Monoclonal Gammopathy of Undetermined Significance (MGUS): This condition is characterized by the presence of a monoclonal protein (M protein) in the blood, which can be composed of kappa or lambda light chains. An elevated kappa light chain with a normal kappa/lambda ratio could indicate MGUS, especially if other criteria such as a low level of M protein and the absence of end-organ damage are met.

Primary Amyloidosis (AL Amyloidosis): This condition involves the deposition of amyloid fibrils composed of immunoglobulin light chains in various tissues. While the kappa/lambda ratio might be normal, an elevated level of kappa light chains could suggest AL amyloidosis, particularly if clinical symptoms such as weight loss, fatigue, and organ dysfunction are present.
Kappa Light Chain Myeloma: Although less common than lambda light chain myeloma, kappa light chain myeloma can present with an elevated level of kappa light chains. The normal kappa/lambda ratio might be seen in early stages or in cases where the lambda light chain production is also increased but to a lesser extent.
Lymphoproliferative Disorders: Certain lymphoproliferative disorders, such as lymphoma, can produce elevated levels of light chains. The kappa/lambda ratio might remain normal if both kappa and lambda-producing clones are present or if the disease is at an early stage.

Multiple Myeloma with Renal Involvement: In cases of multiple myeloma, especially those with renal involvement, the kappa/lambda ratio can be normal due to the renal excretion of light chains. Missing this diagnosis could lead to significant morbidity and mortality due to delayed treatment.
Light Chain Deposition Disease (LCDD): This rare condition involves the deposition of light chains in tissues, leading to organ dysfunction. It can present similarly to amyloidosis but with different pathological findings. Early diagnosis is crucial for management.

Heavy Chain Disease: A group of disorders characterized by the production of abnormal heavy chains, which can sometimes be associated with elevated light chain production. The kappa/lambda ratio might be normal, but clinical presentation and specific tests are needed for diagnosis.
Waldenström's Macroglobulinemia: A type of lymphoma that produces IgM monoclonal protein. While it more commonly involves lambda light chains, kappa light chain production can occur, and the kappa/lambda ratio might be normal in some cases.