The t(9;22) translocation in Philadelphia-positive essential thrombocythaemia does not involve the T lymphocyte lineage.
A 42-year-old woman presented with clinical and haematological features of essential thrombocythaemia (ET). Cytogenetic investigation revealed a standard t(9;22) Philadelphia translocation in all evaluable metaphases which persisted throughout treatment. Gene probe analysis of the chromosome 22 breakpoint cluster region (bcr) locus revealed a breakpoint mapping between exons 1 and 3 of the bcr gene, consistent with a standard bcr-abl translocation as found in chronic myeloid leukaemia (CML). Moreover, in separate cell populations, the bcr breakpoint was demonstrable in DNA from granulocytes but not in T cells from either peripheral blood or bone marrow. Since ET is known to be a clonal disorder with a multipotential stem cell origin, these findings suggest that, as in CML, the bcr-abl hybrid gene arises through translocation in a multilineage stem cell which does not involve the T lymphocyte lineage.
Browett
P J
PJ
Department of Haematology, Royal Free Hospital School of Medicine, London, UK.
Heslop
H E
HE
Mehta
A B
AB
Norton
J D
JD
D000328:Adult; D015703:Antigens, CD / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D017252:CD3 Complex; D002892:Chromosomes, Human, Pair 22; D002899:Chromosomes, Human, Pair 9; D004247:DNA / Q000097:blood / Q000235:genetics; D005260:Female; D006801:Humans; D009693:Nucleic Acid Hybridization; D010677:Philadelphia Chromosome; D011948:Receptors, Antigen, T-Cell / Q000032:analysis; D013601:T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D013920:Thrombocythemia, Essential / Q000097:blood / Q000235:genetics* / Q000276:immunology; D014178:Translocation, Genetic
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D011948:Receptors, Antigen, T-Cell; D004247:DNA