Chromosome 8p23.1 deletion

Alternate names

8p23.1 microdeletion syndrome; Deletion 8p23.1; Monosomy 8p23.1; 8p23.1 deletion

Definition

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.

Cause

• 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.

Inheritance

• 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.

Signs and symptoms

• 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.

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)
• Intrauterine growth retardation(Prenatal growth deficiency)

30%-79% of people have these symptoms

• Atrioventricular canal defect
• Attention deficit hyperactivity disorder(Attention deficit)
• Biparietal narrowing
• Cryptorchidism(Undescended testes)
• Enlarged thorax(Wide rib cage)
• Epicanthus(Eye folds)
• External ear malformation
• High forehead
• High palate(Elevated palate)
• Hypospadias
• Low-set ears(Low set ears)
• Microcephaly(Abnormally small skull)
• Micrognathia(Little lower jaw)
• Poor speech
• Pulmonary artery stenosis(Narrowing of lung artery)
• Seizure
• Short neck(Decreased length of neck)
• Short nose(Decreased length of nose)
• Short stature(Decreased body height)
• Tapered finger(Tapered fingertips)
• Weight loss
• Wide intermamillary distance(Wide-spaced nipples)
• Wide nasal bridge(Broad nasal bridge)

Diagnosis

• 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). Accurate chromosomal analysis confirms the differential diagnosis.

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

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.

NIH genetic and rare disease info

• NIH info on Chromosome 8p23.1 deletion

Chromosome 8p23.1 deletion is a rare disease.

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