Distal Trisomy 10q

Distal trisomy of the long arm of chromosome 10 (10q) is characterized by pre- and postnatal growth retardation, a pattern of specific facial features, hypotonia, and developmental and psychomotor delay.

Epidemiology

To date, approximately 40 cases of trisomy 10q have been reported.

Clinical description

Most cases are diagnosed in infancy or in childhood. The range and severity of symptoms and physical findings may vary from case to case, depending upon the exact length and location of the duplicated portion of chromosome 10q. Characteristic craniofacial findings include a flat round face with full cheeks and a large prominent forehead, highly arched eyebrows, short and narrow palpebral fissures (blepharophimosis), widely spaced eyes with telecanthus, a short nose, a bow-shaped mouth with a prominent upper lip, and a small mandible. A few major malformations have also been reported, including renal and cardiac anomalies. Minor defects of the hands and/or feet, bone anomalies and cryptorchidism are frequent signs.

Etiology

The duplicated region almost always includes 10qter, with the most frequent proximal breakpoint at 10q24 (with variation from q22 to q25). Interstitial duplications of 10q have also been reported. Most cases of distal trisomy 10q result from of a parental balanced translocation or pericentric inversion, and may be accompanied by another chromosomal imbalance. Intrachromosomal duplications or de novo translocations are also observed.

Diagnostic methods

Diagnosis is suspected on the basis of the clinical features and is confirmed by karyotyping and fluorescence in situ hybridization (FISH) with specific 10q probes.

Antenatal diagnosis

Prenatal diagnosis is possible using cytogenetic tools.

Genetic counseling

The risk of recurrence for siblings depends on the parental karyotypes.

Management and treatment

Management is multidisciplinary and symptomatic only. Early educational (speech, occupational and physical therapy) and rehabilitation programs should be offered to all patients.

Prognosis

Prognosis is variable. A number of reported patients died in infancy from respiratory problems.