Persistent expression of nonclinical and/or clinical isotypes at diagnosis and throughout the course of disease.

Nonclinical isotypes are detectable in a single-stage RT-PCR (strategy A). Patient 1 was followed from diagnosis in December 1996 to June 1999. She was treated with melphalan and prednisone from diagnosis until April 1998. She was on dexamethasone therapy from April 1998 until her death in November 1999 from MM-related BM failure and sepsis. Her treatment was only of modest clinical benefit. Her clinical isotype was IgG. The top panels show RT-PCR results using strategy A and the bottom panels show results using strategy B. This patient is representative of those having nonclinical clonotypic isotype expression sufficiently frequent to be detected in a single-stage PCR reaction. Some samples that were negative with strategy A, became positive when tested using nested PCR (strategy B). All samples were positive for expression of the patient-specific VDJ gene rearrangement (strategy D). BM indicates bone marrow samples; c, control lanes lacking cDNA.