MGUS 與冒煙型骨髓瘤

Buzzwords → Dx

Diagnostic Criteria (IMWG 2014)

• MGUS: all 3 — M-protein <3 g/dL, BMPC <10 %, no end-organ damage / SLiM event.
• Smoldering MM (SMM): M-protein ≥3 g/dL OR BMPC 10–59 %; no CRAB/SLiM.
• High-risk SMM (Mayo "20-2-20"):
  • BMPC >20 %
  • M-protein >2 g/dL
  • FLC ratio >20
  • Low / Intermediate / High = 0 / 1 / ≥2 factors.
• Active MM (out of SMM): any CRAB or SLiM event (see Multiple_Myeloma).

Workup (initial)

• CBC, BMP, Ca, albumin, LDH, β2M.
• SPE + IFE + UPE/UIFE + sFLC ratio.
• Quantitative immunoglobulins (IgG, IgA, IgM).
• Bone marrow aspirate + biopsy with FISH (only if SMM or borderline; not for low-risk MGUS).
• Whole-body low-dose CT (or PET-CT) — preferred over skeletal survey for SMM workup; MRI spine + pelvis if symptoms.
• 24-hr urine for protein quantification.
• Workup for AL amyloid if light-chain only or organ symptoms (NT-proBNP, troponin, urine albumin).

Treatment Algorithm

flowchart TD
  A[M-protein found] --> B[SPE/IFE + sFLC + 24-hr urine + IgG/A/M]
  B --> C{Meets MGUS or SMM?}
  C -- MGUS low-risk --> D[Annual FU<br>SPE + sFLC + CBC + BMP]
  C -- MGUS intermediate/high-risk --> E[6-mo then annual FU<br>+ marrow + FISH]
  C -- SMM low-risk Mayo 0 --> F[Q3-6 mo SPE + sFLC + CBC + BMP × 2 yr<br>then annual]
  C -- SMM intermediate Mayo 1 --> G[Q3-mo monitoring<br>± clinical trial]
  C -- SMM high-risk Mayo ≥2<br>or FLC ratio approaching 100 --> H[Lenalidomide ± dex E3A06<br>or KRd / Dara-len trials<br>or close monitoring with MRI/PET]
  B --> I{IgM-only MGUS?}
  I -- yes --> J[FU as MGUS but track for<br>Waldenström / lymphoma<br>+ marrow if symptoms]
  B --> K{Light-chain MGUS?}
  K -- yes --> L[Workup AL amyloid<br>NT-proBNP + troponin + urine alb<br>+ fat-pad biopsy if any organ sx]

Pearls / Pitfalls

• MGUS ≠ benign — lifetime ~1 %/yr progression risk. Risk factors (Mayo): non-IgG isotype, M-protein >1.5 g/dL, abnormal FLC ratio.
• SMM "20-2-20" predicts ~50 % 2-yr progression when ≥2 factors met. E3A06 (lenalidomide) showed PFS benefit in high-risk SMM — ASH/IMS guidelines support lenalidomide for high-risk SMM, though watching is also acceptable.²
• FLC ratio ≥100 redefines as active MM (not SMM) — even without other CRAB. Don't miss this on the FLC report.
• BMPC ≥60 % = active MM, not SMM. Picking "monitor SMM" for BMPC 65 % is wrong.
• MRI focal lesion >5 mm (≥2 lesions per IMWG) = active MM. PET-CT also acceptable; whole-body MRI superior to skeletal survey for occult lesions.
• IgM MGUS → Waldenström / LPL track, not MM. Different surveillance + treatment.
• Light-chain MGUS → screen for AL amyloid (24-hr urine, NT-proBNP, troponin, fat-pad/organ biopsy) — early AL detection saves lives (cardiac involvement is the killer).
• Non-secretory MM is rare — diagnosis hinges on bone marrow + FLC + imaging; SPE/IFE may be negative.
• No bisphosphonates for asymptomatic MGUS/SMM unless osteoporosis — they're for active MM.
• Vaccinate MGUS/SMM patients (PCV20, influenza, COVID, RZV/Shingrix); avoid live vaccines if symptomatic disease emerges.

Cross-references

• Multiple Myeloma — SLiM-CRAB transition
• AL Amyloidosis — light-chain MGUS workup
• Waldenström — IgM MGUS track
• Cytogenetics Atlas — t(11;14), t(4;14)
• Lab Values — sFLC, β2M

相關題目

• Q-061 — SMM — Mayo "20-2-20" risk stratification
• Q-062 — MGUS — distinguishing from SMM and MM
• Q-063 — Light-chain MGUS — AL amyloid screening

Sources