**Question:** Which of the following is the least common presentation of multiple myeloma?

A. Bone pain
B. Renal failure
C. Neurological symptoms
D. Anemia

**Core Concept:** Multiple myeloma is a plasma cell disorder characterized by the clonal proliferation of plasma cells in the bone marrow, leading to the production of monoclonal (single-type) immunoglobulins and various clinical presentations.

**Why the Correct Answer is Right:** Renal failure (option B) is the least common presentation of multiple myeloma, as it usually develops later in the disease course when plasma cell infiltration and destruction of renal tissue occur.

**Why Each Wrong Option is Incorrect:**

A. Bone pain (option A) is the most common presentation, primarily due to osteolytic lesions and skeletal complications caused by plasma cell infiltration and secretion of paraproteins.
C. Neurological symptoms (option C) can occur later in the disease course, often secondary to spinal cord compression or hypercalcemia.
D. Anemia (option D) is another common presentation due to impaired erythropoiesis caused by the presence of multiple myeloma cells and the production of monoclonal immunoglobulins that can lead to bone marrow suppression.

**Clinical Pearl:** Early recognition and diagnosis of multiple myeloma are crucial for optimal management and patient outcomes, as the disease often presents with overlapping symptoms and signs. A thorough clinical examination and appropriate investigations, including serum protein electrophoresis and imaging studies, are essential for diagnosing this disease.

**Correct Answer:** D. Anemia (option D) is the least common presentation of multiple myeloma, as it occurs later in the disease course when the primary effects of multiple myeloma cells and monoclonal immunoglobulins on bone marrow function become more pronounced.