Monoclonal gammopathy Undetermined significance

Related Subjects: | Hypercalcaemia | Multiple Myeloma | Extramedullary Plasmacytoma | Smouldering Myeloma | MGUS | Waldenstrom Macroglobulinaemia | Oncological emergencies

One of the key differentiating features between (MGUS) and myeloma is the absence of complications such as immune paresis, hypercalcemia and bone pain, renal disease. Monoclonal protein level < 30 g/L

About

• Monoclonal gammopathy of undetermined significance MGUS
• A paraproteinaemia (monoclonal protein) which may progress to Myeloma
• Patients have a serum Monoclonal protein < 30 g/l
• It may take up to 10 years to develop Myeloma

Epidemiology

• It is asymptomatic and extremely common
• Seen in 1% of people > 25 years, 3% > 70 years, and 10% > 80 years of age
• MGUS to Myeloma only happens in 25%

Differential of Monoclonal band

• Multiple Myeloma; Bone pain, lytic lesions, high calcium, nephropathy
• Lymphoma: Lymphadenopathy/large liver and spleen
• Chronic Lymphocytic Leukaemia (CLL) : elevated lymphocytes
• Monoclonal gammopathy Undetermined significance

Clinical

• None due to MGUS typically
• No bone pain or risk of infections
• 10-30% of patients have a demyelinating neuropathy

In MGUS there is no

• Bence-Jones proteinuria
• Lytic bone lesion
• Hypercalcaemia
• Renal insufficiency
• Anaemia
• Monoclonal Ig level > 20 g/l
• Percentage plasma cells on bone marrow examination > 4%
• Abnormal level of other Ig or immunoparesis

Risk of progression

• Overall, approximately 1% of patients with MGUS progress to myeloma each year.
• Risk factors associated with a higher chance of progressing to symptomatic disease are listed below.

Assess 3 factors

• Paraprotein level > 15 g/L +1 point
• Abnormal serum free light chain ratio +1 point
• non-IgG protein (i.e., IgA, IgE) +1 point

Number of Factors

• Risk of progression at 20 years
• No abnormal factors 5%
• 1 factor 21%
• 2 factors 37%
• 3 factors 58%

Managing a Paraprotein

Management

• Manage those at low risk of progression (i.e., = 2 factors) in general practice.
  • paraprotein level > 15 g/L 1 point
  • abnormal SFLC ratio 1 point
  • non-IgG protein (i.e., IgA, IgM) 1 point
• Review every 6 to 12 months:
• Ask about weight loss, bone pain, and night sweats.
• Check for lymphadenopathy, hepatosplenomegaly.
• Check FBC, calcium, creatinine, albumin, SPE with paraprotein levels.
• Request haematology assessment if:
  • lymphadenopathy.
  • significant rise in the level of monoclonal protein over a few months i.e., > 25% provided the absolute minimum rise is > 5 g/L.
  • new significant cytopenias (anaemia, neutropenia, thrombocytopenia).
  • high risk of progression to myeloma.
  • renal failure or development of bone pain.
  • Where appropriate, written advice may be available