Bayesian Causal Atlas · Vol. Multisystem · Pearl Structural Causal Model
Systemic Amyloidosis — All Types, Subtypes & Variants
Amyloidosis is a family of protein-misfolding diseases in which a precursor protein deposits as insoluble fibrils and destroys organs. The type dictates everything: AL (light-chain, a plasma-cell cancer), ATTR (transthyretin — wild-type and hereditary variant), AA (inflammatory), hereditary non-TTR (fibrinogen, apolipoprotein, gelsolin, lysozyme) and dialysis-related (β2-microglobulin). This oracle estimates the causal reduction in all-cause mortality for each type from its own evidence base, on a shared precursor→fibril→organ→death backbone. Choose a type — interventions are non-transferable and are gated accordingly. Hazard ratios are from named trials; observational, surrogate and failed-confirmatory figures are graded and flagged. For education, not individual medical advice.
Method. Structural Causal Model (SCM) with backdoor adjustment (Pearl), stratified by amyloid type. The front door is resolved through an EXPLICIT mediator cascade — precursor production → precursor stability → fibril formation → tissue burden → organ dysfunction — not a single lumped node. Each intervention is attached to the specific node it acts on, which buys three things: (i) d-separation — an upstream intervention is independent of mortality given its node, licensing a stage-wise front-door factorisation; (ii) channel saturation — interventions on the SAME node are substitutes and saturate against each other, while interventions on DIFFERENT nodes compose in series along the flux; (iii) structural cross-correlation removal — the overlap between, say, three TTR silencers falls out of their shared node rather than a hand-set ρ̄. The residual eigenvalue ρ̄ (default 0.30) now only cleans up correlation among the mediator-independent (direct) effects. Cross-type pooling is refused (positivity violation). Robustness to unmeasured confounding is quantified with the E-value. Every hazard ratio is cited.
Interventions are type-specific: choosing a type excludes non-transferable therapies from the DAG, front-door pooling, Pareto, Monte‑Carlo & sensitivity. A TTR drug does nothing for AL and vice-versa; combining across types is not causally valid.
ρ̄ = 0.30
A–D (all)
A high (RCT/meta) · B cohort · C case-series/modelled · D consensus/provisional. Lower-grade interventions are excluded from the DAG, front-door pooling, Pareto, Monte‑Carlo & sensitivity.
Interventions
Tick the interventions to combine. Each shows its trial effect estimate, 95% confidence interval (CI), E-value, mechanism, and citation. ★ = in the current Pareto effective set but not yet ticked.
Combined causal estimate
Headline is the front-door estimate: shared Amyloid overlap removed via dose-response saturation; residual direct-effect overlap removed via the eigenvalue model at ρ̄.
1.00
Combined HR
0%
Relative risk ↓
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Pooled E-value
Interventions selected (k)
0
Effective independent dimensions (n_eff)
0
Redundancy discount applied
0%
Baseline risk (illustrative anchor)
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Absolute risk after intervention
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Absolute risk difference (RD)
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Backdoor-only HR (no front-door)
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Precursor / fibril-burden overlap removed
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Number needed to treat (NNT)
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ρ-sensitivity band (ρ 0 → 0.6)
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Interpretation
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Causal attribution
Under monotonicity + exogeneity (E-value bounds the exogeneity assumption).
Probability of Necessity (PN)
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Probability of Sufficiency (PS)
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Prob. of Necessity & Sufficiency (PNS, lower bound)
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Causal DAG
Cross-correlation
Pareto (threshold)
Monte Carlo
Front-door mediation
What-if / If-not-for
Sensitivity
Antithesis
Faithful causal directed acyclic graph (DAG) with the mediator cascade drawn explicitly. Interventions attach to the node they act on: source therapies at node 1 (production) — silencers, clone eradication and source-organ transplant do so directly; stabilisers at node 2 (precursor stability); anti-fibril agents at node 3 (fibril formation). These compose in SERIES into tissue amyloid burden, which drives organ dysfunction and thence mortality (Y). Supportive therapy (SGLT2i, diuretics, anticoagulation) enters downstream at organ dysfunction. Because each stage is separated, two interventions on the same node are substitutes (they saturate) while interventions on different nodes stack in series — the graph, not a scalar, decides the overlap. The dominant back-door path is amyloid TYPE, handled by stratifying (the type selector).
Eigenvalue diagnostics for the selected interventions under an equicorrelation matrix (off-diagonal ρ̄). A large λmax relative to k signals redundancy; n_eff is the effective number of independent interventions actually contributing.
k (selected)
0
λmax
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λmin
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n_eff = (Σλ)² / Σλ²
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Condition number
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The cross-correlation is now mostly STRUCTURAL, not a single number. Interventions on the same cascade node (e.g. three TTR silencers at node 1) are near-perfect substitutes and saturate against each other within that node; interventions on different nodes (a silencer at node 1 + a stabiliser at node 2) are d-separated given the intermediate node and compose in series, so they stack — which is exactly why HELIOS-B saw real incremental benefit adding vutrisiran on a tafamidis background. The residual ρ̄ slider only governs the leftover correlation among the mediator-independent (direct) supportive effects.
Minimum-effective-set analysis. Set a target combined risk reduction; the model finds the smallest set of interventions — accounting for front-door mediator overlap — that reaches it, and highlights them. If the target exceeds what all interventions together can achieve, the full set is shown (never an empty one). "Apply" ticks exactly that set.
Target combined risk ↓ ≥ 50%
Monte Carlo propagation. Each selected intervention's log-effect is sampled from a normal distribution implied by its 95% CI; samples are combined with the same eigenvalue overlap discount. 5,000 draws.
