A complex five breakpoint intrachromosomal rearrangement ascertained through two recombinant offspring.

Intrachromosomal rearrangements usually result from three of fewer breaks. We report a complex intrachromosomal rearrangement resulting from five breaks in one chromosome 10 of a phenotypically normal father of two developmentally delayed children. GTG-banding analysis of the father's rearranged chromosome 10 suggested in initial pericentric inversion followed by an insertion from the short arm into the terminal band of the long arm [der(10) (pter-->p13::q21.2-->p12.2::q22.1::-->q26.3::q22.1-->q 21.2::p12.2-->p13::q26.3-->qter)]. To our knowledge, this rearrangement is the most complex ever reported in a single chromosome. Both children inherited a recombinant chromosome 10 with loss of the insertion and the segment distal to it [rec(10)der(pter-->p13: :q21.2-->p12.2::q22.1-->q26.3:)]. Mechanisms for both rearrangements are proposed.