22.6 From Pyrin to Amyloid

Three short movements: the case, the anatomyThe study of the structure of the human body. and physiologyThe study of how the body functions., then the tie back to Stina. Each links to the scene where you’ll see it move.

I · A flower and a doctor willing to read page two

Colchicine is a small white pill from the autumn crocus, the standard treatment for this disease since the 1970s, old and cheap. Six weeks in, the fevers were further apart and softer when they came; one Tuesday she noticed it was Tuesday and she felt fine and could not remember the last attack. Her CRP was 3. Her serum amyloid A was falling but not yet normal, and the protein in her urine had stopped climbing. The good news and the rage come in the same pill; she takes them both with breakfast. If the SAA will not settle on a full dose, the next step is an IL-1 blocker, and the kidney will be checked every six months for the rest of her life. There is no guideline for her pairing of genes. Her doctor calls it a study of one.

See it move: Scene 1 · The Brake That Is Off · Scene 5 · Two Places to Starve the Fire

II · The pathway, hour by hour

Step one is a trigger — stress, a cold, a period, exertion, cold weather, surgery, or nothing at all — that nudges the innate arm the way it nudges everyone’s. Step two is the sensor. Pyrin, in the neutrophil and the monocyte, normally sits braked by a cellular switch (RhoA) and fires only when a bacterial toxin cuts the brake; the FMF variants loosen the brake so that the nudge is enough. Pyrin assembles with the adapter ASC and the enzyme caspase-1 into the inflammasome; caspase-1 cleaves pro-IL-1β to IL-1β and opens the cell so it pours out. Step three is the cascade: hours 0–2, IL-1β floods the tissue and blood; hours 2–6, it recruits other cellsThe basic structural and functional units of life. to make IL-6 and TNF-α and the signal spreads; hours 6–12, vessels dilate, neutrophils march (Chapter 4), the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions. resets, and the fever spikes. Step four is serositis: IL-1β and its cascade target the serous membranesThin tissues that line body cavities and secrete fluid. — peritoneumThe membrane lining the abdominal cavity and organs., pleuraThe double-layered membrane surrounding the lungs and lining the thoracic cavity., pericardiumThe membrane surrounding the heart., synovium — which inflame, leak an effusion, and turn every movementA fundamental property of life involving motion of the body or its parts. into friction and pain. Step five is the peak at twelve to forty-eight hours: fever to 40, a belly that mimics appendicitis, a chest that stabs with each breath, one hot joint. Step six is resolution at twenty-four to seventy-two hours: inflammasome components run out, IL-10 and regulatory T cells damp the signal, the neutrophils are spent, and the fire burns out for want of fuel. Her second gene adds a hypothesis the case keeps labelled as one: LPIN2, the Majeed gene, encodes lipin-2, whose absence lets the NLRP3 inflammasome and IL-6 run hot; one copy usually does nothing, but a half-expressed LPIN2 beside a half-expressed MEFV may be two atypical diseases amplifying each other — and the reason neither looked textbook enough to be named for forty-nine years. The story’s model, not a published finding.

See it move: Scene 1 · The Brake That Is Off · Scene 2 · Hour Zero to Hour Seventy-Two · Scene 3 · Two Genes, One Fire

III · The slow fuse, and the two cuts

Every flare’s IL-1β and IL-6 reach the liver, and the liver answers with the acute-phase proteinsLarge molecules made of amino acids with various functions in the body.: CRP, which falls when the flare does, and serum amyloid A, which falls more slowly and, when the flares never stop, never quite returns. SAA that stays high for years misfolds, fragments, and stacks into fibrils — AA amyloid — that deposit around the vessels of the gut wall (Chapter 17’s re-stained biopsy), in the mesangium and capillary walls of the glomerulusA network of capillaries in the nephron where blood filtration occurs. (Chapter 19’s Congo red, apple-green under polarizedA resting neuron’s membrane with a more negative charge inside than outside. light), and in the spleen, the liver, the heart. The kidney is where it kills: protein leaks, albuminA plasma protein that helps maintain osmotic pressure and transport substances. falls, ankles swell, and without treatment the filter fails. Before colchicine, up to sixty percent of FMF patients died of that. The chain can be cut at two points. Colchicine binds tubulin, stops microtubules assembling, stops neutrophils crawling and keeps pyrin’s brake on; taken daily — never only during attacks, because it prevents and does not treat — it stops flares in 60–70% and nearly all amyloidosis. For the 5–10% it fails, the second cut is IL-1β itself: anakinra, a daily receptorA structure that detects stimuli. blocker; canakinumab, a monthly antibody against the cytokine; rilonacept. They do not fix the gene; they starve the fire of its signal, and the liver, hearing nothing, stops making the deposit. Monitoring is the kidney, every six months: creatinine, urine protein, and SAA — the number that says whether the fuse is still burning.

See it move: Scene 4 · From SAA to Amyloid · Scene 5 · Two Places to Starve the Fire

5 scenes. Each one has a short animation or a slide, something to explore, a true/false spot-check of your thinking, and a quick check. Every scene gives you an evidence card for your board.

Every scene gave you an evidence card, and the chart adds more. Sort each card into the column it supports: The drug is working upstream of the signal, slowly, Neither on its own, or The drug is masking the fever while the disease runs on. Some cards can honestly go in more than one place — that’s allowed, and the feedback tells you which cards decide the case.

Time to decide. Look back at your bet, then build your verdict from statements that hold up — no writing needed.