Module 10: Fetal Skeletal Dysplasia's Flashcards
When does endochondral ossification begin?
10 menstrual weeks
When do the mandible and maxilla ossify?
8 to 10 menstrual weeks
When does the clavicle ossify?
After the mandible and maxilla
ALL long bones ossify by the end of when?
1st trimester
Secondary epiphyseal ossification of the distal femur should occur when?
32 weeks or greater
Secondary epiphyseal ossification of the distal humerus should occur by?
> 38 weeks
What may delay the progression of the secondary epiphyseal ossification center?
IUGR
What is the femoral growth rate until 27 weeks?
3 mm/wk
What is the femoral growth rate from 28 weeks until term?
1 mm/wk
What are four indications for skeletal dysplasia?
Specific genetic risk, apparent limb abnormality, associated abnormality, abnormal amniotic fluid level
What are the three errors of morphogenesis?
Malformation, deformation, and disruption
What does malformation mean in terms of errors of morphogenesis?
Abnormal formation of tissue (could be genetic or due to maternal drug use)
What does deformation mean in terms of errors of morphogenesis?
Normally developed, but abnormal force alters structure shape
What is something that could cause deformation?
Oligohydramnios
What does disruption mean in terms of errors of morphogenesis?
Normally developed, but abnormal interference causes tissue destruction
What are some examples of disruption?
Vascular occlusion (limb reduction), and tearing (amniotic bands) causing tissue destruction
What are the five patterns of shortening?
Rhizomelia, mesomelia, acromelia, micromelia, and phocomelia
What is rhizomelia?
Shortening of the proximal portion of limbs
What is mesomelia?
Shortening of the middle portion of limbs
What is acromelia?
Shortening of the distal portion of limbs
What is micromelia?
Shortening of all portions of limbs
What is phocomelia?
Shortening of the hands and feet attached to the body
How many standard deviations are shortened bones?
> 4
What kind of follow up would a 2-4 SD require?
Follow up in 2-4 weeks to ensure normal growth
Which dysplasia’s have a better diagnosis?
Ones that manifest later with less severe features
What should the femur measure at 18 weeks?
2.5 cm
What comparison can help assist in the diagnosis of a skeletal dysplasia?
Comparison of the long bones to fetal feet
Lethal skeletal dysplasias can be what two things?
Sporadic dominant or AR inheritance pattern
What are three common lethal skeletal dysplasias?
Thanatophoric dysplasia, achondrogenesis, osteogenesis imperfecta II
What are three rare lethal skeletal dysplasias?
Congenital hypophosphatasia, camptomelic dysplasia, homozygous achondroplasia
What percentage of common lethal dysplasias are either thanatophoric or achondrogenesis?
60%
When is a dysplasia considered lethal?
Severe micromelia, decreased thoracic circumference, pulmonary hypoplasia
If you see ‘consanguinity’ on a req, what does it mean?
Couple are relatives (AR traits more prevalent)
What is the most common skeletal dysplasia?
Thanatophoric dysplasia
Thanatophoric dysplasia is a mutation of what?
FGFR3 (fibroblast growth factor receptor 3)
What are the lethal features of thanatophoric dysplasia?
Micromelia, Kleeblattschadel (clover-leaf skull), narrow throax, and platyspondyly
Which type of TD is most common?
Type I
What does Type I TD include?
Extreme rhizomelia, bowed bones, normal trunk length, platyspondyly, and frontal bossing
What does Type II TD include?
Straighter long bones, taller vertebral bodies, and Kleeblattshadel
In what plane can Type II Kleeblattschadel be seen best?
Through the axial planes of the fetal brain
What should the femur to foot ratio be in a normal fetus?
1
What does platyspondyly describe?
Thin vertebral bodies with thick intervertebral spaces
What can a narrow chest be referred to as?
Bell shaped chest
What is seen with achondrogenesis?
Decreased mineralization
Is achondrogenesis dominant or recessive?
Autosomal recessive (parents are often relatives)
Which type of achondrogenesis is most common at what percent?
Type II at 80%
Which type of achondrogenesis is more severe?
Type I
What is the main difference between the lethality’s of Type I and II achondrogenesis?
Type I has abnormal cranial ossification while Type II has a normal cranium
What are the sonographic features of achondrogenesis?
Micromelia, small throax, decreased mineralization, fractures and bowing of limbs, and may have severe hydrops
Osteogenesis imperfecta describes defective what?
Collagen
Which type of osteogenesis imperfecta is most common?
IIA at 80% and is lethal
Which types of osteogenesis imperfecta are considered mild?
I, III, and IV
What are examples of rare lethal skeletal dysplasias?
Congenital hypophosphatasia, camptomelic dysplasia, homozygous achondroplasia
What is congenital hypophosphatasia?
Autosomal recessive abnormality that is characterized by abnormal bone mineralization due to alkaline phosphatase deficiency
What can congenital hypophasphatasia mimic?
OI IIA
Camptomelic dysplasia is also known as what?
Bent bone dysplasia
What are features of comptomelic dysplasia?
Bowing of most long bones, club feet, absent or hypoplastic fibulae, narrow thorax
What are examples of non-lethal skeletal abnormalities?
Heterozygous achondroplasia, asphyxiating thoracic dysplasia, and diastrophic dysplasia
What are the features of heterozygous achondroplasia?
Moderate rhizomelia, large calvarium, frontal bossing, and normal thorax
What is the most common non-lethal dysplasia?
Heterozygous achondroplasia
What is asphyxiating thoracic dysplasia?
Moderate rhizomelia, long and narrow thorax, cystic renal dysplasia, and polydactyly
What is another name for club foot?
Talipes equinovarus
