**Question:** A 50 year old female patient complains of weakness and pain in back. Patient gives history of recurrent infections. Lab investigation reveals presence of Bence Jones proteins in urine. This condition results in the overproduction of abnormal immunoglobulins which are mostly?

A. Light chains
B. IgA
C. IgD
D. IgE

**Correct Answer:** D. IgE

**Core Concept:**
Bence Jones proteins are light chains (monoclonal light chains) produced by plasma cells in multiple myeloma or other plasma cell dyscrasias. These proteins are usually not detected in normal urine, but their presence indicates the overproduction of abnormal immunoglobulins.

**Why the Correct Answer is Right:**
In this case, the correct answer is D. IgE (Immunoglobulin E) because IgE is a subclass of immunoglobulins (Ig) produced in response to allergens. In the context of the patient's history of recurrent infections and the presence of Bence Jones proteins in urine, it is unlikely that the overproduction of abnormal immunoglobulins is due to IgE.

**Why Each Wrong Option is Incorrect:**
A. Light chains are the actual abnormal immunoglobulins overproduced, not the type of immunoglobulin (Ig). So option A is incorrect.
B. IgA (IgA) is a common type of immunoglobulin, but in this case, the overproduction is more likely due to light chains, not IgA. So option B is incorrect.
C. IgD is a rare immunoglobulin type, and its overproduction is not the main cause of Bence Jones proteins in urine. Therefore, option C is incorrect.
D. IgE, as explained above, is the correct answer, but it is more likely to cause allergic reactions rather than recurrent infections. IgE-related disease is less relevant in this context, making option D incorrect.

**Clinical Pearl:**
A better understanding of the patient's history and clinical context is essential to differentiate between the various types of immunoglobulins and their clinical implications. In this case, the presence of Bence Jones proteins in urine indicates the overproduction of light chains, which is more likely due to multiple myeloma or other plasma cell dyscrasias. These conditions are associated with recurrent infections rather than allergic reactions.