Beta-2 Microglobulin
SonstigesZuletzt geprüft: 7. April 2026. Quellenansatz: Standardkontext zur Laborinterpretation, allgemeine medizinische Referenzmaterialien sowie öffentliche Gesundheits- oder klinische Leitlinien, sofern relevant.
Was ist Beta-2 Microglobulin?
Beta-2 microglobulin (B2M) is a small protein (11.8 kDa) that forms the light chain of the major histocompatibility complex class I (MHC-I) molecule, which is expressed on the surface of virtually all nucleated cells. MHC-I molecules present intracellular peptides to CD8+ cytotoxic T cells and are essential for immune surveillance. B2M is non-covalently associated with the MHC-I heavy chain; when the MHC-I complex turns over, B2M is shed into the blood and filtered by the kidneys, where it is almost completely reabsorbed and catabolized by proximal tubular cells.
Serum B2M levels reflect the rate of cell turnover, making it a valuable tumor marker for hematologic malignancies with high cell proliferation rates—particularly multiple myeloma and lymphoma. In multiple myeloma, B2M is incorporated into the International Staging System (ISS) and Revised ISS (R-ISS) as the primary prognostic biomarker, with higher levels indicating greater tumor burden and worse prognosis. B2M is also a marker of renal function, as impaired glomerular filtration reduces B2M clearance; this dual relationship with tumor burden and kidney function must be considered when interpreting results. In chronic lymphocytic leukemia, non-Hodgkin lymphoma, and some solid tumors, B2M provides additional prognostic information.
Warum der Wert wichtig ist
B2M is one of the most important prognostic markers in multiple myeloma. The ISS stages myeloma primarily by B2M and albumin: Stage I (B2M <3.5 mg/L, albumin ≥3.5 g/dL) has a median survival of approximately 62 months, while Stage III (B2M ≥5.5 mg/L) has a median survival of approximately 29 months. Serial B2M monitoring helps track treatment response and detect relapse. Beyond myeloma, B2M is a prognostic marker in CLL, non-Hodgkin lymphoma, and Waldenstrom macroglobulinemia. Elevated urinary B2M is an early indicator of proximal tubular dysfunction (as in Fanconi syndrome, heavy metal nephrotoxicity, or antiretroviral drug toxicity), as it reflects impaired tubular reabsorption.
Normale Referenzbereiche
| Gruppe | Bereich | Einheit |
|---|---|---|
| Adults (serum) | 0.7–1.8 | mg/L |
| Adults ≥60 years (serum) | 0.7–3.0 | mg/L |
| Urine | <300 | μg/L |
Referenzbereiche können je nach Labor variieren. Vergleichen Sie Ihre Ergebnisse immer mit den Bereichen Ihres Testlabors.
Was hohe B2M-Werte bedeuten
Häufige Ursachen
- Multiple myeloma (correlates with tumor burden and stage)
- Chronic lymphocytic leukemia (CLL)
- Non-Hodgkin lymphoma
- Waldenstrom macroglobulinemia
- Chronic kidney disease (impaired clearance)
- Autoimmune diseases (SLE, rheumatoid arthritis, Sjogren's)
- Viral infections (HIV, CMV, EBV)
- Amyloidosis (AL type)
- Chronic inflammation
- Solid tumors with high cell turnover
Mögliche Symptome
- Elevated B2M itself does not produce symptoms
- In multiple myeloma: bone pain, fatigue, recurrent infections, anemia, renal insufficiency, hypercalcemia
- In lymphoma: lymphadenopathy, night sweats, unexplained weight loss, fever
- In CLL: lymphadenopathy, hepatosplenomegaly, fatigue
Was zu tun ist: Elevated B2M in the context of suspected or known hematologic malignancy requires comprehensive evaluation. For multiple myeloma, use B2M with albumin for ISS staging; add LDH and cytogenetics for R-ISS staging. Ensure renal function is assessed (creatinine, GFR), as kidney impairment independently raises B2M. For lymphoma and CLL, incorporate B2M into prognostic models. Serial monitoring tracks treatment response—declining B2M suggests effective therapy. If elevated without known malignancy, evaluate for hematologic disease, autoimmune conditions, chronic infections, and renal function.
Was niedrige B2M-Werte bedeuten
Häufige Ursachen
- Low B2M levels are uncommon and typically not clinically significant
- May be seen in some patients with early-stage or well-controlled disease
Mögliche Symptome
- Low B2M does not cause symptoms
Was zu tun ist: Low B2M is generally reassuring and requires no specific investigation. In the context of multiple myeloma or lymphoma, a low B2M is a favorable prognostic indicator. No follow-up action is needed for isolated low B2M.
Wann wird ein B2M-Test empfohlen?
- At diagnosis of multiple myeloma for staging (ISS/R-ISS)
- For serial monitoring of multiple myeloma treatment response
- As a prognostic marker in CLL and non-Hodgkin lymphoma
- When evaluating proximal tubular dysfunction (urine B2M)
- In the workup of monoclonal gammopathy of undetermined significance (MGUS) progression risk
Häufig gestellte Fragen
Verwandte Biomarker
Quellen- und Prüfungsansatz
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