Trisomy 21
Definition
Also known as Down syndrome. Incidence in general population is about 1:800 live births.
Due to:
1. The presence of an extra chromosome 21.
2. Presence of only the distal half of chromosome 21, band q22 (q22-critical region).
Risk of congenital heart disease is 40-50%.
Pathology
A genetic disorder occuring due to the failure of a pair of chromosomes to separate at meosis. Exponentially related to maternal age.
Clinical Manifestations
Cardiac: cyanosis is common due to the presence of premature vascular disease with right to left shunting. Bulging pericardium may also be present. Most common associated congenital defects are endocardial cushion defect and mitral regurgitation. VSD, TOF, PDA, CoA, AI, and ASD may be present. Also, pulmonary hypertension and CHF are present.
Inadequate alveolarization is found in terminal lung units distal to respiratory bronchioles, total decrease in cross sectional area of vascular bed, pulmonary vascular disease is prevalent.
Non-Cardiac: infants have flat facial profiles, oblique palpebral fissures (eyes), abundant neck skin, exhibit absence of Moro* reflex. Hands are short and broad with shorter, curved forth finger, palmar simian crease, and distal axial triradius (fingerprints). Skin tends to be dry and relatively pale. The inner epicarthic skinfold on the eyes inserts onto lower lid and Brushfield spots (speckled iris) are present. Mouth sometimes turns down, more common in females.
* Moro reflex - defensive reflex where the infant draws its arms across its chest in response to stimuli.
Surgical Intervention
Limited to correction of congenital defects, survival appears to be no more different from other patients with similar defects.
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