A 58-year-old Indian man presents with bone pain, fatigue, and recurrent infections. Investigations show serum creatinine 3.2 mg/dL, serum calcium 12.5 mg/dL, hemoglobin 8.5 g/dL, and bone marrow showing 65% clonal plasma cells. Which of the following complications is NOT typically associated with multiple myeloma?

Question

Accepted Answer

A. Acute leukemoid reaction with marked elevation of white blood cell count (>50,000/μL) as a direct effect of myeloma cell proliferation. ## Complications of Multiple Myeloma

**Key Point:** Multiple myeloma is associated with multiple serious complications, but acute leukemoid reaction is NOT a typical feature. A leukemoid reaction (marked WBC elevation in response to infection, inflammation, or malignancy) can occur in myeloma patients, but it is a secondary response to infection or stress, not a direct effect of myeloma cell proliferation.

### Typical Complications of Multiple Myeloma

| Complication | Mechanism | Frequency |
| --- | --- | --- |
| Light-chain nephropathy | Direct tubular toxicity of free light chains; cast formation in distal tubules | Very common (50%) |
| Hyperviscosity syndrome | High concentration of monoclonal immunoglobulin (especially IgM, IgA) | 5–10% (more common in Waldenström) |
| Tumor lysis syndrome | Rapid cell death releases intracellular contents (K⁺, phosphate, uric acid) | Uncommon spontaneously; common post-chemo |
| Infections | Suppressed normal immunoglobulin production; impaired cell-mediated immunity | Very common |
| Hypercalcemia | Osteoclastic bone resorption; impaired renal excretion | 20–30% |
| Leukemoid reaction | Secondary to infection or inflammatory response, NOT direct myeloma effect | Uncommon and secondary |

**High-Yield:** Tumor lysis syndrome CAN occur spontaneously in myeloma (especially with high tumor burden) and is a medical emergency. However, acute leukemoid reaction (WBC >50,000/μL) is NOT a direct manifestation of myeloma itself — it occurs only as a secondary response to infection or chemotherapy toxicity.

**Clinical Pearl:** In a myeloma patient with WBC >50,000/μL, always search for an underlying infection (pneumonia, urinary tract infection) or other trigger. A true leukemoid reaction is not a primary complication of myeloma.

**Warning:** Do not confuse leukemoid reaction (benign, reactive WBC elevation) with leukemic transformation (rare but serious complication of myeloma). Leukemic transformation is a true complication; leukemoid reaction is not.

### Why Option 3 is Correct

Acute leukemoid reaction with WBC >50,000/μL is NOT a direct complication of myeloma cell proliferation. While myeloma patients can develop leukemoid reactions in response to infection or stress, this is a secondary phenomenon, not a primary manifestation of the disease. The other three options (light-chain nephropathy, hyperviscosity syndrome, and tumor lysis syndrome) are well-established, direct complications of myeloma.

Answer

B. Hyperviscosity syndrome due to high serum monoclonal protein concentration causing neurological and visual symptoms

Answer

C. Light-chain cast nephropathy (myeloma kidney) leading to acute kidney injury and progressive renal dysfunction

Answer

D. Tumor lysis syndrome with hyperkalemia, hyperphosphatemia, and hyperuricemia occurring spontaneously or after chemotherapy initiation

Explanation

Complications of Multiple Myeloma

Typical Complications of Multiple Myeloma

Why Option 3 is Correct

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Complication	Mechanism	Frequency
Light-chain nephropathy	Direct tubular toxicity of free light chains; cast formation in distal tubules	Very common (50%)
Hyperviscosity syndrome	High concentration of monoclonal immunoglobulin (especially IgM, IgA)	5–10% (more common in Waldenström)
Tumor lysis syndrome	Rapid cell death releases intracellular contents (K⁺, phosphate, uric acid)	Uncommon spontaneously; common post-chemo
Infections	Suppressed normal immunoglobulin production; impaired cell-mediated immunity	Very common
Hypercalcemia	Osteoclastic bone resorption; impaired renal excretion	20–30%
Leukemoid reaction	Secondary to infection or inflammatory response, NOT direct myeloma effect	Uncommon and secondary