The importance of high resolution chromosome analysis in the diagnosis of birth defects: case reports of holoproscencephaly and cystic hygroma.
BACKGROUND
The goal of cytogenetics is the detection of chromosomal abnormalities, achieved by the analysis of adequate numbers of metaphases at the appropriate bands per haploid set (BPHS).


METHODS
Two cases presented here include a foetal blood sample (FBS) of a 33-week-old referred with holoproscencephaly by ultrasonography, and an amniotic fluid (AF) specimen of a 14-week-old foetus with cystic hygroma, cardiac and renal defects.


RESULTS
The FBS had a deletion at 18p11.31. Another laboratory had earlier given a normal cytogenetic result on its AF sample. In the second case, an unbalanced 46,XY,der(5)ins(5;3) (q33.1;q26.2q27)mat karyotype was obtained with the AF sample. In both cases, the abnormalities were more obvious when band levels were > or =450 BPHS.


CONCLUSIONS
This report underscores the importance of obtaining longer chromosome preparations above the current recommended 400 BPHS for prenatal specimens. This is particularly important in cases with abnormal ultrasound findings suggestive of an underlying chromosomal pathology.
Department of Pathology, Singapore General Hospital, Outram Road, Singapore 169608. gptlst@sgh.com.sg
A S
AS
Lim
P
P
Chia
S K
SK
Kee
S
S
Raman
S L
SL
Tien
D000328:Adult; D000653:Amniotic Fluid; D002871:Chromosome Banding; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics; D004251:DNA Transposable Elements; D005260:Female; D015321:Gene Rearrangement; D016142:Holoprosencephaly / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics; D006801:Humans; D018191:Lymphangioma, Cystic / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics; D011247:Pregnancy; D016216:Ultrasonography, Prenatal
D004251:DNA Transposable Elements