This syndrome is a chromosome abnormality. A chromosome is a rod-like structure present in the nucleus of all body cells, with the exception of the red blood cells, and which stores genetic information. Normally humans have 23 pairs of chromosomes, the unfertilised ova and each sperm carrying a set of 23 chromosomes. A normal female has an XX pair and a normal male an XY pair. Increases or decreases in chromosome material interfere with normal body formation and development.
Chromosome abnormalities give rise to specific physical features.
In most cases of Cri du Chat Syndrome there is a simple deletion of the short arm of chromosome 5. Characteristic features of the syndrome are a high pitched cat-like cry in infancy, low birth weight, some delay in reaching milestones, and, in some cases, feeding difficulties. Heart defects are also associated with the condition, examples of which are ventricular septal defect or patent ductus arteriosis. Inheritance patterns Most cases are sporadic. In some rare cases a balanced translocation or another chromosome abnormality in a parent may result in an affected child.