Free light chain

Free Light Chain
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Overview

Free light chains (FLCs) are immunoglobulin light chains that are not bound to heavy chains. They are produced by plasma cells and are present in the blood. FLCs are important in the diagnosis and monitoring of various plasma cell dyscrasias, such as multiple myeloma and light chain amyloidosis.

Structure and Function

Immunoglobulins, or antibodies, are composed of two types of polypeptide chains: heavy chains and light chains. Light chains are of two types: kappa (κ) and lambda (λ). Each immunoglobulin molecule contains two identical light chains and two identical heavy chains. Free light chains are those light chains that are not attached to heavy chains.

Kappa and Lambda Light Chains

The ratio of kappa to lambda light chains in the blood is an important diagnostic marker. Normally, the kappa to lambda ratio is approximately 0.26 to 1.65. An abnormal ratio can indicate the presence of a monoclonal gammopathy.

Clinical Significance

Free light chains are clinically significant in the diagnosis and monitoring of several conditions:

Multiple Myeloma

In multiple myeloma, a type of cancer that affects plasma cells, there is often an overproduction of a single type of light chain. This can lead to an abnormal kappa to lambda ratio. Measurement of serum free light chains is used to monitor disease progression and response to treatment.

Light Chain Amyloidosis

In light chain amyloidosis, misfolded light chains deposit in tissues, leading to organ dysfunction. The measurement of free light chains can aid in the diagnosis and monitoring of this condition.

Monoclonal Gammopathy of Undetermined Significance (MGUS)

MGUS is a condition where there is a presence of a monoclonal protein in the blood without the symptoms of multiple myeloma or other related diseases. Monitoring free light chains can help in assessing the risk of progression to multiple myeloma.

Diagnostic Testing

The serum free light chain assay is a sensitive test used to measure the concentration of free kappa and lambda light chains in the blood. This test is often used in conjunction with other tests such as serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE).

Interpretation of Results

- Normal Range: The normal range for kappa free light chains is 3.3 to 19.4 mg/L, and for lambda free light chains, it is 5.7 to 26.3 mg/L. - Kappa/Lambda Ratio: A normal kappa/lambda ratio is between 0.26 and 1.65. Ratios outside this range may indicate a monoclonal gammopathy.

Pathophysiology

The overproduction of free light chains in plasma cell disorders is due to the clonal proliferation of plasma cells that produce a single type of light chain. These excess light chains can accumulate in the blood and tissues, leading to various clinical manifestations.

Treatment and Management

The management of conditions associated with abnormal free light chains depends on the underlying disease. In multiple myeloma, treatment may include chemotherapy, immunotherapy, and stem cell transplantation. In light chain amyloidosis, treatment focuses on reducing the production of the amyloidogenic light chains.

See Also

• Immunoglobulin
• Plasma cell
• Monoclonal gammopathy
• Serum protein electrophoresis

External Links

• [International Myeloma Foundation](https://www.myeloma.org)
• [Amyloidosis Foundation](https://www.amyloidosis.org)

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