Mosaicism
Mosaicism happens when a genetic change is present in some cells but not others. This can occur if the change arises after fertilization during early development. Depending on which cells and tissues carry the change, mosaicism can influence symptoms, test results, recurrence risk, and how a condition presents. Sometimes mosaicism is found in a child; sometimes it is found in a parent at a low level.
Why it matters
Mosaicism can affect diagnosis, genetic counseling, and how families understand recurrence risk. It can also explain why symptoms vary from person to person.
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