8p23.1 duplication syndrome

8p23.1 duplication syndrome
Other names	Dup(8)(p23.1p23.1), Trisomy 8p23.1
Chromosome 8 is associated with this condition

8p23.1 duplication syndrome is a rare genetic disorder caused by a duplication of a region from human chromosome 8.^[1] This duplication syndrome has an estimated prevalence of 1 in 64,000 births^[1] and is the reciprocal of the 8p23.1 deletion syndrome. The 8p23.1 duplication is associated with a variable phenotype including one or more of speech delay, developmental delay, mild dysmorphism, with prominent forehead and arched eyebrows, and congenital heart disease (CHD).^[2][3]

Presentation

The phenotypic data on 11 patients indicated that cases are not always ascertained for

but not in the duplicated mother of one of them. The phenotype is compatible with independent adult life with varying degrees of support. Duplication of the found in the 8p23.1 deletion syndrome has not been found in the 8p23.1 duplication syndrome to date. The duplication may be associated with copy number changes of the adjacent olfactory receptor/defensin repeats (ORDRs) that predispose to the 8p23.1 deletion and duplication syndromes. High total copy numbers of these repeats have been associated with predisposition to psoriasis^[6] and low copy number with predisposition to Crohn's disease.^[7]

Genetics

The duplication includes ~3.75 Mb between the distal and proximal ORDRs at either end of band 8p23.1. The copy number of the adjacent repeats may also be altered. The 8p23.1 duplication syndrome cannot be distinguished using conventional cytogenetics from high level copy number variation of the repeats themselves.^[1][2]

Both de novo cases and families with transmitted duplications from parents of both sex are known. The duplication is believed to arise de novo as a result of non-allelic homologous recombination (NAHR) between the proximal and distal ORDRs. NAHR is also thought to give rise to the reciprocal microdeletion syndrome, the polymorphic inversion between the ORDRs and a variety of other large scale abnormalities involving the short arm of chromosome 8.^[6]

Diagnosis

Phenotypes

Primary	Secondary	Tertiary
NEUROLOGY	MENTAL, COGNITIVE FUNCTION, general abnormalities	intellectual disability/developmental delay
VOICE	Voice, general abnormalities	Speech delay

See also

• Chromosome 8 (human)

References

External links

• DECIPHER database description