Dermatology Quiz

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.

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.

Seborrheic keratosis is a benign squamous proliferation and is seen frequently in the elderly.

Propionibacterium acnes infection produces lipases resulting in inflammation and breakdown of sebum, leading to pustule formation.

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).

Molluscum contagiosum is an umbilicated papule. It is commonly seen in children and sexually transmitted in adults.

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.

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.

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.

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.

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.

Note that the presentation of gastric carcinoma can include Leser-Trélat sign, Virchow node, Sister Mary Joseph nodule and Krukenberg tumour.

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).

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.

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.

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.

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.

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.

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.