Multiple Myeloma in Singapore: Symptoms (CRAB) & Treatment

Written & reviewed by the BestDoctors.sg editorial team · Last updated 23 Aug 2026 · General information, not medical advice

The honest, hopeful message: myeloma is a long-term condition to live with rather than a quick fix – but treatment has advanced greatly, and many people have long periods of good-quality remission.

What multiple myeloma is

Plasma cells are white blood cells in the bone marrow whose job is to make antibodies that fight infection. In myeloma, one plasma cell becomes abnormal and multiplies out of control, producing many identical copies. These crowd the marrow (reducing normal red cells, white cells and platelets) and pump out a single abnormal antibody protein – the paraprotein or M-protein – which can clog the kidneys and, together with signals that break down bone, cause much of the damage. It is called “multiple” because it usually affects several areas of marrow at once.

How it differs from leukaemia and lymphoma

All three are blood cancers, but they’re distinct. Leukaemia mainly involves the marrow and bloodstream overproducing abnormal white blood cells. Lymphoma starts in the lymphatic system. Myeloma starts specifically in plasma cells in the bone marrow and is defined by the abnormal protein it produces and the bone and kidney damage that follows.

Symptoms – the CRAB pattern (and others)

Early myeloma may cause few or no symptoms. When symptoms appear, they often follow the CRAB pattern:

• C – high Calcium: thirst, frequent urination, nausea, constipation, confusion, muscle weakness;
• R – Renal (kidney) impairment: the abnormal protein can damage the kidneys, sometimes causing leg swelling or a change found on blood tests;
• A – Anaemia: low red cells causing tiredness, breathlessness, dizziness or pallor;
• B – Bone problems: bone pain (classically in the back and rib cage), thinning bones and fractures with little or no injury.

Other common features include persistent fatigue and recurrent or slow-to-clear infections. These symptoms are common and usually caused by something far less serious – but if they’re persistent and unexplained, they’re worth checking.

Who gets it and what raises the risk

Myeloma is mainly a disease of older adults, with risk increasing with age (most people are diagnosed from around the mid-50s onward), and it’s a little more common in men. Recognised risk factors include a personal history of MGUS (see below) and a family history. For most people no single clear cause is identified.

How it’s diagnosed

• Blood tests – to detect the abnormal paraprotein/M-protein, plus a full blood count, calcium and kidney function;
• Urine tests – to look for myeloma protein passed into the urine;
• Imaging – X-rays, CT, MRI or PET to look for bone damage;
• Bone-marrow biopsy – usually from the back of the hip bone, to confirm the abnormal plasma cells and guide treatment.

The earlier stages: MGUS and smouldering myeloma

Many people have an abnormal protein without having myeloma. MGUS (monoclonal gammopathy of undetermined significance) is a common, benign precursor with no organ damage; only a minority of people with MGUS ever progress to myeloma, so it’s usually just monitored with periodic blood tests. Smouldering myeloma is a further stage with more abnormal cells or protein but still no CRAB-type damage; it carries a higher chance of progressing and is monitored closely, with treatment sometimes considered for higher-risk cases.

Treatment and outlook

Myeloma is usually not curable but very treatable, and outcomes have improved substantially. Treatment typically combines anti-myeloma drug combinations (including targeted therapies and immunotherapies, often with steroids), a stem-cell transplant in suitable fitter patients, and supportive care to protect the bones, support the kidneys, treat anaemia, manage pain and prevent infections. Treatment often works in phases – intensive initial treatment to bring the disease under control, then maintenance. Many people have periods of remission; if the disease returns, further lines of treatment are available.

When to see a doctor

See a doctor for persistent, unexplained bone or back pain, frequent or hard-to-shake infections, ongoing unusual tiredness or breathlessness, or symptoms of high calcium (marked thirst, confusion, constipation). These symptoms are common and usually not cancer – but persistent, unexplained ones deserve assessment, often starting with simple blood and urine tests. Seek urgent care for a bone that breaks after minimal injury or sudden severe back pain with weakness or numbness. A haematologist leads diagnosis and treatment.

Related blood & haematology topics

• Anaemia
• Iron-deficiency anaemia
• Vitamin B12 & folate deficiency
• Thalassaemia
• G6PD deficiency
• Deep vein thrombosis (DVT)
• Low platelets (thrombocytopenia)
• Haemophilia
• Understanding your full blood count
• Pulmonary embolism
• Haematologists in Singapore
• Bone Cancer
• Amyloidosis

Sources

• HealthHub Singapore — Multiple myeloma: SG patient page; definition, CRAB symptoms, risk factors and diagnosis.
• SingHealth — Multiple myeloma: SG tertiary-care overview of symptoms and treatment.
• NHS — Multiple myeloma: symptoms, diagnosis and the “treatable but usually not curable” framing.
• Mayo Clinic / International Myeloma Foundation — CRAB and IMWG diagnostic criteria, MGUS and smouldering myeloma.