Normal developmental differences in different tissues and cell types | Nuclear DNA sequence the same in all cells (not true mosaicism) | Normal |
Mitochondrial heteroplasmy | Nuclear DNA sequence the same in all cells, mitochondrial DNA can differ from cell to cell due to mutations in the mitochondrial DNA and differential distribution (heteroplasmy) | Patient normal or abnormal; may lead to abnormal offspring |
Chromosomal mosaicism | Nuclear DNA differs; usually two different classes due to varying chromosomal complements | Patient normal or abnormal; may lead to abnormal offspring |
Germ line mosaicism (resulting from a de novo mutation in a germ cell) | Nuclear DNA differs; only in germ line cells | Patient normal; may lead to multiple abnormal offspring |
Somatic mosaicism due to de novo mutation (+/− germ line) (resulting from a de novo mutation at a stage during embryogenesis) | Nuclear DNA differs in different tissues and number of cells, depending on stage and site of the de novo mutation | Patient usually abnormal; disease may be milder than expected |
Somatic mosaicism due to reversion (resulting from a mutation that corrects (reverts) a deleterious inherited mutation in some cells) | Nuclear DNA differs in different tissues and cells, depending on stage and site of the reversion | Patient may be abnormal, possibly milder than expected or occasionally normal |