A congenital anomaly is an anomaly present at birth whatever its cause (hereditary, viral, toxic…).
Trisomy 21 is a constitutional disorder, since it is associated with a particular constitution, in this case a chromosome 21 present in 3 copies.
This constitutional affection can be associated :
– congenital anomalies, malformative or not: heart disease, digestive malformation, congenital cataract…
– medical problems occurring during life: thyroid anomaly, epilepsy, keratoconus…
– to an intellectual deficiency which is constant.
All these manifestations linked to trisomy 21 are not present at birth, they can be revealed later on. This is what justifies the regular monitoring of patients by doctors who know which anomalies to look for at each age of life.