pediatrics
Trisomy 13
Introduction
Trisomy 13 is caused by an extra chromosome 13 and causes abnormal forebrain, midface, and eye development; severe intellectual disability; heart defects; and small birth size. Diagnosis is with cytogenetic testing. Treatment is supportive. (See also Overview of Chromosomal Abnormalities .) Trisomy 13 occurs in approximately 1.7/10,000 pregnancies (based on data from induced abortion for fetal anomalies, stillbirths, and live births) ( General reference ); approximately 80% of cases are complete trisomy 13. Advanced maternal age increases the likelihood, and the extra chromosome is usually maternally derived. Infants tend to be Small-for-Gestational-Age (SGA) Infant . Midline anomalies are common and include The ears are abnormally shaped and usually low-set. Hearing loss is common. Scalp defects and dermal sinuses are also common. Loose folds of skin often are present over the back of the neck. A single transverse palmar crease, Polydactyly , and hyperconvex narrow fingernails are also common. Approximately 80% of cases have severe Genitals are frequently abnormal in both sexes; Cryptorchidism and an abnormal scrotum occur in boys, and a bicornuate uterus occurs in girls. Apneic spells in early infancy are frequent. Intellectual Disability is severe. 