Multiple myeloma is usually defined as a disease that is individual and different from the rest of cancers. It has a particular treatment and different from others. However, according to the different manifestations, certain subtypes of myeloma correspond to some features, both in terms of response to treatment in terms of complications that may suffer or experience the patients.
The different types of myeloma are based on the type of immunoglobulin (paraprotein) produced in the cell of myeloma. Each immunoglobulin has a specific structure with two major components: so heavy chains and two light chains, which are assembled in a single molecule.
There are five possible types of heavy chains, which are defined with letters G, A, D, E and M, and two types of light chains that are marked with the Greek letters Kappa (k) and Lambda (X). Each single immunoglobulin (hereinafter, Ig) can have only one of the types of heavy chains and one of the types of light chains.
In people who do not suffer from myeloma, you will find all possible combinations and are both Polyclonal immunoglobulins. In myeloma, as mentioned above, there is only a single combination of heavy and light chain, the monoclonal protein.
Basic structure of immunoglobulins
65% of patients with myeloma have an IgG type. This means type G immunoglobulin (one of the possible types of heavy chain), one combination of types of light chain, Kappa or Lambda. The second most common type is the IgA myeloma, also in combination with any of the two light chains. IgM, IgE, and IgD types have one much lower incidence. It is more common that the monoclonal paraproteins are of type Kappa to Lambda, according to the light chain.
Approximately 30% of the patients, at the same time producing a complete structure of immunoglobulin also produced light chains in excess, which are not attached to a heavy chain and that by being more “small” are eliminated in the urine. These isolated light chains are detectable in the urine and not so much in the blood. In 20% of patients, affected by myeloma cells produce only light chains and never get to produce heavy chains. The latter case is is known as light chains or Bence Jones myeloma.
In other more isolated cases, between 1 and 2% of the cases, mielomatosas cells produce little or no any immunoglobulin, which is known as nonsecretory myeloma that makes their control and diagnosis more difficult.
However, a recent development called Freelite ™ test has achieved minimal amounts of light chains in the blood in the majority of patients referred to as traditionally as non-secretory, what makes easier diagnosis and control.
There are also some differences between the behaviour of the different types of myeloma. As you can imagine, the most common myeloma or IgG is presenting symptoms commonly associated with myeloma. On the other hand, IgA myeloma can produce in some cases the formation of tumors to the bone, while the IgD type can be accompanied by plasma cell leukemia and involves more chance of damage to the kidney.
Of light chains or Bence Jones myeloma are most likely to cause damage to the kidney and deposit components of light chain in the kidneys, nervous system or other organs. Sometimes these deposits give rise to a substance called “amyloid”, resulting in a disease called amyloidosis, which consists of the deposit of this amorphous substance coming from the immunoglobulin in the tissues. It is more frequent to occur in with lambda light chain myeloma. There is also the chance of developing Amyloidosis without having multiple myeloma.