Psoriasis flashcards
15 high-yield MRCP Part 1 cards from the Intellect Medicos Dermatology course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.
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Name four drugs or drug classes that can precipitate or worsen psoriasis.
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Any four of: NSAIDs, ACE inhibitors, beta-blockers, interferon, lithium, antimalarials (e.g. hydroxychloroquine). Abrupt withdrawal of systemic steroids also triggers flares.
Why? These drugs can unmask or flare psoriasis; trauma (Koebner phenomenon) is another trigger.
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What is the NICE first-line topical regimen for chronic plaque psoriasis of the trunk and limbs?
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A potent topical corticosteroid once daily plus a vitamin D analogue (e.g. calcipotriol) once daily, applied separately at different times of day, for up to 4 weeks initially.
Why? The combination works better than either alone. If there is no improvement after 8 weeks, switch to the vitamin D analogue twice daily; after a further 8–12 weeks, a potent steroid twice daily (max 4 weeks) or coal tar.
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What is the first-line systemic (non-biological) drug for extensive or severe psoriasis?
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Oral methotrexate.
Why? NICE recommends methotrexate as the first-choice standard systemic therapy once topical treatment and phototherapy are inadequate.
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How often is oral methotrexate taken for psoriasis, and which supplement is co-prescribed?
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Once WEEKLY (same day each week), with folic acid taken on a different day.
Why? Folic acid reduces mucositis, GI upset and myelosuppression. Accidental daily dosing has caused fatal overdoses.
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Which blood tests are monitored in a patient taking methotrexate?
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FBC, liver function tests and renal function (U&E) — at baseline and regularly throughout treatment.
Why? Methotrexate causes myelosuppression and hepatotoxicity and is renally excreted, so falling renal function raises toxicity.
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Ustekinumab, a biologic for psoriasis, blocks ______; unlike infliximab, etanercept and adalimumab it is not a TNF-α inhibitor.
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interleukin-12 and interleukin-23
Why? Biologics (NICE now says "targeted immunomodulatory treatments") are third line in psoriasis. They are used when conventional systemic drugs and phototherapy have failed or are unsuitable, and the PASI score is 10 or more with a DLQI above 10.
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Which infection must be screened for before starting a biologic such as adalimumab or ustekinumab?
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Tuberculosis (latent TB) — e.g. interferon-gamma release assay and chest X-ray.
Why? Biologics, especially anti-TNF drugs, can reactivate latent TB, often as extrapulmonary or disseminated disease.
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Which HLA allele is most strongly associated with psoriasis?
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HLA-Cw6 (HLA-C*06:02).
Why? It is the main genetic susceptibility allele, particularly for early-onset and guttate psoriasis.
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A 15-year-old develops a sudden eruption of many small, scaly, teardrop-shaped papules over his trunk and limbs. He had a sore throat 3 weeks ago. There was no single larger patch beforehand. What is the most likely diagnosis?
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Guttate psoriasis, triggered by a streptococcal throat infection.
Why? It typically appears 2–4 weeks after a streptococcal sore throat in children and young adults and often clears within a few months. Limited disease: topical treatment; extensive disease: narrowband UVB phototherapy.
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What is the NICE first-line treatment for scalp psoriasis?
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A potent topical corticosteroid once daily for up to 4 weeks.
Why? If there is no response, try a different formulation (e.g. shampoo or mousse) and/or a scale-softening agent (e.g. salicylic acid, an emollient or oil) before applying the steroid.
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What is the mechanism of action of apremilast, used in psoriasis and psoriatic arthritis?
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Oral phosphodiesterase-4 (PDE4) inhibitor — raises intracellular cAMP and reduces pro-inflammatory cytokine production.
Why? It is a non-biological oral option for moderate-to-severe plaque psoriasis and active psoriatic arthritis.
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Secukinumab and ixekizumab, biologics for psoriasis, block which cytokine?
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Interleukin-17A (IL-17A).
Why? IL-17 is a key effector cytokine of the Th17 pathway that drives keratinocyte proliferation in psoriasis.
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Which two adverse effects are routinely monitored in a patient taking ciclosporin for psoriasis?
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Nephrotoxicity (serum creatinine) and hypertension (blood pressure).
Why? Ciclosporin, a calcineurin inhibitor, causes dose-related renal vasoconstriction. Other effects: gingival hyperplasia, hypertrichosis, tremor and hyperkalaemia.
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For how long after stopping acitretin must pregnancy be avoided?
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At least 3 years.
Why? Acitretin is highly teratogenic and can be converted to etretinate (especially with alcohol), which is stored in fat and eliminated very slowly. Contraception starts 1 month before treatment.
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Which commonly prescribed antibiotic must be avoided in a patient taking methotrexate, and why?
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Trimethoprim (including co-trimoxazole) — additive antifolate effect causing severe, potentially fatal bone marrow suppression.
Why? Trimethoprim also inhibits folate metabolism and reduces methotrexate excretion. NSAIDs and penicillins also reduce methotrexate renal clearance.