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Recombinant 8 syndrome
Recombinant 8 (rec(8)) syndrome, also known as San Luis Valley syndrome, is a complex chromosomal disorder that is due to a parental pericentric inversion of chromosome 8 and is characterized by major congenital heart anomalies, urogenital malformations, moderate to severe intellectual deficiency and mild craniofacial dysmorphism.
The prevalence is unknown but the syndrome is rare. Rec(8) syndrome occurs typically in people with Hispanic ancestry from the Southwestern United States and is thought to be due to a single founder who emigrated from Spain to Colorado or New Mexico in the 17th or 18th century.
Rec(8) syndrome is characterized by major congenital heart anomalies, comprising complex conotruncal abnormalities often accompanied by patent ductus arteriosus or persistent left superior vena cava (PLSVC) or nonconotruncal anomalies including pulmonic stenosis, ventricular septal defect (VSD), patent ductus arteriosus and PLSVC; urogenital malformations such as cryptorchidism and hypoplastic scrotum in males; moderate intellectual disability; and mild craniofacial dysmorphism including abnormal hair whorl, low posterior hairline, wide face, hypertelorism, infraorbital creases, anteverted nares, thin upper lip, downturned mouth, gingival hyperplasia, abnormal tooth development, micrognathia, mal-shaped and low-set ears. Other findings include developmental delay, spasticity, leading to orthopedic complications such as scoliosis, seizures and recurring otitis media or hearing loss. Individuals with rec(8) syndrome generally present solid social and nonverbal communication skills and an overall good nature despite their intellectual disability.
Rec(8) syndrome is a complex chromosomal disorder, rec(8)dup(8q)inv(8)(p23.1q22.1) due to a parental pericentric inversion of chromosome 8 [inv(8)(p23.1q22.1)] with presumed constant breaking points in this Hispanic population and variants in other populations.
Diagnosis is based on clinical manifestations leading to chromosomal analysis by classical or molecular karyotyping.
Differential diagnoses include other chromosomal anomalies involving chromosome 8, Bardet-Biedl syndrome, Williams syndrome and Noonan syndrome (see these terms).
Prenatal diagnosis is possible by amniocentesis or chorionic villus sampling and cytogenetic analysis.
Genetic counseling is recommended and needs karyotyping of the parents in order to evaluate the risk of recurrence. Segregation analysis has ascertained a 6.2% risk for a carrier parent to have a child with rec(8) syndrome with the transmission rate being higher in carrier mothers (59%) than fathers (42%).
Management and treatment
Management involves cardiac surgery in case of cardiac malformations and a multidisciplinary approach including hearing screening, evaluation of reflux and constipation and full developmental assessment with periodic follow-up. Regular neurodevelopmental screening and participation in individually adapted therapy programs are recommended. Orthopedic surgery has been shown to give suboptimal results due to the intellectual deficit impeding rehabilitation.
Prognosis is variable, depending on the severity of congenital heart disease. Historically, life expectancy past early childhood was very low, however with the increased quality and early treatment intervention the majority may live into adulthood. Exact life expectancy is unknown.
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- Russian (2012, pdf)