<prompt> A patient with pain in back. Lab investigation shows elevated ESR. X-ray skull shows multiple punched out lytic lesions. Most imp. Investigation to be done is -Serum acid phosphataseCT head with contrastWhole body scanSerum electrophoresis  <response>: This patient has : -Multiple punched-out lytic lesions of the skull.Elevated ESRBack painDiagnosis is multiple myeloma.Multiple myelomas is diagnosed by M bands on serum electrophoresis. 