Mosaiikchimerism

Mosaiikchimerism is a term used in some genetic discussions to describe a person who bears two or more genetically distinct cell populations that arise from a combined pattern of mosaicism and chimerism. The word blends mosaicism, where distinct cell lines originate within a single individual after fertilization, with chimerism, the presence of cell lineages derived from more than one zygote.

The term fuses mosaicism, where a post-zygotic genetic change creates distinct cell lines within a single individual, with chimerism, the presence of cell lineages derived from more than one zygote. Typically, mosaiikchimerism is proposed to occur when cell exchange between developing twins or embryonic fusion introduces a second genome into a developing body, and subsequent post-zygotic mutations further diversify lineages.

Detection relies on genetic profiling across tissues; samples from blood, skin, or organ tissue may reveal discordant genotypes. Methods include single-nucleotide polymorphism arrays, short tandem repeat analysis, and whole-genome sequencing. In humans, strict cases of mosaiikchimerism are rare and mostly discussed in case reports or theoretical discussions rather than established clinical entities. When recognized, it can complicate paternity testing, organ transplantation decisions, and interpretation of genetic tests.

The concept remains debated, and mosaiikchimerism is not universally recognized as a separate diagnostic category. It highlights the continuum between mosaicism and chimerism and underscores the genetic and clinical complexity of cell lineage mixtures. See also mosaicism, chimerism, and twin-twin transfusion considerations.