Miller-Dieker syndrome involves a severe type of lissencephaly, which is caused 
by defects in the lissencephaly gene (LIS1). We report the case of a female 
infant with der(17)t(12;17)(q24.33;p13.3)pat caused by an unbalanced segregation 
of the parental balanced translocation of 17p with other chromosomes. The 
proband presented with facial dysmorphism, arthrogryposis, and intrauterine 
growth retardation. Most cases of Miller-Dieker syndrome have a de novo deletion 
involving 17p13.3. When Miller-Dieker syndrome is caused by an unbalanced 
translocation, mild-to-severe phenotypes occur according to the extension of the 
involved partner chromosome. However, a pure partial monosomy derived from a 
paternal balanced translocation is relatively rare. In this case, the 
submicroscopic cryptic deletion in the proband was initially elucidated by FISH, 
and karyotype analysis did not reveal additional chromosome abnormalities such 
as translocation. However, a family history of recurrent pregnancy abnormalities 
strongly suggested familial translocation. Sequential G-banding and FISH 
analysis of the father's chromosomes showed that the segment of 17p13.3→pter was 
attached to the 12qter. Thus, we report a case that showed resemblance to the 
findings in cases of a nearly pure 17p deletion, derived from t(12;17), and 
delineated by whole genome array comparative genomic hybridization (CGH). If 
such cases are incorrectly diagnosed as Miller-Dieker syndrome caused by de novo 
17p13.3 deletion, the resultant improper genetic counseling may make it 
difficult to exactly predict the potential risk of recurrent lissencephaly for 
successive pregnancies.