Dermatology Flashcards
What is Acne? Describe the pathophysiology.
= a common chronic disorder affecting the hair follicle & sebaceous gland (pilosebaceous unit), in which there is expansion & blockage of the follicle & inflammation.
The earliest change in acne is the formation of microcomedones:
- Normally when keratinocytes die, they separate from each other in the process of desquamation.
- In acne, this process is abnormal, causing the dead keratinocytes to stick together, along with the increased sebum, to form a plug at the top of the hair follicle.
- Androgens cause increased sebum production, which increases the chance of this process occuring.
- As the plug gets larger, it becomes more visible.
- Whiteheads are closed comedones, and blackheads are open comedomes with dilated opening filled with dead cells & sebum (the black part is melanin).
- When the comedone’s rupture & burst, an inflammatory response is evoked.
What medications can be given for moderate-severe acne?
- 1st line → 12 weeks combination therapy
- Topical adapalene (retinoid) + topical benzoyl peroxide + oral lymecycline/doxycycline
- COCP (in women) + topical benzoyl peroxide
What medications can be given for mild-moderate acne?
- 1st line → 12 weeks of topical combination therapy
- Adapalene (retinoid) + benzoyl peroxide
- Benzoyl peroxide + clindamycin
NB: retinoid is best agent to start with in those with predominant comedonal acne
What bacteria is found in higher numbers on the skin of those with acne?
Propionibacterium Acnes
What is psoriasis? Briefly describe the pathophysiology.
= a chronic autoinflammatory skin condition, characterised by clearly defined, red & scaly plaques.
- The immune system is disordered, causing inflammation within the dermis. This results in hyperproliferation of keratinocytes.
- Vesicles of neutrophils also develop, which are sterile inside → present as pustules in the skin
What is the most common form of psoriasis in adults?
Stable chronic plaque psoriasis
What conservative managements are recommended for psoriasis?
Conservative:
- Reduce smoking or alcohol
- Treat any untreated HIV
- Change any drugs which may be triggering disease
What topical treatments can be given for psoriasis?
- Emollients → with or without salicylic acid (helps with plaques/scales & itch)
- Corticosteroids → reduce place thickness, scaling, erythema
- Vitamin D analogues → inhibits epidermal hyperproliferation
Regime
Start with corticosteroids & vitamin D OD. After 8 weeks, give a 4-week treatment break of the steroids, and continue just the vitamin D BD. Corticosteroids may be restarted after this.
What antibiotic is given for cellulitis if someone has a penicillin allergy?
Doxycycline
Describe the pathophysiology of scabies.
Scabies = tiny mites called Sarcoptes Scabiei that burrow under the skin causing infection & intense itching.
Pathophysiology:
- The rash & intense itch occurs due to the development of a delayed hypersensitivity reaction to mite eggs & faeces.
- As scabies is a cell-mediated response, the immune response which produces the clinical symptoms will only become apparent ~3 weeks following infestation.
How does scabies present?
- Severe pruritis, worse at night
- Close contacts with similar symptoms
- Rash is variable, but is erythematous papules or vesicles, and surrounding dermatitis.
- Burrows → small irregular tracks, ~1cm in length, classically found in webbed spaces between the fingers
- Crusted/Norwegian scabies → severe variant where a person is infected with thousands or millions of mites.
How is scabies managed?
- Permethrin cream → apply to whole body, completely covering the skin.
- Best to do this when this skin is cool
- Leave on for 8-12 hours & then wash off
- Repeat a week later.
- Oral ivermectin → single dose, repeated a week later is an option for difficult to treat or crusted scabies
- Treat all household contacts the same, even if asymptomatic.
- Crotamiton cream & chlorphenamine → at night can help with itching
Itching can continue for up to 4 weeks after successful treatment.
What is the range of steroid creams?
Mild -> 1% hydrocortisone
Moderate -> eumovate
Potent -> betnovate
Super potent -> dermovate
What is eczema herpeticum & how does it present? How is it treated?
= a viral skin infection, which usually occurs in a patient with pre-existing dermatitis, caused by HSV or varicella zoster virus.
- widespread, painful, vesicular rash
- systemic symptoms - fever, lethargy, irritability
Treated with oral or IV aciclovir.
How does a Basal Cell Carcinoma present? How is it managed?
- Translucent, shiny quality
- Pearly papules surrounding an ulcerated crater
- Telangiectasias
- Location → face, scalp, back, legs, arms. Sun exposed areas.
- Size → <1cm typically, but can be larger (>5cm).
- Growth → slow, over many months/years
- Pigmented BCC can be hard to distinguish from melanoma; err on the side of caution
Management:
- Biopsy → confirm histopathology
- Excision → with 4mm margin, tends to be 1st line
