MM can present with many otherwise unexplained, non-specific symptoms and/or blood test abnormalities, as well as end-organ complications or related organ tissue injury.

End-organ complications that are often associated with MM include (Quach & Prince 2019):

• enhanced bone loss
• renal failure
• hypercalcaemia
• immune suppression

Signs and symptoms include (Kyle et al. 2003):

• fatigue and generalised weakness
• bone pain or pathological fracture (broken bone often with minimal trauma)
• frequent infections
• unintentional weight loss
• symptoms of hypercalcaemia including mental fogginess and/or confusion, new-onset constipation and/or abdominal pain and increased thirst
• new-onset back pain, particularly with neurological symptoms such as leg weakness, loss of bladder or bowel control, or loss of sensation
• symptoms of hyperviscosity (easy bruising, bleeding gums, cloudy vision), although this is rare. Blood test abnormalities that may suggest MM include:
• anaemia
• elevated creatinine
• hypercalcaemia
• elevated ESR in the absence of a known infection or inflammation
• an increased protein–albumin gap in the absence of infection or inflammation
• presence of a paraprotein on serum protein electrophoresis
• elevated serum kappa or lambda free light chains with abnormal kappa–lambda light chain

The presence of multiple signs and symptoms, particularly in combination with other underlying risk factors, indicates an increased risk of MM.