Myeloma: features and investigation

Multiple myeloma (MM) is a haematological malignancy characterised by plasma cell proliferation. It arises due to genetic mutations which occur as B-lymphocytes differentiate into mature plasma cells.

Features

The median age at presentation is 70 years old.

Use the mnemonic

CRABBI:

• Calcium
  • hypercalcaemia
  • primary factor: due primarily to increased osteoclastic bone resorption caused by local cytokines (e.g. IL-1, tumour necrosis factor) released by the myeloma cells
  • much less common contributing factors: impaired renal function, increased renal tubular calcium reabsorption and elevated PTH-rP levels
  • this leads to constipation, nausea, anorexia and confusion
• Renal
  • monoclonal production of immunoglobulins results in light chain deposition within the renal tubules
  • this causes renal damage which presents as dehydration and increasing thirst
  • other causes of renal impairment in myeloma include amyloidosis, nephrocalcinosis, nephrolithiasis
• Anaemia
  • bone marrow crowding suppresses erythropoiesis leading to anaemia
  • this causes fatigue and pallor
• Bleeding
  • bone marrow crowding also results in thrombocytopenia which puts patients at increased risk of bleeding and bruising
• Bones
  • bone marrow infiltration by plasma cells and cytokine-mediated osteoclast overactivity creates lytic bone lesions
  • this may present as pain (especially in the back) and increases the risk of pathological fractures
• Infection
  • a reduction in the production of normal immunoglobulins results in increased susceptibility to infection

Other features include

• amyloidosis e.g. macroglossia
• carpal tunnel syndrome
• neuropathy
• hyperviscosity

Investigations

Bloods