Ans: c (IgE) Ref: Harrison's, 16th ed, p. 657; 17th, ed, p. 703Multiple myeloma represents a malignant proliferation of plasma cells derived from a single clone. The serum M component is IgG in 53% of patients, IgA in 25% and IgD in 1 %. IgE is very rare. The most common translocation is t( 11:14).Myeloma is more commonly seen than expected among farmers, wood workers, leather workers, and those exposed to petroleum products.Bone pain is the most common symptom in multiple myeloma, effecting nearly 70% of patients.Hypercalcaemia is the most common cause of renal failure. The earliest manifestation of tubular damage is the adult Fanconi syndrome.Anaemia in multiple myeloma is normocytic normochromic and occurs in about 80% of patients.The classical triad of multiple myeloma is:Marrowplasmacytosis (.>10%),Lytic lesions, andSerum and/or urine M component.Diagnosis of multiple myeloma (The Dune and Salmon myeloma diagnostic criteria).The diagnosis of multiple myeloma requires a minimum of one major and one minor criteria or three minor criteria as defined in the Table belowMajor criteria1) Plasmacytoma on tissue biopsy2) Bone marrow palsmacytosis with 30% plasma cells3) Monoclonal globulin spike (M protein) on SPEP:IgG>3.5 g/dl,IgA > 2.0g/dl, light chain excretion on UPEP >= 1 g per 24 hr in the absence of amylodosisMinor criteriaa) Bone marrow plasmacytosis with 10-30% plasma cellsb) Monclonal globulin spike present ,but lower levels than defined in major criteriac) Lytic bone lesionsd) Normal IgM >50 mg/dl, IgA > 100 mg/dl, or IgG >600 mg/dlThe diagnosis of myeloma requires a minimum of one major criteria and one minor criteria (although 1 +a is not sufficient) or three minor criteria that must include a+b (SPEP-serum protein electrophoresis, UPEP-urineprotein electrophoresis)