What is the SINGLE most likely biochemical abnormality associated with multiple myeloma?

Multiple myeloma is characterized by the proliferation of malignant plasma cells within the bone marrow, which can lead to a range of biochemical abnormalities as the disease progresses. Among these, hypercalcaemia is the single most likely abnormality observed in patients with multiple myeloma. This condition arises primarily due to increased osteoclast activity, promoted by osteolytic lesions caused by the myeloma cells. The release of osteoclastic factors leads to increased resorption of bone, resulting in elevated levels of calcium in the bloodstream.

The presence of osteolytic bone lesions is a hallmark of multiple myeloma, and the associated bone destruction significantly contributes to the development of hypercalcaemia. Patients often present with symptoms related to high calcium levels, such as fatigue, weakness, nausea, and confusion.

In contrast, the other biochemical abnormalities listed—hyperkalaemia, hypernatraemia, and hypocalcaemia—are not commonly associated with multiple myeloma. Hyperkalaemia may occur due to renal impairment but is not a direct consequence of myeloma. Hypernatraemia can result from dehydration or certain treatments but is also not characteristic of the disease. Hypocalcaemia is typically linked to other conditions, such