Interstitial deletions of the middle portion of the long arm of chromosome 5 are 
relatively rare. So far, only 36 cases have been reported. Because of the 
repetitive banding pattern of this region, the extent and localization of the 
deleted segment has not been well characterized in the majority of reported 
cases. This has complicated attempts to establish a definite karyotype-phenotype 
correlation. We report a further case with a de novo interstitial deletion of 
the region 5q?15 to 5q?22 identified by standard karyotype analysis. The proband 
presented with failure to thrive, developmental delay, distinct craniofacial 
dysmorphic features, and associated structural anomalies (amongst them cleft 
palate, iris colobomata, and horseshoe kidney, which have previously been 
reported in 5q deletion cases). In addition, this child had an Arnold-Chiari 
type I malformation that required surgical decompression. FISH studies using BAC 
clones spanning the 5q15 to 5q22 region revealed that these were all present in 
both homologues. Use of more distal clones allowed delineation of the deleted 
region to 5q22.3q23.3 and to narrow down the breakpoints to approximately 200 
kb. The 14 Mb deleted region contains about 60 genes but, with the possible 
exception of FBN2 and DMXL1, there are no obvious candidate genes for the 
specific components of the phenotype. This case illustrates the discrepancy 
between cytogenetic and molecular techniques in trying to delineate 5q 
interstitial deletions. Molecular studies need to be performed on these 
patients, to establish genotype-phenotype correlation and to understand the role 
and influence of genes in this region.