Chromosome 6q25 microdeletion syndrome

Alternate names

6q25 microdeletion syndrome; Deletion 6q25; Monosomy 6q25

Definition

6q25 microdeletion syndrome is a recently described syndrome characterized by developmental delay, facial dysmorphism and hearing loss.

Epidemiology

It has been clinically and molecularly characterized in 4 patients.

Cause

• This syndrome is caused by an interstitial deletion encompassing 6q25.2-q25.3.
• These de novo deletions were characterized by comparative genomic hybridization (CGH) microarray and fluorescence in situ hybridization (FISH).
• They have a variable size with the smallest region of overlap (SRO) of 3.52 Mb.

Signs and symptoms

• All of them presented with microcephaly, developmental delay, dysmorphic features and hearing loss, whereas two of them had agenesis of the corpus callosum.
• Dysmorphic features include midface hypoplasia, hypertelorism, broad nasal root and posteriorly rotated ears.

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

• Global developmental delay
• Intellectual disability, mild(Mental retardation, borderline-mild)
• Microcephaly(Abnormally small skull)
• Sensorineural hearing impairment

30%-79% of people have these symptoms

• Abnormality of the pinna(Abnormally shaped ears)
• Abnormality of vision(Abnormality of sight)
• Agenesis of corpus callosum
• Downslanted palpebral fissures(Downward slanting of the opening between the eyelids)
• Epicanthus(Eye folds)
• Failure to thrive(Faltering weight)
• High palate(Elevated palate)
• Hypertelorism(Wide-set eyes)
• Low-set, posteriorly rotated ears
• Malar flattening(Zygomatic flattening)
• Plagiocephaly(Flat head syndrome)
• Short stature(Decreased body height)
• Wide nasal bridge(Broad nasal bridge)

5%-29% of people have these symptoms

• Abnormality of cardiovascular system morphology
• Camptodactyly of finger(Permanent flexion of the finger)
• Cleft palate(Cleft roof of mouth)
• Clinodactyly of the 5th finger(Permanent curving of the pinkie finger)
• External genital hypoplasia(Underdevelopment of external reproductive organs)
• Long philtrum
• Micrognathia(Little lower jaw)
• Neonatal hypotonia(Low muscle tone, in neonatal onset)
• Rocker bottom foot(Rocker bottom feet)
• Seizure
• Upslanted palpebral fissure(Upward slanting of the opening between the eyelids)
• Ventriculomegaly

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 Chromosome 6q25 microdeletion syndrome

Chromosome 6q25 microdeletion syndrome is a rare disease.