Define Multiple Myeloma. Describe its clinical features, investigations and management.

Definition

Multiple myeloma is a malignant proliferation of plasma cells in the bone marrow producing a monoclonal immunoglobulin (paraprotein). Although a haematological malignancy, it is the commonest primary malignant tumour of bone and a key differential for destructive bone lesions in the older adult (typically > 60 years).

Clinical Features

Remembered by ‘crab’: hyperCalcaemia, Renal impairment, Anaemia and Bone lesions/Back pain. Patients present with bone pain (especially the spine), pathological fractures, fatigue from anaemia, recurrent infections and features of hypercalcaemia or renal failure.

Investigations

Blood/urine: monoclonal paraprotein on serum electrophoresis, Bence-Jones protein in urine, raised ESR, anaemia, hypercalcaemia, renal impairment and rouleaux on the film. Imaging classically shows multiple ‘punched-out’ lytic lesions (and diffuse osteopenia); note that the radionuclide bone scan is often negative because the lesions are purely lytic with little osteoblastic activity — a whole-body MRI/low-dose CT or skeletal survey is preferred. Bone-marrow biopsy confirms the plasma-cell infiltrate.

Management

Management is by haemato-oncology with systemic chemotherapy/novel agents (proteasome inhibitors, immunomodulators ± autologous stem-cell transplant), bisphosphonates for skeletal protection and hypercalcaemia, and supportive care. The orthopaedic role is stabilisation of pathological or impending fractures and radiotherapy/decompression for spinal cord compression.

Solitary Plasmacytoma

A single focus of malignant plasma cells in bone is a solitary plasmacytoma; it often presents with a destructive lytic lesion or a pathological (frequently vertebral) fracture and is treated with radiotherapy, but a large proportion progress to multiple myeloma over subsequent years, so continued haematological follow-up is required.

Bone scan is falsely negative — use skeletal survey.

• Malignant plasma-cell proliferation; commonest primary bone malignancy; older adults.
• Crab: hyperCalcaemia, Renal impairment, Anaemia, Bone lesions/back pain.
• Paraprotein + Bence-Jones protein; ‘punched-out’ lytic lesions; bone scan often negative.
• Haemato-oncology treatment + bisphosphonates; orthopaedics stabilises fractures / treats cord compression.