Ring chromosome 21 and SOD activity of blood cells

A female infant was found to have an abnormal karyotype with mosaicism: 45,XX,-21/46,XX,r(21) (p11.2 q22.3). She showed a slightly decreased level of superoxide dismutase (SOD) activity in erythrocytes, polymorphonuclear and mononuclear leukocytes. The cuprozinc SOD (SOD-1) activity of leukocytes was 70-80% of normal level, while their manganese SOD (SOD-2) activity was within the normal range. The relationship between the chromosomal aberration and the SOD activity is discussed in relation to the gene dosage effect.