Occasionally, there occurs in a normal bone containing normal active bone marrow, a malignant clone of plasma cells that grows as a single tumour and causes bone destruction such that the patient comes to clinical attention with bone pain; an x-ray at this time shows destruction within the bone; on further staging (vide infra) there is no sign of any other disease elsewhere in the body. Such a single bone lesion is known as a solitary plasmacytoma and is treated as such - viz.a solitary tumour – see below.
However, there is no doubt that such single clones of malignant cells/plasmacytomata often seed off cells - qnd this frequently occurs early in the natural history; these take hold and grow in the other bones of the body and permeate the marrow - then the disease is called multiple myeloma. Multiple myeloma is more frequently encountered than single plasmacytoma in clinical practice.
Exposure to ionising radiation predisposes to myeloma and the Japanese nuclear weapon survivors have an increased incidence of this disease, as did the early generations of radiologists. Other predisposing causes are not well established.
