What Is A Paraprotein Level In Multiple Myeloma?

Paraprotein is an important marker for the presence of various diseases, some of which are malignant while others are a non-malignant systemic disease. Paraprotein is a monoclonal immunoglobin secreted by the abnormal plasma cells. Multiple myeloma is the cancer of plasma cells and these malignant cells secrete a considerable quantity of paraprotein which helps in the diagnosis of the disease.⁽¹⁾

Presence of paraprotein in the blood and urine and its level is a crucial marker for the presence of multiple myeloma. However, there is multiple myeloma which is not characterized by the increased level of paraprotein. These are known as non-secretory myeloma, less common and difficult to diagnose. The level of paraprotein also indicates the stage of the disease. If the level of paraprotein is significantly high, it can be concluded that the disease is in the advanced stage. If the paraprotein level is above 30 g/l without any other serious symptoms, the condition is termed as Smouldering myeloma which is an intermediate stage of progression of multiple myeloma.

According to the International myeloma working group, level of paraprotein above 30 g/l along with end-organ damage characterized by renal failure, bone lesions, and anemia is the diagnosis of multiple myeloma.

Paraprotein is secreted by the mature B cells characterized by the clonal population of B cells. Paraprotein is present in the blood and urine samples of the patient and is a monoclonal immunoglobulin. The various diseases are diagnosed due to the presence of paraprotein with altered levels. In some disease, the value of paraprotein increases while in some cases the value significantly increases; although, the most common marker in case of multiple myeloma, the level of paraprotein may be increased in various diseases. The testing of paraprotein or M-protein is done when the other physical, as well as diagnostic parameters, indicate the presence of multiple myeloma or other diseases.

Various diseases which may result in the increases in paraprotein levels are:

Malignant B-Cell Disorders:

Generally, the paraprotein is secreted by the malignant B cells, which are generally the plasma cells. Following are the various disorders related to malignant B-cells which lead to increase in paraprotein levels:

• Multiple Myeloma- The multiple myeloma is the excessive production of the malignant plasma cells. The condition includes symptomatic and asymptomatic myeloma, non-secretory myeloma and leukemia.
• Crow–Fukase Syndrome- This condition also has an altered level of paraprotein. The symptoms of this syndrome include polyneuropathy, organomegaly, endocrinopathy, myeloma protein, and skin changes.
• Lymphoproliferative Disorders- Various lymphoproliferative disorders such as Non‐Hodgkin lymphomas and chronic lymphocytic leukemia increases the level of paraprotein in blood and urine.
• Plasmacytoma- It is the condition characterized by plasma cell dyscrasia. The condition is divided into solitary plasmacytoma of bone (SPB), extramedullary plasmacytoma (EP), and multiple plasmacytomas. SPB and EP may lead to an increased level of paraprotein.
• Amyloidosis– Amyloid light-chain (AL) amyloidosis or primary amyloidosis has increased the level of paraprotein which may accumulate into vital organs such as kidney and heart.

Non‐Malignant Disease

Apart from the malignant diseases, various other diseases also alter the level of paraprotein in blood and urine:

Skin And Soft Tissue Disease- Diseases such as Necrobiotic xanthogranulomatosis and Pyoderma gangrenosum increases the level of paraprotein.

Autoimmune Disease- These are the diseases in which the immune system of the body starts damaging its own tissues and organs. Paraprotein levels are increased in conditions such as Rheumatoid arthritis.

Hepatic Disorders- Paraprotein levels are increased in hepatitis and liver cirrhosis.

Presence of paraprotein in the blood as well urine indicates the presence of various diseases, some of which are serious and fatal. The disease may be malignant such as multiple myeloma or lymphoproliferative disorder or may be non-malignant such as rheumatoid arthritis or hepatitis. Paraprotein level more than 30 g/l along with the other serious symptoms such as hypercalcemia, renal failure, and bone lesions indicates the presence of multiple myeloma.

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