complex small supernumerary marker chromosomes ssmc constitute one of the smallest subgroups of ssmc in general complex ssmc consist of chromosomal material derived from more than one chromosome the best known representative of this group is the derivative chromosome 22 der 22 t 11 22 or emanuel syndrome in 2008 we speculated that complex ssmc could be part of an underestimated entity here the overall yet reported 412 complex ssmc are summarized they constitute 8 4 of all yet in detail characterized ssmc cases the majority of the complex ssmc is contributed by patients suffering from emanuel syndrome 82 besides there are a der 22 t 8 22 q24 1 q11 1 and a der 13 t 13 18 q11 p11 21 or der 21 t 18 21 p11 21 q11 1 der 13 or 21 t 13 or 21 18 syndrome the latter two represent another 2 6 and 2 2 of the complex ssmc cases respectively the large majority of complex ssmc has a centric minute shape and derives from an acrocentric chromosome nonetheless complex ssmc can involve material from each chromosomal origin most complex ssmc are inherited form a balanced translocation in one parent and are non mosaic interestingly there are hot spots for the chromosomal breakpoints involved complex ssmc need to be considered in diagnostics especially in non mosaic centric minute shaped ssmc as yet three complex ssmc associated syndromes are identified as recurrent breakpoints in the complex ssmc were characterized it is to be expected that more syndromes are identified in this subgroup of ssmc overall complex ssmc emphasize once more the importance of detailed cytogenetic analyses especially in patients with idiopathic mental retardation.