Angioedema, porphyria & MetHb flashcards
12 high-yield MRCP Part 1 cards from the Intellect Medicos Haematology & Oncology 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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What is the best screening blood test for hereditary angioedema?
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Serum C4 — low, even between attacks.
Why? C1-inhibitor deficiency allows unchecked complement activation, consuming C4.
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What treats an acute attack of hereditary angioedema?
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C1-esterase inhibitor concentrate or icatibant (bradykinin B2 receptor antagonist).
Why? HAE swelling is driven by excess bradykinin (from unchecked kallikrein), so treatment replaces C1-INH or blocks bradykinin.
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What is the treatment of symptomatic acquired methaemoglobinaemia?
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IV methylene blue.
Why? Methylene blue speeds the reduction of ferric (Fe3+) haem back to ferrous (Fe2+), restoring oxygen carriage.
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Name three drug groups that can precipitate an attack of acute intermittent porphyria.
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Any three of: barbiturates, oral contraceptive pill, halothane, alcohol, sulphonamides, benzodiazepines (also enzyme inducers such as rifampicin, phenytoin, carbamazepine).
Why? These induce hepatic ALA synthase, increasing production of toxic haem precursors (ALA and porphobilinogen).
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What is the diagnostic test in a suspected acute attack of acute intermittent porphyria?
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Urinary porphobilinogen (raised).
Why? Porphobilinogen deaminase deficiency causes porphobilinogen and ALA to build up and spill into the urine.
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What is the definitive treatment of an acute porphyria attack?
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IV haem arginate (haemin).
Why? Giving haem switches off hepatic ALA synthase through negative feedback, stopping precursor production.
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Which antihypertensive drug class causes non-histaminergic angioedema, and by what mechanism?
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ACE inhibitors — they block the breakdown of bradykinin, which accumulates.
Why? ACE normally degrades bradykinin, a vasodilator that increases vascular permeability.
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What is the gold-standard investigation for methaemoglobinaemia?
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Co-oximetry (on a blood gas sample), measuring the methaemoglobin percentage.
Why? Pulse oximetry cannot read methaemoglobin correctly, so SpO2 is low while PaO2 is normal — a "saturation gap".
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Name three drugs that can cause acquired methaemoglobinaemia.
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Any three of: dapsone, local anaesthetics (benzocaine, prilocaine, lidocaine), nitrates/nitrites, primaquine, chloroquine, sulphonamides, rasburicase.
Why? These oxidise haem iron from ferrous (Fe2+) to ferric (Fe3+), which cannot carry oxygen.
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Which enzyme is deficient in porphyria cutanea tarda, and what is the first-line treatment?
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Uroporphyrinogen decarboxylase; venesection (low-dose hydroxychloroquine is an alternative).
Why? Iron overload drives the disease; removing iron, stopping alcohol and sun protection reduce the blistering.
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A 30-year-old with EBV infection develops persistent fever, splenomegaly and pancytopenia. Ferritin is 45,000 µg/L, triglycerides are high and fibrinogen is low. What is the diagnosis and first-line treatment?
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Haemophagocytic lymphohistiocytosis (HLH) — dexamethasone and etoposide (treat the trigger).
Why? Uncontrolled activation of macrophages and cytotoxic T cells causes a cytokine storm; macrophages engulf blood cells.
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What infection prevention is advised after splenectomy?
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Pneumococcal (PCV20) and meningococcal (ACWY and B) vaccines, yearly influenza vaccine, and antibiotic prophylaxis (usually phenoxymethylpenicillin).
Why? Without the spleen, encapsulated bacteria can cause overwhelming post-splenectomy infection (OPSI).