Partial 7Q deletion in a prenatal sample: Case study and review.

Deletion of the distal region of the long arm of chromosome 7 is a rarely diagnosed abnormality with a varied and complex phenotype. Most deletions are terminal with breakpoints at 7q35 or 7q36, and include the SHH(sonic hedgehog) gene located at 7q36.3. This gene is important in development of the brain, central nervous system, eyes and limbs. Monosomy for this gene can cause holoprosencephaly which, in addition to hydronephrosis, growth retardation and sacral agenesis, is a commonly described feature of this chromosomal abnormality. The majority of deletions are de novo, although some have been identified as a result of malsegregation of a parental translocation involving chromosome 7. An amniocentesis was performed following detection of short long bones, hydronephrosis and coarctation of the aorta on ultrasound scan. Holoprosencephaly was not detected. CGH-microarray analysis revealed a copy number loss of 7q36.1 to 7q36.3. Genotype-phenotype correlations between this case and other published cases will be discussed.