Recently it has been shown that most cases of the Miller-Dieker syndrome (MDS) 
are caused by deletion 17p13.3. All familial cases have been associated with a 
balanced reciprocal translocation in a carrier parent and unbalanced 
translocations in their affected offspring. We report a new case of familial MDS 
in whom the mother carries a pericentric inversion of chromosome 17. She has had 
two children with MDS, one of whom was shown to carry a recombinant 17 
consisting of dup(17q) and del(17p). The high frequency of familial MDS and its 
consistent association with balanced chromosomal rearrangements in one of the 
parents makes it important to do high-resolution chromosome analysis on all 
patients with MDS and possibly all patients with lissencephaly. Finding a 
familial balanced rearrangement makes prenatal diagnosis of this condition 
feasible.