Trisomy 6q

At a glance

Partial Trisomy 6q is an extremely rare chromosomal disorder with affected infants and children demonstrating growth and mental retardation, craniofacial anomalies, a short, webbed neck, and joint contractures.

Synonyms

Chromosome 6, Trisomy 6q2; Distal Trisomy 6q; Duplication 6q; Partial Distal Duplication 6q.

Incidence

Extremely rare. It appears to affect males and females equally. Approximately 30 cases have been reported in the medical literature.

Genetic inheritance

Chromosome 6, partial trisomy 6q is the result of a balanced translocation in one of the parents. The duplicated portion of 6q2 begins between bands 6q21 and 6q26 and may extend to the end (or “terminal”) of chromosome 6q (qter).

Clinical aspects

Craniofacial abnormalities include microcephaly, an abnormally flat face and occiput, an “almond-shaped,” protruding, ocular hypertelorism, and/or downwardly slanting palpebral fissures. Affected individuals may also have a small “bow-shaped” mouth with thin lips, micrognathia, cleft palate, a large, flat nose, malformed ears, and/or thin, arched eyebrows. In some cases, the coronal and sagittal craniosynostosis causing turricephaly has been reported. The neck may be unusually short and wide with abnormal frontolateral webbing, potentially restricting movement of the jaw and neck. The hairline may be abnormally low on the back of the neck (nape). Joint contractures (fingers, wrists, elbows, knees, hips), causing limitation of movement and abnormal postures, are often associated. Polysyndactyly, clubhands and/or clubfeet, scoliosis, reduced diameter of the chest, and widely spaced nipples. Genital abnormalities include, in affected females, hypoplastic labia, and in affected males, micropenis, hypospadias, and cryptorchidism. It may also include cardiac, intestinal, renal, and cerebral abnormalities.

Precautions before anesthesia

Evaluate cardiac function (clinical, echocardiography, ECG) and renal function (echography, urea, creatinine, electrolytes). Anesthesia consultation is indicated to assess the airway and other medical conditions (especially cardiac).

Anesthetic considerations

Careful intraoperative positioning should be done (vertebral anomalies, joint contractures). Direct laryngoscopy and tracheal intubation will be difficult because of short and webbed neck, the presence of micrognathia, a small mouth opening, and retrognathia. Spontaneous respiration must be maintained until the trachea is intubated and lung ventilation is confirmed. Venous access can be difficult because of limb anomalies. Perimedullar anesthesia is often contraindicated or difficult because of vertebral and spine anomalies.

Pharmacological implications

Prophylactic antibiotics should be as indicated in cases of cardiac defects. Preserve spontaneous ventilation before and during laryngoscopy until tracheal intubation is secured. Avoid anesthetic drugs with marked cardiovascular effects.

References