Recombinant chromosome 8 syndrome

Alternate names

Rec8 syndrome; San Luis Valley recombinant chromosome 8 syndrome; San Luis Valley syndrome

Definition

Recombinant chromosome 8 syndrome is a condition that involves heart and urinary tract abnormalities, moderate to severe intellectual disability, and a distinctive facial appearance. Many children with recombinant chromosome 8 syndrome do not survive past early childhood, usually due to complications related to their heart abnormalities.

Epidemiology

• Recombinant 8 syndrome is a rare condition; its exact incidence is unknown.
• Most people with this condition are descended from a Hispanic population originating in the San Luis Valley area of southern Colorado and northern New Mexico.
• Recombinant 8 syndrome is also called San Luis Valley syndrome.
• Only a few cases outside this population have been found.

Cause

• Recombinant 8 syndrome is caused by a rearrangement of chromosome 8 that results in a deletion of a piece of the short (p) arm and a duplication of a piece of the long (q) arm.
• The deletion and duplication result in the recombinant 8 chromosome.
• The signs and symptoms of recombinant 8 syndrome are related to the loss and addition of genetic material on these regions of chromosome 8.
• Researchers are working to determine which genes are involved in the deletion and duplication on chromosome 8.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

• This condition is inherited in an autosomal dominant pattern, which means one copy of the recombinant chromosome 8 in each cell is sufficient to cause the disorder.
• Most people with recombinant 8 syndrome have at least one parent with a change in chromosome 8 called an inversion.
• An inversion involves the breakage of a chromosome in two places; the resulting piece of DNA is reversed and reinserted into the chromosome.
• Genetic material is typically not lost as a result of this inversion in chromosome 8, so people usually do not have any related health problems.
• However, genetic material can be lost or duplicated when inversions are being passed to the next generation.
• People with this chromosome 8 inversion are at of risk having a child with recombinant 8 syndrome.

Signs and symptoms

• The characteristic facial features include a wide, square face; a thin upper lip; a downturned mouth; a small chin (micrognathia); wide-set eyes (hypertelorism); and low-set or unusually shaped ears.
• People with recombinant 8 syndrome may have overgrowth of the gums (gingival hyperplasia) and abnormal tooth development. Males with this condition frequently have undescended testes (cryptorchidism).
• Some affected individuals have recurrent ear infections (otitis media) or hearing loss.
• Many children with recombinant 8 syndrome do not survive past early childhood, usually due to complications related to their heart abnormalities.

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

• Abnormality of the dentition(Abnormal dentition)
• Anteverted nares(Nasal tip, upturned)
• Cryptorchidism(Undescended testes)
• Deep plantar creases(Deep wrinkles in soles of feet)
• Downturned corners of mouth(Downturned corners of the mouth)
• Global developmental delay
• Hypertelorism(Wide-set eyes)
• Intellectual disability(Mental deficiency)
• Large face(Big face)
• Low posterior hairline(Low hairline at back of neck)
• Micrognathia(Little lower jaw)
• Redundant skin(Loose redundant skin)

30%-79% of people have these symptoms

• Abnormal oral frenulum morphology
• Abnormality of the kidney(Abnormal kidney)
• Atrial septal defect(An opening in the wall separating the top two chambers of the heart)
• Bilateral single transverse palmar creases
• Camptodactyly of finger(Permanent flexion of the finger)
• Chronic otitis media(Chronic infections of the middle ear)
• Clinodactyly of the 5th finger(Permanent curving of the pinkie finger)
• Depressed nasal bridge(Depressed bridge of nose)
• Gingival overgrowth(Gum enlargement)
• Hearing impairment(Deafness)
• Low-set ears(Low set ears)
• Patellar aplasia(Absent kneecap)
• Patent ductus arteriosus
• Pectus excavatum(Funnel chest)
• Pulmonary artery stenosis(Narrowing of lung artery)
• Scoliosis
• Scrotal hypoplasia(Smaller than typical growth of scrotum)
• Seizure
• Spasticity(Involuntary muscle stiffness, contraction, or spasm)
• Tetralogy of Fallot
• Thick vermilion border(Full lips)
• Ventricular septal defect(Hole in heart wall separating two lower heart chambers)

5%-29% of people have these symptoms

• Abnormality of the anus
• Abnormality of vision(Abnormality of sight)
• Cleft palate(Cleft roof of mouth)
• Cleft upper lip(Harelip)

Diagnosis

Postnatal chromosomal microarray and other studies identified a de novo derivative chromosome 8. For fetal anomalies, detailed genetic studies may be required. Brain MR revealed multiple abnormalities primarily affecting midline structures, including commissural dysgenesis, vermian and brainstem hypoplasia/dysplasia, an interhypothalamic adhesion, and an epidermoid between the frontal lobes that enlarged over time. Spine MR demonstrated hypoplastic C1 and C2 posterior elements, scoliosis, and a borderline low conus medullaris position.

NIH genetic and rare disease info

• NIH info on Recombinant chromosome 8 syndrome

Recombinant chromosome 8 syndrome is a rare disease.

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