
- Drug allergy suspected
- Urticaria/ angioedema: acute and chronic
- Asthma: unexplained deterioration/ uncontrolled
- Allergic rhinitis: severe symptoms/ not controlled on standard treatment.
- Eczema/ dermatitis: where allergic cause possible e.g unexplained deterioration/ more
frequent unexplained flare ups/ not controlled with standard treatment.
Types of allergy testing
- Skin prick test
- Skin patch test
- RAST/Immunochap (blood test)
- Food Challenge
How is skin prick test carried out?
- Start by taking history and deciding what allergens to test for
–> can have
false positive results so avoid testing
allergens not indicated - Suspected allergen applied to the skin
(normally forearm) - lancet used to prick the skin.
- Reaction measured in 10-15
minutes. - Negative (saline) and positive
(histamine) controls used.
Where is skin prick test carried out and why?
Performed in hospital environment due
to very rare but hypothetical risk of
anaphylaxis reaction.
When do you use skin patch test?
Used for delayed/ contact reactions of the
skin. e.g. contact dermatitis.
Where is skin patch test carried out?
Performed in hospital/ clinic setting.
How is skin patch test carried out?
- Common allergens that come into contact
with the skin + others from history taken are
applied onto the skin with small disc patches
and held on with hypoallergenic tape. - 3 appointments in a week. - Initial appointment will apply the allergens.
- Second appointment in 2 days after patches applied to remove the discs and assess reactions.
- Third appointment 4 days after patches applied to assess for delayed reactions. - Positive test- red/ raised/ reaction formation
on area of patch.
What is RAST/immunochap?
Blood test for to measure IgE antibodies to an allergen.
Why is RAST/immunochap carried out?
Testing IgE to allergen often used to confirm if reaction is a false positive if unexpected
reaction on skin prick test. Ie someone able to eat said allergen but forms skin reaction.
When is RAST/immunochap indicated?
Can be used if skin prick test cannot be used
(Give equivalent information to skin prick but more expensive, cannot get results on the
same day and less acceptable especially for children.)
How do you describe a rash/mole?
ABCDE criteria
A- Asymmetry B- Border C- Colour D- Diameter (largest diameter more than 7mm) E- Evolution
Indications for 2WW referral in derm
Red flags of skin lesions/ suspected cancer:
- Melanoma
- Squamous Cell Carcinoma
- Cutaneous T-cell lymphoma
- Kaposi’s sarcoma
If 100% sure lesion in keeping with Basal Cell Carcinoma- routine referral to dermatology as
slow growing.
–> In reality would refer any lesions with red flags via 2ww pathway
What is a dermatoscopy?
- Easy to use and light weight microscope- high quality
lens that can magnify up to 10-14 times that of the
naked eye - Allows visualisation of subsurface patterns/
pigmentation and structures not seen by the naked
eye. - Come in small handheld devices/ attachable
accessories for phones.
