**Core Concept**
Plasmapheresis is a medical treatment that involves the separation of plasma from blood cells, with the removal of the plasma and replacement with a substitute solution or the patient's own plasma. This process is used to treat various conditions characterized by abnormal proteins or antibodies in the plasma.

**Why the Correct Answer is Right**
The treatment of choice for conditions like Guillain-Barré syndrome (GBS), myasthenia gravis, and certain autoimmune disorders is plasmapheresis. In these conditions, abnormal antibodies are present in the plasma that attack the body's own tissues, leading to inflammation and tissue damage. Plasmapheresis helps to remove these antibodies from the circulation, thereby reducing the severity of the condition. The process also helps to reduce the levels of inflammatory mediators and other harmful substances that contribute to the disease process.

**Why Each Wrong Option is Incorrect**
**Option A:** While dialysis is a treatment for renal failure, it is not the primary indication for plasmapheresis.
**Option B:** Transfusion of blood products may be necessary in certain cases, but it is not a substitute for plasmapheresis.
**Option C:** Corticosteroids are used to reduce inflammation, but they do not directly address the removal of abnormal antibodies from the plasma.

**Clinical Pearl / High-Yield Fact**
Plasmapheresis is often used in conjunction with immunosuppressive medications to enhance its effectiveness in treating autoimmune disorders.

**Correct Answer:** C. Thrombotic thrombocytopenic purpura (TTP).