Disorder | Inheritance and gene | Common ultrasound findings |
Monogenic | ||
Noonan syndrome | Autosomal dominant: Most common genes: BRAF, KRAS, MAP2K1, MRAS, NRAS De novo variant: less common Autosomal recessive: LZTR1 variants | Elevated nuchal translucency, CHD 50 to 80% with pulmonary valve stenosis most common, characteristic facies |
Smith Lemli Opitz Syndrome | Autosomal recessive: Disorder of cholesterol synthesis: DHCR7 – 96% mutation, 4% deletion | 2/3 syndactyly, microcephaly, hypospadias multiple major malformations |
Cornelia de Lange Syndrome | Autosomal dominant: new mutation 99% of time; NIPB, SMC1A, HDAC8, SMC3, RAD21 and BRD4 X-linked: HDAC8, SMC1A | Mild to severe FGR, upper limb defects Cardiac septal defects Microcephaly Characteristic facies |
Fanconi anemia | Autosomal recessive: 25 genes known, FANCA 60 to 70% mutation or deletion Autosomal dominant: RAD51 X-linked: FANCB | Skeletal abnormalities – often radius/thumb GU abnormalities, bone marrow failure, low platelets |
Achondroplasia | Autosomal dominant: FGFR3 mutation De novo: if normal parents | Rhizomelic short limbs >4 SD below mean, macrocephaly, frontal bossing trident hand |
Uniparental disomy | ||
Silver-Russell | De novo: Maternal UPD7 Imprinting defect paternal H/19/IGF2 | Severe early FGR, relative macrocephaly |
Aneuploidy | ||
Triploidy (3n = 69) | ||
Diandric | (2n from the father and 1n from the mother) Sporadic | Symmetric FGR, 80% structural abnormalities Cystic large placenta, oligohydramnios Risk for GTN 1 to 2% |
Digynic | (2n from the mother and 1n from the father) Sporadic | Severe FGR, asymmetric Small placenta, oligohydramnios |
Trisomy | Extra chromosome 13/18 most common | |
Duplications/deletions | Multiple described – 7 to 9% of fetuses with FGR | Structural abnormalities |
Confined placental mosaicism | ||
(Observed for every chromosome except 19) | ||
Chromosome 16 | Most common | FGR in 43 to 58%: malformations: 20% Prematurity: 32 to 37%, Preeclampsia: 16 to 24% |
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