Median combined HR
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95% simulation interval
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Standard deviation of combined HR
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P(combined HR < 0.90)
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Antithesis — challenging this oracle's own conclusions
Amyloid type is the master confounder — this graph is only valid one type at a time. “Amyloidosis” is not one disease. AL is a plasma-cell cancer; ATTR is a protein-folding disease of liver-made transthyretin; AA is a complication of chronic inflammation; hereditary non-TTR and dialysis-related forms are different again. The therapies are non-transferable and sometimes opposite: daratumumab is life-saving in AL and useless in ATTR; a TTR silencer/stabiliser is the reverse; SAA suppression is the AA answer and irrelevant to both. The type selector exists precisely because pooling interventions across types mixes populations with different baseline mortality and different mechanisms — a textbook violation of the SCM’s common-support / positivity assumption. Correct fibril typing (mass spectrometry / immunohistochemistry, not just Congo red) is the prerequisite for ANY figure here; mistyping AL as ATTR and giving a TTR drug wastes the only window to treat the clone.
Within a type, silencers + stabilisers overlap; across types, nothing adds. Inside ATTR, silencers (vutrisiran, patisiran, eplontersen) and stabilisers (tafamidis, acoramidis) converge on the same mediator (amyloid burden), so their effects are partly redundant — HELIOS-B’s incremental vutrisiran benefit on a tafamidis background is real but < additive, and the eigenvalue ρ̄ / saturation removes the double-count. The all-types view deliberately refuses to pool across types: a combined figure spanning AL + ATTR interventions is shown only as reference and flagged non-valid.
Birtamimab is the cautionary tale — a positive post-hoc that did not confirm. Birtamimab’s Mayo Stage IV post-hoc HR of 0.41 looked practice-changing; the confirmatory AFFIRM-AL trial was terminated in 2025 for missing its primary endpoint. It is retained as an anti-target: a striking sub-group signal on a stopped-for-futility trial is a hypothesis, not an effect. Read every provisional / surrogate entry (patisiran cardiac, eplontersen CM, diflunisal cardiac) through that lens.
The transplant and observational arms are selection machines. ASCT (AL), liver/kidney transplant (hereditary) and renal transplant (dialysis) are offered to the fittest, lowest-stage patients; their raw survival advantage is heavily confounded by eligibility, and advanced cardiac involvement — the main driver of death — is precisely what excludes patients from transplant. SGLT2i (0.54) and the AA/SAA survival figures are observational and healthy-user-inflated. These belong at grades B–C and their E-values are modest; a small unmeasured confounder can erode them.
Stage and lead-time dominate the numbers. Mayo Stage IV AL has a median survival measured in months; NAC/Gillmore stage I ATTR in years — the same intervention posts very different absolute benefit by stage, and disease-modifiers help most started early. Rising survival across all types partly reflects earlier diagnosis (lead-time), not only better drugs. A single combined HR blurs early and advanced disease within a type, let alone across types.
Endpoints are not uniform across the arms. ACM (vutrisiran, tafamidis, AA/SAA), composite ACM/CV-hospitalisation (acoramidis, patisiran), major-organ-deterioration PFS (daratumumab), response-conditioned survival (ASCT) and imaging surrogates are being placed on one axis. They are directionally comparable but not identical; pooling them even within a type assumes an exchangeability that the front-door decomposition only approximates.
What-if — the do-operator: P(Y | do(S))
Intervening on the selected set S with Pearl's do-operator (setting the interventions, not merely observing them). Contrast against do(∅) = no intervention.
For each intervention: "if not for this one, the combined front-door effect would be…". Isolates each intervention's marginal causal contribution after mediator-overlap removal, so shared-pathway agents are not double-credited.
If not for…
HR without it
HR with full set
marginal RRR lost
One-at-a-time sensitivity. Each intervention's effect is swung across its 95% confidence interval (others held at point estimate); the bar is the resulting swing in the combined front-door effect. A long bar means the combined estimate leans heavily on that single trial's precision.
Optimistic bound (all at CI-low)
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Point estimate
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Pessimistic bound (all at CI-high)
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Pooled E-value (confounding robustness)
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Front-door (mediation) decomposition over the explicit cascade. Each intervention’s mediated log-effect is pooled WITHIN its node with dose-response saturation (same-node substitutes), then the nodes are composed in SERIES down the flux (production → stability → fibril → burden → organ), with a series attenuation because reducing an already-reduced flux buys less. This replaces the old single-mediator global saturation: a silencer + a stabiliser no longer wrongly cancel as if competing for one pool. Direct (organ-level) effects keep the residual eigenvalue ρ̄. The per-node reductions are reported so the channel structure is visible.
Mediator saturation cap = 50% amyloid precursor / fibril-burden reduction
Sum of standalone Amyloid reduction (naive)
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Combined Amyloid reduction after saturation
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Mediator overlap removed (1 - saturation)
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Direct-effect redundancy removed (1 - n_eff/k)
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Front-door combined HR
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Backdoor-only combined HR (comparison)
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Intervention
HR
%Amy↓
med-frac
indirect log
direct log
Which % of cross-correlation is appropriate? Not one number. The mediator overlap is fixed empirically by the Amyloid saturation (currently removing — of the summed mediated effect when interventions are stacked). Note the failure modes on display: birtamimab moved a surrogate and a sub-group but its confirmatory trial failed; SGLT2i and the transplant arms move the outcome on observational, selection-confounded data. Neither should be read the way an RCT ACM result (vutrisiran, tafamidis, daratumumab) is read.
Front-door caveat (antithesis): the mediator→outcome edge is confounded by stage and organ pattern; effect sizes are stage-conditional; and the whole graph is valid only WITHIN one correctly-typed amyloidosis. The all-types view is a landscape for comparison, not a poolable model — a combined figure spanning types is shown for reference only and flagged.
Executive summary
Select interventions to generate a plain-language summary.