PH-POSITIVE CML IN BLASTIC PHASE WITH MONOSOMY-7 IN A DOWN-SYNDROME PATIENT - MONITORING BY INTERPHASE CYTOGENETICS AND DEMONSTRATION OF MATERNAL ALLELIC LOSS

We report a case of Ph-positive chronic myelocytic leukemia in blastic phase in an 11-year-old boy with Down syndrome. Monosomy 7 was the on ly additional chromosomal anomaly in the blastic clone. Fluorescence i n situ hybridization analysis on interphase nuclei with a centromeric probe specific to chromosome 7 proved to be efficient in disease monit oring, and showed, together with the results of chromosome analysis on metaphases, that B-lymphocytes at the origin of an EBV-established li ne were not part of the leukemic clone. The study of DNA polymorphisms showed that the origin of the constitutional trisomy 21 was a materna l anaphase I nondisjunction, that the chromosome 7 lost in the blastic marrow clone was the maternal one, and led us to postulate that the m other's chromosomes are prone to impairment of normal disjunction. The study of allelic losses of chromosome 7 loci proved to be a further p ossibility for disease monitoring. (C) Elsevier Science Inc., 1997.