Trisomy 8

Complete Trisomy 8 occurs in 0.8% of spontaneous pregnancy losses. Mosaic trisomy 8 is a well-known syndrome characterized by severe mental retardation, craniofacial dysmorphism, skeletal anomalies, complex congenital heart defect, and kidney malformations.

(Figure)

Trisomy C; Trisomy 8s.

Mosaicism is less common than what is often referred to as “full” trisomy. A mosaic exists when a person presents with trisomic cells in their body, but in the presence of normal chromosomic cells. The genetic error occurs during the division of cells after fertilization. Trisomy 8 is rarely observed at birth.

Clinically evocated; patients with trisomy 8 mosaicism present with moderate mental retardation, multiple skeletal anomalies, urogenital malformations, congenital heart defects, deep palmar and plantar furrows, distinct facial dysmorphism, and agenesis of the corpus callosum.

Clinical features involve head and face (simian crease seizures; expressionless facies; micrognathia; prominent forehead; large dysplastic ears; microphthalmia; strabismus; hypertelorism; corneal opacity; cataract, heterochromia; everted lips; highly arched or cleft palate and stretched) and skeleton (short neck; thin, elongated trunk; pectus carinatum; camptodactyly; clinodactyly; short metacarpal and metatarsal bones; absent or dysplastic patellae; multiple joint contractures; coxa valga; abnormal diaphyses and epiphyses of radial, femoral, and humeral bone; kyphoscoliosis, hemivertebrae; fusion of vertebrae; spina bifida; broad dorsal ribs). Abdominal and pelvic organs (hydronephrosis, ureteral reflux, cryptorchidism, malrotation or absence of gallbladder, jejunal duplication, gastric sarcoma) and thoracic organs (cardiac septal defects and great vessel anomalies) can present malformations. Deep palmar and plantar furrows are frequent.

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

Careful intraoperative positioning should be done (vertebral anomalies, joint contractures). Direct laryngoscopy and tracheal intubation can be difficult because of short neck and microretrognathia. Spontaneous respiration must be maintained at all times because face-mask fit may be difficult, and failure to intubate the trachea highly possible. The availability of a laryngeal mask airway and/or fiberoptic equipments is highly recommended. Venous access can be difficult because of limb anomalies. Perimedullar anesthesia is often contraindicated or difficult because of vertebral and spine anomalies.

Consider anesthetic drug interaction with antiepileptic medications. Prophylactic antibiotics should be as indicated in case of cardiac defect. Preserve spontaneous ventilation before intubation is performed. Avoid anesthetic drugs with marked cardiovascular effect.

Trisomy 8p: Duplication 8p with craniofacial defects, brevicollis with redundant skin folds, and mental retardation. High, prominent forehead; wide face in infancy; fleshy, everted lower lip; long and poorly defined philtrum with marked macrostomia and gingival hypertrophy; low nasal bridge and antevertebral nostrils; hyperextensibility of the finger joints; and hypoplastic nails. Cardiac malformations (33% of patients) are reported. Agenesis of the corpus callosum with severe epilepsy, spina bifida occulta, and numerous genitourinary anomalies. Phenotypic expression is related to the length of the duplicated segment.

Trisomy 8q: Low birth weight, mental deficiency, prominent forehead, flat occiput, hypertelorism, up-slanting palpebral fissures, ear and nose deformities, thin upper lips, and skeletal defects.