8q12 microduplication syndrome

Alternate names

Dup(8)(q12); Trisomy 8q12; Chromosome 8q12 microduplication syndrome

Definition

The newly described 8q12 microduplication syndrome is associated with unusual and characteristic multi-organ clinical features, which include hearing loss, congenital heart defects, intellectual disability, hypotonia in infancy, and Duane anomaly.

Epidemiology

It has been described in two patients.

Cause

• This microduplication was identified by microarray-based comparative genomic hybridization (aCGH).
• The lack of recurrent breakpoints in these two cases and the absence of any low-copy repeats (LCR) pairs that flank these de novo events do not support non-allelic homologous recombination as the mutation mechanism.
• The 8q12 region includes CHD7 and it is proposed that this gene, associated with CHARGE syndrome by haploinsufficiency, causes a different phenotype by gain-of-dosage.

Signs and symptoms

The mild facial dysmorphism is characterized by high, arched eyebrows and unilateral narrowing of the palpebral fissure and retraction of the globe caused by Duane anomaly (Duane anomaly is a form of complex strabismus characterized by limited ocular abduction and variably limited adduction accompanied by retraction of the globe, which narrows the palpebral fissure).

Clinical presentation

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Duane anomaly
• Global developmental delay
• Long palpebral fissure(Broad opening between the eyelids)
• Muscular hypotonia(Low or weak muscle tone)
• Sensorineural hearing impairment
• Ventricular septal defect(Hole in heart wall separating two lower heart chambers)

30%-79% of people have these symptoms

• Abnormal cranial nerve morphology
• Atrial septal defect(An opening in the wall separating the top two chambers of the heart)
• Attention deficit hyperactivity disorder(Attention deficit)
• Brachycephaly(Short and broad skull)
• Epicanthus(Eye folds)
• Everted lower lip vermilion(Drooping lower lip)
• Gastroesophageal reflux(Acid reflux)
• Highly arched eyebrow(Arched eyebrows)
• Long philtrum
• Narrow mouth(Small mouth)
• Short foot(Short feet)
• Telecanthus(Corners of eye widely separated)
• Vesicoureteral reflux
• Wide nasal bridge(Broad nasal bridge)

Diagnosis

Chromosome disorders may be suspected in people who have developmental delays, intellectual disabilities and/or physical abnormalities.

Several types of genetic tests can identify chromosome disorders:

• Karyotyping
• Microarray (also called array CGH)
• Fluorescence in situ hybridization (FISH)

NIH genetic and rare disease info

• NIH info on 8q12 microduplication syndrome

8q12 microduplication syndrome is a rare disease.

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