Diagnostic ultrasound ( PDFDrive )

1388 PART IV Obstetric and Fetal Sonography
A
B
C
D
FIG. 40.11 Thanatophoric Dysplasia at 22 Weeks. (A) Proile; midface hypoplasia with lat nasal bridge. (B) Sagittal sonogram shows disproportionately
narrow thorax and relatively protuberant abdomen, signifying lethal condition on the basis of pulmonary hypoplasia. (C) Short curved
femur (calipers). (D) Sparing of foot length versus extreme shortening of tibia. (Courtesy of Fetal Assessment Unit, University Health Network.)
Sonographic Assessment of Bones—cont’d
Bell-shaped thorax of pulmonary hypoplasia
Convex contour in cross section
HANDS AND FEET
Postural deformities
Abnormal number of digits
Syndactyly
CALVARIUM
Macrocranium
Frontal bossing
Craniosynostosis
Compressibility/abnormal degree of mineralization
FACIAL FEATURES
Cleft lip and palate
Hypertelorism and hypotelorism
Midface hypoplasia/lat nasal bridge
Langer et al. 56 distinguished two types of thanatophoric
dysplasia. he more common type 1 (TD1), usually caused by
the R248C and Y373C mutations in the FGFR3 gene, displays
the typical “telephone receiver” shape of the femurs 57,58 (see Fig.
40.2H). his bowed or curved appearance is secondary to the
broadened metaphyses at the ends of the severely shortened
tubular bones. TD1 is associated with frontal bossing and a
lattened nasal bridge with midface hypoplasia. Occasionally,
craniosynostosis results in a mild variant of cloverleaf skull
deformity. Platyspondyly is present. In type 2 (TD2), usually
caused by the K650E mutation in the FGFR3 gene, the femurs
are typically straight with lared metaphyses and the skull has a
cloverleaf or trilobed appearance in the coronal plane that results
from premature craniosynostosis of the lambdoid and coronal
sutures (Fig. 40.12). Other conditions that may be associated
with this unusual skull deformity are homozygous achondroplasia,
campomelic dysplasia, and trisomy 13. Both TD1 and
TD2 are autosomal dominant conditions, with all cases caused
by new mutations in the FGFR3 gene. FGFR gene mutations are