Myeloproliferative neoplasms (MPNs) are a group of blood cancers that affect around 3 per 100,000 people in the UK. Patients often experience life limiting symptoms and treatments vary depending on the type of MPN, genetic mutations present and severity of disease. There is little information on the causes of myeloproliferative neoplasms (MPNs). Patients often ask why do I have this disease? and for the majority there is no obvious reason. The aim of the MOSAICC Study is to identify factors that may cause MPNs in order to identify ways to prevent it.