Deposition of protein ‘A b 2m’ is seen in which clinicopathologic category of amyloidosis-
**Core Concept:** Amyloidosis is a group of disorders characterized by the extracellular deposition of fibrillar proteins, leading to organ dysfunction and failure. The primary amyloid protein can be different in various forms of amyloidosis.
**Why the Correct Answer is Right:** Amyloidosis is classified based on the type of amyloid protein involved. In this case, the protein 'A beta 2m' is involved, which is derived from the beta 2-microglobulin protein. This protein is a component of the major histocompatibility complex class I molecules and is normally cleared from the blood by the kidneys. In cases of renal dysfunction, such as renal amyloidosis, the beta 2m protein is not cleared efficiently, resulting in its deposition in various organs and tissues.
**Why Each Wrong Option is Incorrect:**
A. Amyloid A (AA) amyloidosis primarily involves amyloid A protein, derived from acute-phase reactants in response to inflammation. This is different from the correct answer.
B. Amyloid P (AP) amyloidosis is characterized by the deposition of amyloid P protein, which is unrelated to the given amyloid protein.
C. AL amyloidosis is caused by monoclonal light chain deposition, usually from plasma cell dyscrasias, not related to the given protein 'A beta 2m'.
D. Cardiac amyloidosis involves deposition of various amyloid proteins, but the specific protein 'A beta 2m' is not one of the common involved proteins in this form of amyloidosis.
**Clinical Pearl:** In clinical practice, recognizing the specific amyloid protein involved is crucial for selecting appropriate treatment strategies. For example, the use of dialysis can potentially prevent renal amyloidosis (option A) and cardiac amyloidosis (option D), but not renal amyloidosis due to 'A beta 2m' (option C) or AL amyloidosis (option C).
**Correct Answer:** D. Cardiac amyloidosis. Amyloid protein 'A beta 2m' is predominantly involved in renal amyloidosis (option C), not cardiac amyloidosis.