In most cases, WM is preceded by a condition known as MGUS (monoclonal gammopathy of uncertain significance), and experts think this is how WM starts. This is where there is an abnormal amount of IgM detectable but people have no other symptoms and usually feel well. It may be picked up in a blood test for another unrelated condition. For most people, this has no long-term implications and they are monitored over time for any rise in IgM which may indicate WM.
WM can occur within families. Research has found that almost 1 in 5 people with WM have a relative with WM or a related blood cancer. This suggests that there may be a genetic tendency for developing WM but it does not appear to be directly inherited down the family line. Genetic screening of family members is not currently offered as the risk is still very small.
Research in the USA has found that most people with WM (90%+) have a genetic mutation called MYD88. Genetic screening at diagnosis is becoming more common in the UK including for a second WM mutation called CXXR4. These mutations may impact how people respond to new novel treatments at a molecular level.