Dermatology Flashcards
What is the pathogenesis of vitiligo?
- Congenital lack of pigmentation
- increase in numbers of melanosomes
- Autoimmune destruction of melanocytes
- benign proliferation of melanocytes
Vitiligo is the localised loss of skin pigmentation due to the autoimmune destruction of melanocytes. Melanocytes synthesise melanin in melanosomes. Thus, if melanocytes are destroyed, melanin cannot be produced.
What is the most common causative agent of erythema multiforme (EM)?
- penicillin and sulphonamides
- Systemic lupus erythematosus
- HSV infection
- malignancy
HSV is the most common etiologic agent of EM, which presents as a targetoid rash and bullae. All the other options are also associated with the disorder, but less commonly.
What disorder is characterised by an initial ‘herald patch’ which is then followed by scaly erythematous plaques usually in a ‘Christmas tree’ distribution?
- Pityriasis rosea
- Herpes
- Erysipelas
- Variceller zoster virus
Pityriasis rosea classically presents with a salmon coloured solitary patch ‘herald patch’ which enlarges over a few days followed by generalised bilateral and symmetric macules with collarette scale. Pruritus is sometimes present. It self resolves within 6 – 8 weeks.
What are the histological findings of psoriasis?
- inflammation of dermal-epidermal junction
- Peripheral palisading of basal cells
- Acanthosis, Parakeratosis and Munro microabscesses
- keratin psuedocysts
Psoriasis is as a result of increased keratinocyte proliferation. It presents as salmon coloured papules and plaques with silvery scaling, especially on extensor surfaces and scalp. On histology, there is epidermal hyperplasia (acanthosis), hyperkeratosis with retention of nuclei in stratum corneum (parakeratosis) and groups of neutrophils in the stratum corneum (Munro microabscesses).
What type of melanoma is often seen in dark skinned individuals?
- superficial spreading
- Lentigo maligna melanoma
- Acral lentiginous
- nodular
The acral lentiginous variant of melanoma arises in dark skinned individuals on their palms or soles. It is not linked to UVB induced DNA damage unlike the other types (this was the disease that caused the death of Bob Marley).
How does impetigo present?
- golden honey coloured crust over an erythematous base
- Salmon coloured plaque with silvery scale
- comedones, pustules and nodules
- Flesh coloured papule with a rough surface
Impetigo is a superficial skin infection caused by Staph aureus or Strep pyogenes. It frequently affects children. It is treated with penicillin and topical preparations e.g. mupirocin.
What condition is associated with this presentation? A pink pearly nodule with telangiectasias, ulceration and rolled borders on the upper lip.
- squamous cell carcinoma
- basal cell carcinoma
- melanoma
- eczema
This is a classical presentation of basal cell carcinoma, a malignant proliferation of basal cells and the most common skin cancer. Risk factors include excessive sunlight exposure, xeroderma pigmentosum and albinism. Treatment is surgical excision.
What is the best indicator of prognosis for a melanoma?
- asymmetry
- colour
- diameter
- Invasion of the dermis
Invasion/ depth of extension measured by Breslow thickness is the most significant prognostic factor in predicting metastasis. Asymmetry, border irregularity, colour variation and diameter (>6mm) are known as the ‘ABCD’ criteria for describing melanomas.
What is a precursor to squamous cell carcinoma (SCC)?
- keratoacanthoma
- actinic keratosis
- Leser-Tralet sign
- measles
Actinic keratosis is a premalignant lesion to SCC, caused by prolonged sun exposure. It presents as scaly, rough, erythematous and small plaques, most commonly on the face, back or neck.
An elderly lady presents to her doctor with a raised, round discoloured plaque, ‘stuck on appearance’ on her face. What skin condition is this?
- rubella
- seborrhiec keratosis
- basal cell carcinoma
- melasma
Seborrheic keratosis is a benign squamous proliferation and is seen frequently in the elderly.
What condition is associated with acanthosis nigricans?
- type 2 diabetes and gastric adenocarcinoma
- rubella
- varicella zoster
- basal cell carcinoma
Acanthosis nigricans is epidermal hyperplasia with darkening of the skin, especially in the axilla, neck or groin. It is associated with malignancy especially GIT adenocarcinoma or insulin resistance as seen in type 2 diabetes and metabolic syndrome.
What skin condition is caused by poxvirus?
- verruca
- impetigo
- cellulitis
- Molluscum contagiosum
Molluscum contagiosum is an umbilicated papule. It is commonly seen in children and sexually transmitted in adults.
