There is a highly significant excess of subjects with multiple clonal mosaics, compared to the Poisson distribution expected if the anomalies occurred independently. The multiples are of two kinds: (a) ‘compound’ sets of anomalies adjacent to one another on a single chromosome, suggesting a single event or related mechanism of origin (e.g. Supplementary Figure 2g) and (b) non-adjacent sets. Among the 404 mosaic subjects, 64 had multiple mosaics of one or both types (while 2.6 were expected) and 55 had only non-adjacent sets (2.4 expected). The excess of multiple mosaics occurs for both CNVs and aUPD. The age of subjects with multiple anomalies is not significantly different than those with a single anomaly (p=0.99).
