A 15-year-old male with myelodysplastic syndrome (MDS) characterized by monosomy 
7 was cytogenetically evaluated by metaphase karyotyping and fluorescence in 
situ hybridization (FISH) of interphase cells at six different points during the 
course of his disease. At diagnosis, there was complete agreement between 
metaphase and interphase findings. Interphase analysis alone provided important 
cytogenetic information on the first specimens received following intensive 
combination chemotherapy and bone marrow transplantation where metaphase 
analyses were uninformative. The detection of a minor post-treatment monosomy 7 
population by interphase but not metaphase studies may have identified minimal 
residual disease prior to recurrence of MDS. From this longitudinal study, it is 
concluded that metaphase and interphase cytogenetic analyses form complementary 
approaches and that use of both provides greater analytical power when 
appropriate chromosome markers are available.