Chromosome markers and evidence for clone formation in lymphocytes of a patient with Sézary syndrome.

Cytogenetic studies of 222 metaphase lymphocytes stimulated by phytohemagglutinin were carried out on a patient diagnosed clinically as having Sézary syndrome. Twenty-two cells (10%) contained 42 to 100 chromosomes. The remaining 200 cells contained 46 chromosomes and revealed evidence of clone formation; 45 were apparently normal diploid cells, but 155 were pseudodiploid with at least one long submetacentric marker in each cell. This marker was shown to have a consistent banding pattern from cell to cell. Of the 25 pseudodiploid cells karyotyped, there were other types of markers present. Normal chromosomes 2 and 17 were missing in all 25 karyotypes. There were seven set of two cells, each with an identical karyotype, suggesting subclonal formation. Many of the phytohemagglutinin-stimulated nondividing white blood cells had one or more nuclear protrusions. Cytogenetic examination of peripheral lymphocytes may be of value in diagnosing and following the course of this disease.