The Chromosomes in Heart Disease

THE CONGENITAL chromosomal syndromes are those in which an implied, but unproved, causal relationship exists between microscopically detectable chromosomal aberrations and congenital malformations and biochemical abnormalities. Precise pathogenetic mechanisms giving rise to these congenital defects are unknown, but it is probable that they ultimately derive from the quantitative imbalance imposed by the absence (monosomy) or added presence (trisomy) of either entire chromosomes or fragments thereof.' To date, more than 50 abnormal chromosomal patterns (karyotypes) have been recorded, but the majority may be classified as karyotypic variants of six prototype chromosomal syndromes. These include Turner's gonadal dysgenesis (monosomy XO), Jacob's "superfemale" (triplo-X), Klinefelter's tubular dysgenesis (XXY), Patau's D,trisomy (group 13-15), Edward's El-trisomy (group 16-18), and mongolism or Gl-trisomy (group 21-22). Characteristically, central nervous system disturbances, soft tissue defects, and cardiac malformations occur in most cases of autosomal trisomy. Similar defects may also occur in certain of the sex-chromosomal syndromes, particularly Turner's syndrome and variants thereof. In the El-trisomy syndrome, heart defects are twice as common as in the maternal rubella malformation complex.2 Moreover, evidence has been presented that sug-