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What are the histological findings of psoriasis?
Inflammation of the dermal-epidermal junction
Peripheral palisading of basal cells
Acanthosis, Parakeratosis and Munro microabscesses
Question 1 Explanation:
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 is a precursor to squamous cell carcinoma (SCC)?
Question 2 Explanation:
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.
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
Question 3 Explanation:
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 childhood infection is associated with Koplik spots?
Question 4 Explanation:
Measles is a paramyxovirus. Koplik spots are small bright red spots with a white centre on the buccal mucosa that precede the measles rash by 1-2 days and are pathognomonic for measles. Measles present initially with cough, coryza and conjunctivitis then the Koplik spots. Eventually a maculopapular rash develops, beginning at the head/neck and spreading downwards.
What disorder is characterised by an initial ‘herald patch’ which is then followed by scaly erythematous plaques usually in a ‘Christmas tree’ distribution?
Varicella zoster virus
Question 5 Explanation:
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 is the pathogenesis of vitiligo?
Congenital lack of pigmentation
Increase in the number of melanosomes
Autoimmune destruction of melanocytes
Benign proliferation of melanocytes
Question 6 Explanation:
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 infective agent implicated in acne?
Question 7 Explanation:
Propionibacterium acnes infection produces lipases resulting in inflammation and breakdown of sebum, leading to pustule formation.
Do people with albinism have an increased risk of skin cancer?
Question 8 Explanation:
Albinism is the congenital lack of pigmentation. Melanin is protective against UVB, thus persons afflicted with the disorder would be more susceptible to UVB induced DNA damage, increasing the risk of basal cell carcinoma, squamous cell carcinoma and melanoma.
How does lichen planus present clinically?
Salmon coloured plaques with silvery scale
Pruritic, red, oozing rash with edema
Golden coloured crusts
Pruritic, purple, polygonal, planar papules and plaques
Question 9 Explanation:
Learn the 6 P’s of lichen planus. It also often occurs with reticular white lines on the mucosal surfaces (Wickham striae). There is an association with hepatitis C.
An elderly lady presents to her doctor with a raised, round discoloured plaque, ‘stuck on appearance’ on her face. What skin condition is this?
Basal cell carcinoma
Question 10 Explanation:
Seborrheic keratosis is a benign squamous proliferation and is seen frequently in the elderly.
What is the best indicator of prognosis for a melanoma?
Invasion of the dermis
Question 11 Explanation:
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 the most common mole found in adults?
Question 12 Explanation:
A mole/nevus is a benign neoplasm of melanocytes. It can be congenital or acquired. If acquired, it progresses from a junctional nevus (most common in children) to a compound nevus and eventually to an intradermal nevus. Note that the mole can undergo dysplasia and the dysplastic nevus is a precursor to melanoma.
What disease is associated with dermatitis herpetiformis?
Question 13 Explanation:
In coeliac disease, there are IgA antibodies against gluten that cross react with reticulin fibres that anchor the basement membrane to the dermis. Thus, IgA is deposited at the tips of dermal papillae, presenting as grouped pruritic vesicles, papules or bullae. Usually found on elbows.
What type of melanoma is often seen in dark skinned individuals?
Lentigo maligna melanoma
Question 14 Explanation:
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
Question 15 Explanation:
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 is the most common causative agent of erythema multiforme (EM)?
Penicillin and sulphonamides
Systemic lupus erythematosus
Question 16 Explanation:
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 is the pathogenesis of pemphigus vulgaris?
IgG antibody against desmoglein
IgG antibody against hemidesmosome components
Autoimmune deposition of IgA at tips of dermal papillae
Enzyme defect in tyrosinase
Question 17 Explanation:
Desmosomes are located in the stratum spinosum between keratinocytes. Antibodies against the desmoglein component result in painful flaccid bullae or blisters that rupture easily on both skin and oral mucosa. It is treated with corticosteroids.
What condition is associated with acanthosis nigricans?
Type 2 diabetes and gastric adenocarcinoma
Basal cell carcinoma
Question 18 Explanation:
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?
Question 19 Explanation:
Molluscum contagiosum is an umbilicated papule. It is commonly seen in children and sexually transmitted in adults.
What is Leser-Trélat sign?
Sudden appearance of multiple seborrheic keratosis and is an indicator of a gastrointestinal tract carcinoma.
A left supraclavicular node associated with gastric carcinoma
Metastasis of gastric carcinoma to the periumbilical region
Metastasis of gastric carcinoma to the bilateral ovaries
Question 20 Explanation:
Note that the presentation of gastric carcinoma can include Leser-Trélat sign, Virchow node, Sister Mary Joseph nodule and Krukenberg tumour.
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