Trisomy 9

At a glance

Chromosomal disorder that can occur in a mosaic or nonmosaic expression, in which all major systems are significantly involved. Clinically characterized by failure to thrive, severe intellectual disability, skeletal abnormalities (kyphoscoliosis, joint anomalies), severe gastroesophageal reflux, craniofacial malformations, complex congenital heart defects. Death occurs mostly in infancy or early childhood.

Synonym

Chromosome 9 Trisomy Syndrome.

History

First reported by Rober H. Haslam, Canadian pediatric neurologist, in 1973.

Incidence

Very rare, accounts for 2.4% of spontaneous abortions.

Pathophysiology

Caused by excessive synthesis by an extra chromosome and varies with the characteristic of the trisomy (total or mosaic).

Diagnosis

Clinically evocated by psychomotor retardation and multiple abnormalities of the craniofacial structures, heart, skeletal system, extremities, and other organs; confirm by karyotype studies.

Clinical aspects

This is a severe disease with growth and mental retardation. Death occurs generally in infancy or early childhood although survival into mid-twenties is reported requiring daily care. Clinical features involve all major systems. Cerebral and craniofacial malformations are constant (Dandy-Walker cyst; subependymal cysts; ventricular dilatation of the brain; microcephaly; prominent occiput micrognathia; wide cranial sutures and fontanels; craniosynostosis; facial cleft and cloverleaf skull; short and up-slanting palpebral fissures; microphthalmia; coloboma; corneal clouding; hypertelorism; deeply set eyes; low-set malformed ears; tongue abnormalities; ankyloglossia; cleft lip/palate). Skeleton abnormalities can include kyphoscoliosis, short and webbed neck, hip dislocation, abnormally shaped long bones, limitation of joint movement, short limbs, and dysplasia of hands and feet. Other clinical features include heart (ventricular septal defect, atrial septal defect, patent ductus arteriosus, valve defects, double-outlet right ventricle, persistent left superior vena cava, endocardial fibroelastosis), urogenital system (hydronephrosis, duplication of collecting system, microcystic kidneys, dysplastic kidneys, cryptorchidism, small penis, hypospadias, hypoplastic labia), and skin (deep palmar and plantar creases, hyperconvex nails).

Precautions before anesthesia

Evaluate cardiac function (clinical, echocardiography, ECG), renal function (echography, urea, creatinine, electrolytes), and tracheal intubation (clinical, radiography).

Anesthetic considerations

Direct laryngoscopy and tracheal intubation can be difficult because of short neck, ankyloglossia, and microretrognathia, and may require advanced airway techniques. Spontaneous respiration must be maintained until tracheal intubation is achieved and lung ventilation is confirmed. A laryngeal mask airway and/or fiberoptic equipment should be readily available. Venous access can be difficult as a result of limb anomalies. Careful intraoperative positioning is necessary considering hip dislocation and joint limitation. Pulse oximetry can be difficult because of nail malformation.

Pharmacological implications

Prophylactic antibiotics should be given as indicated in cases of cardiac defects. Preserve spontaneous ventilation before intubation is performed and avoid anesthetic drugs with marked cardiovascular effects.