Multiple myeloma is a malignant plasma cell disorder characterized by a monoclonal paraprotein, bone lesions, and excess plasma cells in the bone marrow. It has an incidence of approximately 50 cases per million population and occurs more commonly in black individuals and males. The cause is unknown but involves abnormal plasma cells secreting an immunoglobulin. Symptoms include bone pain, bone marrow failure, infections, and renal failure in some cases. Laboratory tests show anemia, elevated sedimentation rate, paraprotein, increased or abnormal free light chains, and lytic bone lesions on imaging. Related disorders include monoclonal gammopathy of undetermined significance, solitary plasmacytoma, plasma cell leukemia, and amyloidosis.

1. Multiple myeloma and plasma cell disorders
By
Ahmed Riyadh Abdul Rahman
Al-Noor University College

2. Multiple myeloma and plasma cell disorders
Multiple myeloma is a malignant disorder of plasma cells
characterized by:
1. A monoclonal paraprotein in serum and/or urine;
2. Bone changes leading to pain and pathological
fractures ;and
3. Excess plasma cells in the bone marrow (fig: 1).

3. Multiple myeloma and plasma cell disorders
Incidence
Approximately 50 cases per million population;
15%of lymphoid malignancies 2%of all malignancies;
twice as common in black than white people;
slightly more common in males than in females;
median age at diagnosis 71 years.

4. Multiple myeloma and plasma cell disorders
Aetiology and pathogenesis
The aetiology is unknown.
The cell of origin is probably a post-germinal centre B
lymphoid cell.
The cells all secrete the same immunoglobulin(Ig) or Ig
component, e.g. part of a heavy chain attached to a light
chain or light chain (κorλ).
Rarely(<1%), the cells are non-secretory.

5. Multiple myeloma and plasma cell disorders
Clinical features
• Bone pain, especially lower backache, or pathological
fracture due to skeletal involvement.
• Bone marrow failure due to marrow infiltration.
• Infection due to lack of normal immunoglobulins
(immuneparesis) and neutropenia.
• Renal failure occurs in up to one-third patients and is
caused by hypercalcaemia ,infection, deposition of
paraprotein or light chains, uric acid or amyloid.

6. Multiple myeloma and plasma cell disorders
Laboratory features
• Anaemia is frequent, often with neutropenia and
thrombocytopenia.
• Erythrocyte sedimentation rate often >100 mm/h.
• Blood film shows rouleaux with abluish back ground
staining, caused by the protein increase.
Leucoerythroblastic picture may be present.
• Bone marrow shows >10% plasma cells, often with
multinucleate and other abnormal forms.
• These cells are CD138+.

7. Laboratory features
• A paraprotein in serum and/or Bence Jones protein (light
chains) in urine with suppression of normal serum
immunoglobulins is usual.
• The paraprotein is IgG in 70%; IgA in 20%; IgM is
uncommon; IgD and IgE are rare (fig 2a and b).
• Serum light chain (either κ or λ) increased with abnormal
light chain ratio.
• Serum β2 microglobulin (β2M) often raised and higher levels
correlate with worse prognosis.
• X rays, CT scan or MRI show lytic lesions typically in skull and
axial skeleton and/or osteoporosis, often with pathological
fractures (fig 3).

8. Laboratory features
• A paraprotein in serum and/or Bence Jones protein (light
chains) in urine with suppression of normal serum
immunoglobulins is usual.
• The paraprotein is IgG in 70%; IgA in 20%; IgM is
uncommon; IgD and IgE are rare (fig 2a and b).
• Serum light chain (either κ or λ) increased with abnormal
light chain ratio.
• Serum β2 microglobulin (β2M) often raised and higher levels
correlate with worse prognosis.
• X rays, CT scan or MRI show lytic lesions typically in skull and
axial skeleton and/or osteoporosis, often with pathological
fractures (fig 3).

9. Related disorders
Monoclonal gammopathy of undetermined significance;
 MGUS is an indolent disorder more common than
myeloma and characterized by a low (< 30 g/L) and
stationary serum level of paraprotein,
 no reduction in normal immunoglobulins, no or mild
increase in one or other light chain,
 absence of skeletal abnormalities and of Bence Jones
protein and
 less than10% plasma cells in the marrow
 It may progress slowly to myeloma in approximately1%of
patients per year of follow-up.
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10. Related disorders
- Solitary plasmacytoma may occur in bone or in soft
tissues, a low level of serum paraprotein may occur and
some cases later develop myeloma.
- Plasma cell leukaemia is an aggressive disorder in which
large numbers of plasma cells circulate.The prognosis is
poor.
- Amyloidosis may cause macroglossia,
hepatosplenomegaly ,cardiac or renal failure.
Amyloid derived from clonal lymphocyte or plasma cell
proliferation (AL) (e.g.myeloma, primary amyloidosis)
when immunoglobulin light chains or components of them
are deposited. Amyeloid is stains with Congo red.