Chromosomal deletion syndrome

Chromosomal deletion syndromes result from deletion of parts of chromosomes. Depending on the location, size, and whom the deletion is inherited from, there are a few known different variations of chromosome deletions. Chromosomal deletion syndromes typically involve larger deletions that are visible using karyotyping techniques. Smaller deletions result in Microdeletion syndrome, which are detected using fluorescence in situ hybridization (FISH) Chromosomal deletion syndromes result from deletion of parts of chromosomes. Depending on the location, size, and whom the deletion is inherited from, there are a few known different variations of chromosome deletions. Chromosomal deletion syndromes typically involve larger deletions that are visible using karyotyping techniques. Smaller deletions result in Microdeletion syndrome, which are detected using fluorescence in situ hybridization (FISH) Examples of chromosomal deletion syndromes include 5p-Deletion (cri du chat syndrome), 4p-Deletion (Wolf-Hirschhorn syndrome), Prader–Willi syndrome, and Angelman syndrome. The chromosomal basis of Cri du chat syndrome consists of a deletion of the most terminal portion of the short arm of chromosome 5. 5p deletions, whether terminal or interstitial, occur at different breakpoints; the chromosomal basis generally consists of a deletion on the short arm of chromosome 5. The variability seen among individuals may be attributed to the differences in their genotypes. With an incidence of 1 in 15,000 to 1 in 50,000 live births, it is suggested to be one of the most common contiguous gene deletion disorders. 5p deletions are most common de novo occurrences, which are paternal in origin in 80–90% of cases, possibly arising from chromosome breakage during gamete formation in males Some examples of the possible dysmorphic features include: downslanting palpebral fissures, broad nasal bridge, microcephaly, low-set ears, preauricular tags, round faces, short neck, micrognathia, and dental malocclusionhypertelorism, epicanthal folds, downturned corners of the mouth. There is no specific correlation found between size of deletion and severity of clinical features because the results vary so widely. The chromosomal basis of Wolf-Hirschhorn syndrome (WHS) consists of a deletion of the most terminal portion of the short arm of chromosome 4. The deleted segment of reported individuals represent about one half of the p arm, occurring distal to the bands 4p15.1-p15.2. The proximal boundary of the WHSCR was defined by a 1.9 megabase terminal deletion of 4p16.3. This allele includes the proposed candidate genes LEMT1 and WHSC1. This was identified by two individuals that exhibited all 4 components of the core WHS phenotype, which allowed scientists to trace the loci of the deleted genes. Many reports are particularly striking in the appearance of the craniofacial structure (prominent forehead, hypertelorism, the wide bridge of the nose continuing to the forehead) which has led to the descriptive term “Greek warrior helmet appearance.