Prenatal Unit 3: Lecture 2: Rare Trisomy

Trisomy 16

Most common trisomy leading to miscarriage

Mosaic T16:

Fetal growth restriction

Body asymmetry

Hearing loss

—> Confined placental mosaicism

Trisomy 22

“incompatible with life”

Third most common trisomy in early miscarriages

Trisomy 8

incompatible with life

Mosaic:

Prominent forehead small chin, large ears

Cardiac, skeletal, and urogenital anomalies

Somatic mosaicism

mutation/aneuploidy present in some tissues of the embryo but not necessarily the gametes

Germline mosaicism

Mutation/aneuploidy only present in the gametes

Confined placental mosaicism

Mutation/aneuploidy present in the placenta but not the embryo

Post mitotic Mosaicism

mutation arises after conception

Post mitotic mosaicism common in what conditions?

Osteogenesis imperfecta

Neurofibromatosis type 1

Achondroplasia

What is the difference between Mosaics vs Chimeras?

Chimerisms is the presence of two genetically distinct cell lines in an organisms —> acquired through the infusion of allogenic hematopoietic cells, inherited

Examples of Chimeras?

Individual whose fraternal twin died in utero

Women who have had babies

Recipient of bone marrow or other organ transplant