Page 287 - Essential Haematology

Chapter 21 Multiple myeloma and related disorders / 273

Paraproteinaemia (MGUS; see below). Other plasma cell neoplasms
are listed in Table 21.2 .
This is the presence of a monoclonal immunoglobu-

The myeloma cell is a post - germinal centre

lin band in the serum. Normally, serum immuno-
plasma cell that has undergone immunoglobulin
globulins are polyclonal and represent the combined
class switching and somatic hypermutation and

output from millions of different plasma cells. A
secretes the paraprotein that is present in serum.
monoclonal band (M - protein), or paraprotein ,
Immunoglobulin heavy and light chain genes are

reflects the synthesis of immunoglobulin from a
clonally rearranged. Plasma cells naturally home to
single clone of plasma cells. This may occur as a

the bone marrow and this characteristic is retained
primary neoplastic disease or secondary to an

by the tumour cell. The aetiology of the disease is
underlying benign or neoplastic disease aff ecting
unknown but it is more common in certain racial
the immune system (Table 21.1 ).
groups such as black individuals. Tumour cells accu-
mulate complex genetic changes but dysregulated
Multiple m yeloma or increased expression of cyclin D (see p. 278 ) is

believed to be an early unifying event.
Multiple myeloma (myelomatosis) is a neoplastic
disease characterized by plasma cell accumulation

in the bone marrow, the presence of monoclonal Diagnosis
protein in the serum and/or urine and, in sympto-
Symptomatic myeloma is diagnosed if there is:
matic patients, related tissue damage. Ninety -
eight per cent of cases occur over the age of 40 years 1 Monoclonal protein in serum and/or urine
with a peak incidence in the seventh decade. (Fig. 21.1 )
The term asymptomatic (smouldering) multiple 2 Increased clonal plasma cells in the bone marrow

myeloma is used for cases with similar laboratory (Fig. 21.2 ) and
findings but no organ or tissue damage. Retrospective 3 Related organ or tissue impairment.

analysis of serum samples has shown that almost all
A useful acronym for tissue damage is CRAB
cases of myeloma develop from a pre - existing mono-
(hypercalaemia, renal impairment, anaemia, bone
clonal gammopathy of undetermined signifi cance
Table 21.2 Plasma cell neoplasms (WHO,

Table 21.1 Diseases associated with 2008).
monoclonal immunoglobulins.
Monoclonal gammopathy of undetermined
Neoplastic signifi cance (MGUS)
Multiple myeloma
Plasma cell myeloma
Solitary plasmacytoma
Variants:
Monoclonal gammopathy of undetermined
Asymptomatic (smouldering) myeloma
signifi cance (MGUS)
Non - secretory myeloma
Waldenstr ö m macroglobulinaemia
Plasma cell leukaemia
Non - Hodgkin lymphoma
Chronic lymphocytic leukaemia Plasmacytoma
Primary amyloidosis Solitary plasmacytoma of bone
Heavy - chain disease Extraosseous (extramedullary) plasmacytoma
Immunoglobulin deposition diseases
Benign
Primary amyloidosis
Chronic cold haemagglutinin disease
Systemic light and heavy chain deposition
Transient (e.g. with infections)
diseases
HIV infection
Gaucher ’ s disease Osteosclerotic myeloma (POEMS syndrome)