8p23.1 Microdeletion Syndrome

8p23.1 deletion involves a partial deletion of the short arm of chromosome 8 characterized by low birth weight, postnatal growth deficiency, mild intellectual deficit, hyperactivity, craniofacial abnormalities, and congenital heart defects.

Epidemiology

The prevalence is unknown but 8p23.1 deletions are rare. To date, over 50 cases of interstitial or terminal 8p23.1 have been reported without a notable gender discrepancy.

Clinical description

The clinical manifestations are variable and do not depend on the size of the deletion, since this is the same in the majority of patients. Most common manifestations include prenatal and postnatal growth retardation, low birth weight, mild to moderate intellectual deficit, psychomotor retardation, poor speech, seizures, behavioral problems such as hyperactivity and impulsiveness. Frequent craniofacial abnormalities include microcephaly, high and narrow forehead, broad nasal bridge, epicanthic folds, high arched palate, short neck and low set unusually shaped ears. Furthermore congenital heart defects (atrioventricular, septal defects, pulmonary stenosis), congenital diaphragmatic hernia and in boys cryptorchidism and hypospadias have been frequently reported. Some affected individuals have been reported to have normal intelligence.

Etiology

The 8p23.1 deletion is likely to arise through non-allelic homologous recombination mediated by flanking low-copy repeats (LCRs), explaing the common size of approximately 3.4 Mb. The congenital heart defects and diaphragmatic hernia are most likely explained by haploinsufficiency for GATA4.

Diagnostic methods

Diagnosis is based on clinical manifestations leading to chromosomal analysis. 8p23.1 deletions are often missed by standard karyotyping, and mostly detected by molecular karyotyping. Molecular techniques may be used for the genetic characterization of the deletion (FISH, MLPA, aCGH).

Differential diagnosis

Differential diagnosis includes monosomy 22q11 (velocardiofacial syndrome; see this term). Accurate chromosomal analysis confirms the differential diagnosis.

Antenatal diagnosis

Prenatal diagnosis is possible by amniocentesis or chorionic villus sampling and molecular cytogenetic analysis.

Genetic counseling

Genetic counseling is recommended. Most 8p23.1 deletions occur de novo. However, parents can carry and transmit the chromosomal rearrangement to their children as well, with a risk of 50% for each child.

Management and treatment

Management involves assessment, treatment and a regular follow-up by appropriate specialists, including a general practitioner, pediatrician and cardiologists. Early diagnosis and access to major developmental therapies aiming at obtaining the best developmental outcome have been proven beneficial.

Prognosis

Life expectancy is considered normal provided that there is no major congenital heart anomaly or a diaphragmatic hernia.