NeurometPlus

Incidence

In Europe, the average recorded prevalence of trisomy 13 is 1.57/10,000 births (including livebirths, stillbirths, and terminations of pregnancy following prenatal diagnosis).

Clinical Characteristics

Trisomy 13 Syndrome is a rare chromosomal disorder in which all or a portion of chromosome 13 appears three times (trisomy) rather than twice in cells of the body. In some affected individuals, only a percentage of cells may contain the extra 13th chromosome (mosaicism), whereas other cells contain the normal chromosomal pair. In individuals with Trisomy 13 Syndrome, the range and severity of associated symptoms and findings may depend on the specific location of the duplicated (trisomic) portion of chromosome 1, as well as the percentage of cells containing the abnormality. However, in many affected infants and children, such abnormalities may include developmental delays, profound mental retardation, unusually small eyes (microphthalmia), an abnormal groove in the upper lip (cleft lip), incomplete closure of the roof of the mouth (cleft palate), undescended testes (cryptorchidism) in affected males, and extra (supernumerary) fingers and toes (polydactyly). Additional malformations of the head and facial (craniofacial) area may also be present, such as a relatively small head (microcephaly) with a sloping forehead; a broad, flat nose; widely or too close set eyes (ocular hypo or hypertelorism); vertical skin folds covering the eyes; inner corners (epicanthal folds); scalp defects; and malformed, low-set ears. Affected infants may also have incomplete development of certain regions of the brain (e.g., the forebrain); kidney (renal) malformations; and structural heart (cardiac) defects at birth (congenital). For example, characteristic heart defects may include an abnormal opening in the partition dividing the upper or lower chambers of the heart (atrial or ventricular septal defects) or persistence of the fetal opening between the two major arteries (aorta, pulmonary artery) emerging from the heart (patent ductus arteriosus). Many infants with Trisomy 13 Syndrome fail to grow and gain weight at the expected rate (failure to thrive) and have severe feeding difficulties, diminished muscle tone (hypotonia), and episodes in which there is temporary cessation of spontaneous breathing (apnea). Life-threatening complications may develop during infancy or early childhood. In summary, it is related to the presence of an additional (third) chromosome on an otherwise diploid chromosome 13 with variable abnormalities, most characteristic of which are microcephaly, microphthalmia, hypertelorism, cleft lip or palate, polydactyly, and cardiovascular, genitourinary, and neurological abnormalities. It is one of the most frequent causes of perinatal deaths.

Precipitants

None

Provocation Tests

None

Diagnostic Procedures

Karyotype. Chromosome 13 trisomy.