A clinical report of a patient with two abnormal cell lines: 46,XX,del(21)(q22.1) and 47,XX,+3.

Mosaicism for two chromosomally abnormal cell lines in the absence of a normal cell line is exceedingly rare. We report a patient with developmental and growth delay, mild dysmorphic features, a history of hypertension and hepatoblastoma who was found to be mosaic for two chromosomally abnormal cell lines. The cell lines, one containing a terminally deleted chromosome 21, the other trisomy 3, were found in her blood. Fibroblasts and hepatoblastoma tumor cells revealed only the presence of the deleted 21 cell line. Microsatellite marker analysis suggests a mosaic rather than chimeric etiology for the cell lines. This case is exceptional in that the presence of either of these two cell lines alone is uncommon; finding both of these cell lines in an individual appears to be unique.