Dermatology

Question 1

Causes of erythema multiforme:

Answer 1

1. viruses: herpes simplex virus (the most common cause), Orf*
2. idiopathic
3. bacteria: Mycoplasma, Streptococcus
4. drugs: penicillin, sulphonamides, carbamazepine, allopurinol, NSAIDs, oral contraceptive pill, nevirapine
5. CTD: SLE
6. sarcoidosis
7. malignancy

Question 2

Erythema nodosum causes

Answer 2

1. infection: streptococci, tuberculosis, brucellosis
2. systemic disease: sarcoidosis, inflammatory bowel disease, Behcet’s
3. malignancy/lymphoma
4. drugs: penicillins, sulphonamides, COCP
5. pregnancy

Question 3

Causes of pyoderma gangrenous

Answer 3

• idiopathic in 50%
• inflammatory bowel disease in 10-15%: ulcerative colitis, Crohn’s
• rheumatological: rheumatoid arthritis, SLE
• haematological: myeloproliferative disorders, lymphoma, myeloid leukaemias, monoclonal gammopathy (IgA)
• granulomatosis with polyangiitis
• primary biliary cirrhosis

Question 4

Exacerbating factors of psoriasis

Answer 4

• trauma
• alcohol
• drugs: beta blockers, lithium, antimalarials (chloroquine and hydroxychloroquine), NSAIDs and ACE inhibitors, infliximab
• withdrawal of systemic steroids

Streptococcal infection may trigger guttate psoriasis.

Question 5

Livedo reticularis

1. described as:

Answer 5

1. Livedo reticularis describes an purplish, non-blanching, reticulated rash caused by obstruction of the capillaries resulting in swollen venules.

2. Causes
idiopathic (most common)
polyarteritis nodosa
systemic lupus erythematosus
cryoglobulinaemia
antiphospholipid syndrome
Ehlers-Danlos Syndrome
homocystinuria

Question 6

Skin disorders associated with TB

Answer 6

Lupus vulgaris (accounts for 50% of cases - most common)
erythema nodosum
scarring alopecia
scrofuloderma: breakdown of skin overlying a tuberculous focus
verrucosa cutis
gumma

Question 7

Conditions most associated with onycholysis

Answer 7

idiopathic
trauma e.g. Excessive manicuring
infection: especially fungal
skin disease: psoriasis, dermatitis
impaired peripheral circulation e.g. Raynaud’s
systemic disease: hyper- and hypothyroidism

Question 8

Drugs causing toxic epidermal necrolysis

Answer 8

phenytoin
sulphonamides
allopurinol
penicillins
carbamazepine
NSAIDs

positive Nikolsky’s sign: the epidermis separates with mild lateral pressure

Question 9

Marker of prognosis of malignant melanoma.

Answer 9

Depth of the lesion - Breslow depth