A 55-year-old diabetic Raj from Mumbai has a long history of renal failure. He is currently waiting for an organ for transplant and has been on hemodialysis in the interim. If this man develops amyloid deposits around his joints, they are likely to be composed of which of the following substances?
**Core Concept:** Amyloidosis is a group of diseases characterized by extracellular deposition of insoluble protein fibers in tissues and organs, leading to organ dysfunction and dysfunctional proteins. In diabetes, amyloid deposits are commonly seen in the heart, gastrointestinal tract, and joints.
**Why the Correct Answer is Right:** In this case, the patient is a 55-year-old diabetic Raj from Mumbai with a long history of renal failure. He is on hemodialysis, which worsens amyloid deposition due to prolonged circulation of dysfunctional proteins in the blood. Among the options, option D (Albumin) is most likely to form amyloid deposits in the context of this scenario. Albumin is a protein produced in the liver, which is filtered through the kidneys and lost in patients with renal failure. In the context of hemodialysis, the loss of albumin is even more pronounced, leading to its increased presence in the circulation.
**Why Each Wrong Option is Incorrect:**
A. Beta-2-microglobulin (B2M): This option is incorrect because B2M is a 11,000-Da protein and is not prone to form amyloid deposits like larger proteins.
B. Immunoglobulins: This option is incorrect because amyloidosis due to immunoglobulins is less common, and the patient does not have a primary immunoglobulin disorder.
C. Transferrin: This option is incorrect because transferrin is a 76 kDa iron-binding glycoprotein, which is not prone to form amyloid deposits like larger proteins.
**Clinical Pearl:** In patients on hemodialysis, amyloidosis due to hemodialysis-related amyloidosis needs to be considered. This form of amyloidosis is caused by the deposition of preformed protein fibrils in tissues and organs due to prolonged exposure of proteins to circulation.
**Correct Answer:** D. Albumin
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In the context of this scenario, the correct answer is D. Albumin, as it is a large protein (~66 kDa) and is prone to form amyloid deposits in patients with renal failure undergoing hemodialysis due to prolonged exposure of proteins to circulation. The other options are incorrect because they represent proteins of different molecular weights or are not prone to form amyloid deposits in this clinical context. Amyloidosis due to hemodialysis-related amyloidosis should be considered in patients with renal failure undergoing hemodialysis, as it is a common complication in these patients.