Myeloma and Paraproteins

Question 1

what is an antibody? and what is their function?

Answer 1

Antibody = Immunoglobulin

• Produced by B cells, mostly plasma cells
• Can be either soluble or membrane-bound (Most of them are bound to cells themselves and this is hard to measure but a significant portion is released into the blood and extracellular fluid and this is what we measure)
• Primary role is to recognise and bind pathogens
• This may directly impede the biological process or direct other components of the immune system by “tagging” the antigen

Question 2

what is the structure of an immunoglobulin?

Answer 2

• Basic structure - Y –shaped
• 2 heavy chains (Heavy chains are the longer bits)
• 2 light chains
• Variable domains -FAB (fragment antigen binding domain)
• Everything else (constant)
• Fc portion – defined by the heavy chains (as its only made up form the heavy chain as the light chain is designed to influence the variable antigen binding bit)

Question 3

what are the five different types of heavy chains?

(Leads to 5 subclasses of immunoglobulins)

Answer 3

Gamma – IgG

Alpha – IgA

Mu – IgM

Delta – IgD

Epsilon - IgE

Question 4

Heavy chains:

what is IgM?

Answer 4

Initial phase of antibody production

Exists as a pentamer – highest molecular weight

5 IgM molecules stuck together all roaming around looking for infection

Question 5

Heavy chains:

what is IgG?

Answer 5

Most prevalent antibody subclass (75% of total)

Question 6

Heavy chains:

what is IgA?

Answer 6

Mucous membrane immunity (tends to be what you find in the gut)

Question 7

Heavy chains:

what is IgE?

Answer 7

Parasite immune responses, hypersensitivity

IgE is less important in the developed world compared to the developing world

Question 8

what are the types of light chains?

Answer 8

•(Can be) Kappa or lambda

• Random selection for each cell
• But, each cell will only make 1 type of light chain with 1 specificity

Should have around half and half

• Free light chains are also found in the blood at low levels – difficult to measure

Slightly more light chains are made compared to heavy chains

Question 9

what is the Immunoglobulin structure?

Answer 9

Top bit is very diverse – ability to recognize any epitope on virus or bacterial infection

Question 10

what is Immunoglobulin production done by?

Answer 10

plasma cells

Plasma cell on left

Plasma cell main job is productizing immunoglobulin factor 8

Question 11

How can you tell which is wrong or not as lots of them and look similar at first glance

Should all be slightly different

Answer 11

All a bit different

Question 12

how do you detect the immunoglobulin?

Answer 12

Identify the immunoglobulin by the Fc portion, the subclass, and can use an assay that detects IgG heavy chain, IgA heavy chain etc

Question 13

Immunoglobulin total levels - what is the most common?

Answer 13

Can measure quantities of individual subtypes

IgG most common followed by IgA

Question 14

See a population of antibodies all the same

So how do we pick out this abnormal population

what is shown here?

Answer 14

paraproteins

Question 15

what is a paraprotein?

Answer 15

• A paraprotein – monoclonal immunoglobulin present in blood or urine
• If present, it tells us that there is monoclonal proliferation of a B lymphocyte / plasma cell somewhere in the body

A paraprotein is an abnormal protein that is produced by plasma cells in the bone marrow

(monoclonal immunoglobulin - means we have identical unique clonal population of IG somewhere)

Question 16

how do we detect paraproteins?

Answer 16

Serum protein electropheresis

(Serum = fluid part of blood that has been clotted)

Question 17

what is Serum protein electropheresis?

Answer 17

• Separates protein based on size and charge
• Forms a characteristic pattern of bands of different widths and intensities based on proteins present

Most prevalent protein in the blood is albumin and acts as a buffer

Gamma region is where immunoglobulins are

Allows us to see if there is an abnormality in the immunoglobulin composition, can see if they are all different or al the same

Picutre on front of card = This is showing normal

In contrast this is showing a one unique band

Showing paraprotein – unique population of IGs and this is how it is identified

Electrophoresis is the key test and tells you if they are all the same or different, tells us if you have a paraprotein

Question 18

Summary of tests

Answer 18

• Total immunoglobulin levels - Measures Ig subclasses by heavy chain/ Fc section
• Electrophoresis - Assesses antibody diversity, identifies paraprotein
• Immunofixation - Identifies what class of paraprotein is present (i.e. IgG, IgM) (Do Immunofixation when you have the paraprotein)
• Light chains - Assesses imbalance/ excess of light chains in urine / serum

Question 19

where do myelomas occur and what IGs are involved?

Answer 19

B cells start to encounter antigens in the germinal centre

Cancerous transformation can happen at ay point

Question 20

Immunoglobulin subclass by disease - what are they?

Answer 20

•IgM paraproteins = lymphoma

• Maturing B-lymphocytes make IgM antibody at the start of the immune response

IgM paraproteins are made by B cells as still B lymphocytes at that stage

•IgG, IgA paraproteins = myeloma

• Mature plasma cells generate these types of immunoglobulin after isotype switching

IgA and IgG are made by plasma cells

Type of paraprotein tells you a lot about the disease you are looking for

Question 21

what is a myeloma?

Answer 21

• Neoplastic disorder of plasma cells, resulting (usually) in excessive production of a single type of immunoglobulin (paraprotein)
• Clinical manifestations may result from direct effect of plasma cells, or effect of paraprotein

Question 22

who does myeloma occur in?

Answer 22

• Peaks in 7th decade (Commoner as you get older, Rare in young people)
• Ethnicity – commoner in black population than white (people don’t know why)

Question 23

what are the features of a myeloma?

