A 58 year old woman, who had backache and recurrent chest Infections for 6 months, develops sudden weakness of the legs and urinary retention. Her investigations show a hemoglobin of 7.3 gm/ dl, serum calcium 12.6 mg/dl, phosphate-2.5 mg/ dl, alkaline phosphatase-1OOu/l, serum albumln- 3 gm/di, globulin – 7.1 gm/dl and urea – 178 mg/d. What is the most likely diagnosis –

**Core Concept**
The patient's presentation of backache, recurrent chest infections, sudden weakness of the legs, and urinary retention, combined with laboratory findings of anemia, hypercalcemia, elevated alkaline phosphatase, and hyperglobulinemia, suggests a diagnosis of multiple myeloma, a type of plasma cell dyscrasia characterized by the proliferation of malignant plasma cells in the bone marrow.

**Why the Correct Answer is Right**
The patient's symptoms and laboratory findings are consistent with the production of a paraprotein, such as monoclonal immunoglobulin (M-protein), which leads to hypercalcemia due to bone destruction and hyperglobulinemia. The elevated alkaline phosphatase suggests bone involvement. The sudden weakness and urinary retention may be due to spinal cord compression, a common complication of multiple myeloma. The anemia is likely due to marrow infiltration by malignant plasma cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** Not applicable.
**Option C:** Not applicable.
**Option D:** Not applicable.

**Clinical Pearl / High-Yield Fact**
Multiple myeloma should be suspected in patients with backache, recurrent infections, anemia, and hypercalcemia, particularly if there is evidence of bone destruction or a paraprotein on serum protein electrophoresis.

**Correct Answer:** C. Multiple myeloma.

✓ Correct Answer: C. Multiple myeloma