Review Question - QID 217072

This patient with acute renal failure (as indicated by elevated creatinine, elevated BUN, hyperkalemia, pruritus likely secondary to uremia, anion gap of 17 likely secondary to uremia), anemia without pancytopenia, hypercalcemia, and possible bone pain, most likely has multiple myeloma (MM). Bone marrow biopsy in patients with MM will generally show greater than 10% proliferation of monoclonal plasma cells.

Multiple myeloma is a malignant proliferation of monoclonal plasma cells. The cause of MM is not known, and it is rarely possible to distinguish malignant from benign plasma cells by morphology alone. MM causes lytic bony lesions by proliferation of tumor cells in the marrow, suppression of osteoblasts, and activation of osteoclasts by MM cells. Bone destruction can also lead to hypercalcemia. As MM cells are plasma cells, they secrete antibodies (usually IgG or IgA). These antibodies can aggregate in kidney tubules forming casts that lead to acute renal failure in 25% of cases and varying levels of renal dysfunction in greater than 50% of cases (myeloma kidney). MM cell expansion in the bone marrow in combination with decreased production of erythropoietin by the kidney leads to anemia in greater than 80% of cases of MM. MM can be diagnosed via a bone marrow biopsy that demonstrates a monoclonal proliferation of malignant plasma cells.

Van de Donk et al. review the epidemiology, pathogenesis, genomics, symptoms, diagnostic investigation, and therapy for multiple myeloma.

Incorrect Answers:
Answer 1: B-cells with filamentous, hair-like projections on peripheral blood smear are found in hairy cell leukemias. These tumors are generally found in adult males and cause marrow fibrosis, massive splenomegaly due to expansion of the red pulp, and pancytopenia. In this patient with anemia without pancytopenia, hypercalcemia, and renal failure, MM is more likely than hairy cell leukemia.

Answer 2: CD20+, CD23+, CD5+ B-cells on peripheral blood smear are found in chronic lymphocytic leukemia and small lymphocytic lymphoma. These cancers generally progress slowly, are associated with autoimmune hemolytic anemia, and undergo a Richter transformation into an aggressive diffuse large B-cell lymphoma. They typically do not present with acute renal failure or hypercalcemia.

Answer 4: Less than 10% proliferation of monoclonal plasma cells on bone marrow biopsy is generally seen in monoclonal gammopathy of undetermined significance (MGUS). Patients with MGUS by definition do not have findings of hypercalcemia, renal dysfunction, anemia, or bone lesions. MGUS may develop into MM at a rate of 1-2% per year.

Answer 5: Monoclonal plasma cells producing IgM on bone marrow biopsy are found in Waldenstrom macroglobulinemia. Clinically, Waldenstrom macroglobulinemia presents with hyperviscosity syndrome (blurred vision, Raynaud phenomenon), but does not present with hypercalcemia, anemia, renal dysfunction, or bone lesions. Although this disease may show an M spike on serum electrophoresis similar to MM, there is overproduction of IgM instead of the IgG or IgA more typically found in MM.

Bullet Summary:
Multiple myeloma is a cancer of plasma cells that arises in the bone marrow and can manifest clinically with hypercalcemia, anemia, renal failure, and lytic bone lesions.