Answer 23

bone disease:

• lytic bone lesions
• pathological fractures
• (spinal) cord compression
• Hypercalcaemia (relased from damaged bone as a result of lytic bone disease)

bone marrow failure esp. anaemia (growth of the plasma cells in the bone marrow results in bone marrow failure, 2nd commonest manifestation of myeloma)

Infections (increased tendency to infections due to bone marrow failure resulting in low white cells but also through the effect of the paraprotein drowning out the production of normal immunoglobulins and this is called immunoparesis)

Pictures:

Thoracic soft tissue mass, cord compression

Extensive lytic bone disease in the skull

Question 24

Myeloma - what is CRAB?

Answer 24

CRAB – hypercalcaemia, renal failure, anaemia, bone disease

CRAB are the 4 big clinical manifestations clinically

Question 25

Effects of the paraprotein: how does it cause Renal failure – cast nephropathy?

Answer 25

Immunoglobulin deposition and blockage of renal tubules

Question 26

Effects of the paraprotein: how does it cause Hyperviscosity (pretty rare)?

Answer 26

Syndrome caused by increased viscosity in blood, impaired microcirculation and hypoperfusion Commonest clinical feature is bleeding – retinal, oral, nasal, cutaneous Can also cause cardiac failure, pulmonary congestion, confusion, renal failure (quite hard to get this far)

Question 27

Effects of the paraprotein: how does it cause Hypogammaglobulinaemia?

Answer 27

Impaired production of normal Immunoglobulin Tendency to infection Hypogammaglobulinemia due to quantitively high but qualitatively you don’t have any normal IG production left

Question 28

Effects of the paraprotein: how does it cause amyloidosis? (rewatch slide 27)

Answer 28

Group of diseases characterised by deposition of fibrillar protein Morphological appearances, physical structure are similar Biochemical or protein composition can vary When caused by a paraprotein or light chains – AL amyloid - Nephrotic syndrome - Cardiac failure (LVH) - Carpal tunnel syndrome - Autonomic neuropathy - Cutaneous infiltration

Question 29

how is a Diagnosis of myeloma made?

Answer 29

•Paraproteins are common - 3-4% of population over age of 75 - The vast majority have nothing wrong with them - This is termed **monoclonal gammopathy of uncertain significance (MGUS)** * Myeloma is diagnosed by finding excess plasma cells in the bone marrow * Must comprise \> 10% of total bone marrow cell population

Question 30

Diagnosis of myeloma: how common are each types of paraproteins? and what is the stage based on?

Answer 30

- IgG 55% - IgA 21% - Light chain only 22% (Need light chain analysis to detect abnormality. All these plasma cells do is release lights chins, don’t make heavy chains so you cant see it on standard analysis as immunoglobulin subclass analysis looks for heavy chains. Light chains often missed on electrophoresis) - Other (IgD, non-secretory - Majority of non-secretory is normally a light chain myeloma) 2% •Stage - Based on albumin & beta-2 microglobulin

Question 31

what is the treatment of myeloma?

Answer 31

* Chemotherapy - Proteasome inhibitors (carfilzomib, bortezomib), IMiDs (immunomodulatory drugs) (lenalidomide, pomalidomide), monoclonal antibodies * Bisphosphonate therapy (normally used to strength bone and inhibit osteoclast activity and prevent bone breakdown. Myeloma stimulate osteoclast activity causes bone lysis and hypercalcaemia) - Zoledronic acid * Radiotherapy (good for localised symptom control) * Steroids * Surgery (if critical damage) - Pinning of long bones; decompression of spinal cord * Autologous stem cell transplant (in younger patients, upto to age of 70 if they are fit)

Question 32

what are IgM paraproteins?

Answer 32

* IgM myeloma does not exist! * IgM paraproteins are associated with low-grade lymphomas (various types) IgM production is done by B cells

Question 33

IgM paraproteins are associated with low-grade lymphomas (various types) - what is their clinical presentation?

Answer 33

Bone marrow failure (anaemia, thrombocytopenia) Lymphadenopathy Hepatosplenomegaly B symptoms (Myeloma doesn’t cause B symptoms (sweats, weight loss)) Paraprotein-related symptoms can occur Bone disease is very rare (so if you have pathological fracture, lytic lesions your not looking for IgM paraprotein)

Question 34

Answer 34

This tells us if there is a paraprotein 1. May tell you something funny is going on e.g. if it is sky high off the charts as arnt many things that cause protein to double 2. This can also let you know something is wrong 4. just measures how sticky blood is and how fast it sinks and is a measure of how much protein in the blood so will go up in patients with paraprotein/elevated proteins but not specific enough for this case

Question 35

Answer 35

2, means big globulin or thick blood, lymphoplasmic lymphoma where you have a IgM paraprotein. IgM have increased viscosity Melanoma have nothing to do with the blood

Question 36

Answer 36

Most people do require some monitoring 3. If you have any of them you don’t have MGUS and probably myeloma in that situation

Question 37

Answer 37

If you have more than 10% plasma cells then you have myeloma Not 4. as you have excess plasma cells and you don’t have lymphoma and you have a IgG paraprotein rather than a IgM paraprotein myeloma isn’t curable and doesn’t go away for most patients No point in treating if it isn’t causing harm as no point in giving chemotherapy Probably just mechanical back pain We do give bisphosphonate to protect her bones and watch her closely She doesn’t have anything to gain form treatment at this stage

Question 38

Answer 38

Developed symptomatic myeloma, got end organ damage Give more bisphosphonate Fluids for renal function Needs antimyeloma therapy