By reviewing the literature, all available reported sSMC cases (total 2,211) were collected on a regularly updated sSMC homepage [9]. All cases were included when at least the chromosomal origin of an sSMC was reported in an article listed at the National Center for Biotechnology Information webpage ( or If available, gender of the carrier, age at diagnosis, the cytogenetically studied material (blood, amniocytes, fibroblasts), parental origin of sSMC, the GTG-banding result including mosaicism of sSMC, final fluorescence in situ hybridization (FISH) results of sSMC, applied FISH methods, exclusion of uniparental disomy (UPD) for the sSMC’s sister-chromosomes and the clinical symptoms are also listed. Thus, according to this data [9], the distribution of the chromosomal origin of sSMC is summarized as available from the literature (Fig. 1). Even though this data is biased by the fact that not all but mainly ‘the interesting sSMC cases’ are published, it provides the only available insight on the chromosomes most frequently involved in sSMC-formation.

According to that data, an algorithm for a straightforward characterization of sSMC origins was worked out (as presented in Results). According to the chromosome-specific frequency of sSMC, the application of commercially available centromere specific probes is suggested to quickly achieve information on the chromosomal origin of a centric sSMC [2]. Commercially available whole chromosome painting probes can be used for the characterization of neocentric sSMC. Neocentric, also called analphoid sSMC, "carry newly derived centromeres (or "neocentromeres") that are apparently formed within interstitial chromosomal sites that have not previously been known to express centromere function" [10].