tailieunhanh - Chapter 106. Plasma Cell Disorders (Part 5)

Anemia occurs in ~80% of myeloma patients. It is usually normocytic and normochromic and related both to the replacement of normal marrow by expanding tumor cells and to the inhibition of hematopoiesis by factors made by the tumor. In addition, mild hemolysis may contribute to the anemia. A larger than expected fraction of patients may have megaloblastic anemia due to either folate or vitamin B12 deficiency. Granulocytopenia and thrombocytopenia are very rare. Clotting abnormalities may be seen due to the failure of antibody-coated platelets to function properly or to the interaction of the M component with clotting factors I,. | Chapter 106. Plasma Cell Disorders Part 5 Anemia occurs in 80 of myeloma patients. It is usually normocytic and normochromic and related both to the replacement of normal marrow by expanding tumor cells and to the inhibition of hematopoiesis by factors made by the tumor. In addition mild hemolysis may contribute to the anemia. A larger than expected fraction of patients may have megaloblastic anemia due to either folate or vitamin B12 deficiency. Granulocytopenia and thrombocytopenia are very rare. Clotting abnormalities may be seen due to the failure of antibody-coated platelets to function properly or to the interaction of the M component with clotting factors I II V VII or VIII. Deep venous thrombosis is also observed with use of thalidomide or lenalidomide in combination with dexamethasone. Raynaud s phenomenon and impaired circulation may result if the M component forms cryoglobulins and hyperviscosity syndromes may develop depending on the physical properties of the M component most common with IgM IgG3 and IgA paraproteins . Hyperviscosity is defined on the basis of the relative viscosity of serum as compared with water. Normal relative serum viscosity is . serum is normally almost twice as viscous as water . Symptoms of hyperviscosity occur at a level of 5-6 a level usually reached at paraprotein concentrations of 40 g L 4 g dL for IgM 50 g L 5 g dL for IgG3 and 70 g L 7 g dL for IgA. Although neurologic symptoms occur in a minority of patients they may have many causes. Hypercalcemia may produce lethargy weakness depression and confusion. Hyperviscosity may lead to headache fatigue visual disturbances and retinopathy. Bony damage and collapse may lead to cord compression radicular pain and loss of bowel and bladder control. Infiltration of peripheral nerves by amyloid can be a cause of carpal tunnel syndrome and other sensorimotor mono- and polyneuropathies. Sensory neuropathy is also a side effect of thalidomide and bortezomib therapy. Many of the