Diagnostic ultrasound ( PDFDrive )

1396 PART IV Obstetric and Fetal Sonography
A
B
C
FIG. 40.22 Campomelic Dysplasia at 27 Weeks. (A)
Shortened femur and tibia with ventral bowing. (B) Radiograph
conirms ventral bowing of the shortened tibia and femur. (C)
Short and curved dysplastic scapula (calipers).
Ellis–van Creveld syndrome (Fig. 40.23A, B, and E) and
asphyxiating thoracic dystrophy have similar features, but the
shortening of the limbs and the narrowing of the thorax are less
severe.
he short-rib polydactyly syndromes or short-rib thoracic
dysplasia with or without polydactyly consists of multiple types:
Type 1 (Saldino-Noonan) and type 3 (Verma-Naumof)
syndromes are caused by mutations in the DYNC2H1 gene
(dynein, cytoplasmic 2, heavy chain 1) and IFT80 gene (intralagellar
transport 80). Type 2 (Majewski or SRTD6) is caused by
mutation in the DYNC2H1 and NEK1 genes. Type 4 (Beemer-
Langer) can occur without polydactyly. 73,76 Type 5 is caused by
homozygous or compound heterozygous mutations in the WDR35
gene. Radiographic and clinical features can distinguish them. 73,76
Fibrochondrogenesis is a rare, usually fatal condition and
survivors sufer from severe physical and neurologic impairment.
It is autosomal recessive rhizomelic chondrodysplasia caused by
a homozygous mutation or compound heterozygous mutations
in the COL11A1 and COL11A2 genes. he typical features include
narrow chest (short ribs with cupping), short long bones with
irregular metaphyses with peripheral spurs, and extraarticular
calciications giving the appearance of stippling, platyspondyly
with decreased ossiication (particularly cervical vertebrae), and
vertebral midline clets. Other features include lat facies and
clet palate. 77,78
Other Dysplasias
Other lethal skeletal dysplasias include atelosteogenesis, boomerang
dysplasia, de la Chapelle dysplasia, and Schneckenbecken
dysplasia. hese dysplasias are rare and diicult to diagnose
prenatally.
NONLETHAL OR VARIABLE-
PROGNOSIS SKELETAL DYSPLASIAS
he nonlethal or variable-prognosis skeletal dysplasias form a
larger group typically presenting with milder and later onset of
skeletal abnormalities. Select nonlethal or variable-prognosis
skeletal dysplasias with characteristic ultrasound indings are
described in Tables 40.6, 40.7, and 40.8.
Heterozygous Achondroplasia
Heterozygous achondroplasia is known to be associated with
the c.1138G>A (p.Gly380Arg) gene in about 98% of the cases
and the c.1138G>C (p.Gly380Arg) mutation in about 1% of the
cases. he FGFR3 gene is also associated with isolated craniosynostosis,
thanatophoric dysplasia, and some cases of hypochondroplasia.
58,60 he identiication of the gene and gene
mutations associated with achondroplasia has allowed preimplantation
genetic diagnosis as well as prenatal diagnosis, using
DNA analysis, when the parents are heterozygous for
achondroplasia. 60
Heterozygous achondroplasia is the most common nonlethal
skeletal dysplasia. 5 About 80% of cases are the result of a spontaneous
autosomal dominant mutation associated with advanced
paternal age, and the remainder are inherited from parental
heterozygous achondroplasia. he incidence is 1 in 26,000 births.