Answer :USMLE step 2 Mcq 295:A 68 year old man is hospitalised because of recent general deterioration and weight loss




Correct Answer: E

The correct answer is e) multiple myeloma  . In hospitalized patients, malignancy rather than hyperparathyroidism is the most common cause of hypercalcemia; and, generally, patients can be divided into two groups: (1) those with hematologic malignancies (25%) and (2) those with solid tumors Patients in the hematologic malignancy group include those with multiple myeloma, those with some lymphomas or leukemias, and a subset of breast cancer patients. These patients have lytic bone metastases and histologically demonstrate increased osteoclast bone resorption adjacent to tumor cells. The cause of the hypercalcemia in these patients is local cytokine release (mainly interleukin-1beta and tumor necrosis factor-beta) stimulating osteoclasts to resorb bone. These patients have elevated serum levels of calcium and phosphate and low urine levels of cyclic AMP Hypercalcemia is one of the most common of metabolic disorders. Although there are many causes of hypercalcemia, primary hyperparathyroidism (PH) and malignancy account for the majority of the cases. In the clinic, hyperparathyroidism is likely to be the cause, while malignancy is the likely cause in the hospital. The hypercalcemia of malignancy can occur with or without bone metastases. In both circumstances, the production by the tumor of parathyroid hormone-related protein (PTHrP) is the most common cause of the increased osteoclastic bone resorption that causes the hypercalcemia. Hypercalcemia can occur through one or a combination of three mechanisms: · Increased bone resorption · Increased gastrointestinal (GI) absorption of calcium · Decreased renal calcium excretion. The dominant clinical effects of significant hypercalcemia are on the nervous system, causing symptoms ranging from vague complaints to coma. Treatment of hypercalcemia of any cause can be effective, especially in the short term. The same three mechanisms that cause hypercalcemia are reversed to treat hypercalcemia: · Inhibit bone resorption · Decrease GI absorption of calcium · Increase renal excretion of calcium. A model regimen for treating hypercalcemia includes: · Hydration · Calciuresis · Administration of inhibitors of bone resorption. Saline is favored for the hydration and calciuresis unless there are cardiovascular contraindications. Calciuresis can be enhanced in the hydrated patient with loop diuretics. Salmon calcitonin (SCT) and the bisphosphonate pamidronate are used to inhibit bone resorption, with the former having early but mild effects and the latter having delayed but potent and sustained effects. Both should be used since they complement each other. Treatment of the hypercalcemia provides time for diagnosis and treatment of the underlying cause of the hypercalcemia.


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