Chromosomal instability in incontinentia pigmenti: study of four families.

Cytogenetic studies in four patients affected by Incontinentia pigmenti and in their relatives did not show a significant increase of chromatid and chromosome gaps and breaks. This seems to negate a correlation between these findings and the disease. We propose that the responsibility for the chromosomal breakages sometimes observed in this syndrome can be due to external factors that disturb the basal percentage of the lesions.