TRISOMY 8 MOSAICISM: CELL CYCLE KINETICS AND ...

T8m features are variable, however, some anomalies are more common than
others. The severity of the phenotypes in T8m patients is not directly related to the level
of mosaicism found (Riccardi 1977; Berry et al.1978; Swisshelm et al. 1981; Kurtyka et
al. 1988). Several cases of similar mosaicism levels have been compared, however the
patient phenotypes differ. For example, one patient had 100% trisomy 8 cells in
lymphocytes and over 60% in fibroblasts with a near normal phenotype and IQ (James
and Jacobs 1996). Comparatively, another patient was diagnosed with 94% trisomy 8
cells in lymphocytes and 70% in fibroblasts and had severe mental retardation and
various skeletal anomalies (Jordan et al. 1998). The exact mechanism which causes the
severity of phenotype in T8m patients is unknown, but believed to be associated with
either the “post zygotic origin of the trisomic status” (Miller et al 1997) or dependent
upon the contribution of aneuploid cells in the development of different tissues (Kurtyka
et al. 1988).
T8m is associated with disappearing mosaicism over time. The percentage of
trisomic cells decreases in a patient when tested several months to years after the initial
testing (La Marche 1967; Mark and Bier 1997). Jordan et al. in 1998 described two cases
showing disappearing T8m. Patients were analyzed over an 8 and 9 year period to
evaluate any change in trisomy 8 cell percentages. Both cases were shown to have a
significant decrease of trisomy 8 cells in cultured lymphocytes. Kurtyka et al. (1988) also
reported cases with similar disappearance of trisomy 8 cells in lymphocytes. Mark and
Bier (1997) suggested the trisomic line may disappear completely if enough time has
gone by. The decrease in trisomic cells has been attributed to a selective growth
advantage of the normal cells (La Marche et al. 1967; Mark and Bier 1997).
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