Module 7 : Skeletal Dysplasia Flashcards
when does endochondral ossification begin in the fetus
- 10 menstrual weeks
what are the first bones that begin to ossify
- mandible and maxilla @ 8-10 weeks
- ## then calvicle
what is the secondary epiphyseal ossification centre of
- distal femur
- distal humerus
what is the growth rate of the femur until 27 weeks
- 3mm/week
what is the growth rate of the femur from 28 weeks to term
- 1mm/week
what are 4 indications for skeletal dysplasia
- specific genetic risk
- apparent limb abnormality
- associated abnormality
- abnormal amniotic fluid level
what are the 3 errors of morphogenesis
- malformation
- deformation
- disruption
what is malformation and what are the 2 causes
- abnormal formation of tissue
- genetic, teratogenic
what is deformation and what is the cause
- normally developed but abnormal force alters structure or shape
- oligo
what is disruption and what are the 2 causes
- normally developed but abnormal interference causes tissue destruction
- vascular occlusion = limb reduction
- tering amniotic membrane = tissue destruction
what are 4 different patterns of shortening
- rhizomelia
- mesomelia
- micromelia
- acromelia
what is rhizomelia
- proximal portion of limb is shortened
- femur and humerus
what is mesomelia
- middle portion of the limb is shortened
- radia/ulna and tib/fib
what is micromelia
- all portions of limb shortened
what is acromelia
- distal portion of limb shortened
- hands and feet
what is phocomelia
- absence of the proximal portion of the extremity
- hands or feet attached to the trunk of the body
how many standard deviations below normal should we follow up
- 2-4SD
do normal length s in the 2nd trimester exclude dwarf syndrome
- no
what the the normal femur length/abdominal circumference
< 0.16
what should the femur measure at 18 weeks
- 2.5cm
what are three common lethal skeletal dysplasia
- thanatophoric dysplasia
- achondrogenesis
- osteogenesis imperfecta II
what are 3 rare lethal skeletal dysplasia
- congenital hypophospatasia
- camptomelic dysplasia
- homozygous achondroplasia
when are skeletal dysplasia considered lethal
- severe micromelia (all bones shortened)
- decrease thoracic circumference (pulmonary hypoplasia)
what are 2 factors that warrant extensive screening of targeted areas
- family history
- consanguinity (couples that are relatives)
what is the most common skeletal dysplasia
- thantophoric dysplasia
what do most fetus present with when having Thanato dysplasia
- LGA due to poly
what mutation causes Thanato dysplasia
- mutation of FGR3
what are the general abnormalities of Thanato dysplasia
- MICROMELIA
- CLOVER LEAF SKULL (KLEEBLATTSCHADEL)
- NARROW THORAX
- PLATYSPONDYLY ( flatness of vertebral body)
which type of TD is most common
- type 1
what are the characteristics of TD type 1
- extreme rhizomelia
- bowed bones
- normal trunk length
- platyspondyly
- frontal bossing
what are the characteristics of TD type 2
- straighter long bones
- taller vertebral bodies
- KLEEBLATTSHADEL
what criteria determines if platyspondyly is present
- vertebral bodies are smaller or equal to the intervertebral space
what is the second most common lethal dwarfism
- achondrogenesis
what is achondrogenesis caused by
- decreased mineralization
- autosomal recessive
- parents often relative
which type fo achondrogenesis is more severe and less common
- Type 1
- abnormal cranial and spinal ossification
what is the less severe more common type of achondrogenesis
- type II
- abnormal vertebral body ossifications
- normal cranium
what are the sonographic features of achondrogenesis
- MICROMELIA
- SMALL THORAX
- DECREASES MINERALIZATION OF BONES
- FRACTURES AND BOWING OF LIMBS
- MAY HAVE SEVERE HYDROPS
what is osteogenesis imperfecta
- autosomal dominant or recessive
- defective collagen
what are the types of osteogenesis imperfecta and which ones are lethal
- lethal = type IIA
- mild = type I, II, IV
what are the characteristics of osteogenesis imperfecta type IIA
- severe micromelia
- thickeneing along bones from fractures
- accordion bones
- hypo mineralization of bone
- rib fractures
- platyspondyly
what is congenital hypophosphatasia
- autosomal recessive disease
- abnormal bone mineralization
what are 4 features of congenital hypophosphatasia
- variable micromelia
- diffuse hypomineralization
- bones are thinned, delicate, or absent
- +/- fractures
what is another name for camptomelic dysplasia
- bent bone dysplasia
what are 4 common features of camptomelic dysplasia
- bowing of most long bones
- severe talipes equinovarus
- absent/hypoplastic fibulae
- narrow thorax
what must occur for homozygous achondroplasia to happen
- one parent must be affected but usually its both parents
what are the characteristics of homozygous achondroplasia
- rhizomelia
- small thorax
- large cranium
what are 3 non lethal skeletal abnormalities
- heterozygous achondroplasia
- asphyxiating thoracic dysplasia
- dystrophic dysplasia
what are the features of heterozygous achondroplasia
- MODERATE RHIZOMELIA
- NOTICED 3RD TRI
- NORMAL THORAX
- large calvarium
- frontal bossing
what is the most common non lethal dysplasia
- heterozygous achondroplasia
what are the features of asphyxiating thoracic dysplasia
- moderate rhizomelia
- thorax long and narrow
- cystic renal dysplaisa
- polydactyl
what is another name for ellis-van creveld syndrome
- chondroectodermal dysplasia
what are the features of ellis-van creveld syndrome
- short limbs
- short ribs
- carrot thorax
- polydactyl
- dysplastic nails and teeth
- upper lip abnormalities
- congenital heart disease
what is aase syndrome
- AR
- underdevelopment of bone marrow causing anemia
- severe cases will be still born
what re the features of aase syndrome
- congenital limb contracutres
- cleft palate
- ear deformities
- droopy eyelids
what is holt-oram syndrome
- AD
- skeletal and cardiac abnormalities
what are the skeletal and cardiac abnormalities from holt Oram syndrome
- upper limb abnormalities \+ tri[halangeal thumb \+ phocomelia \+ radial ray syndrome - cardiac defects determine the severity of outcome
what is TAR syndrome
- thrombocytopenia-absent radius syndrome
- bilateral absent radii
what is radial ray syndrome
- absent or hypoplastic radius
- holt oram
- Robert phocomelia
- VACTERL
what is talipes equinovarus
- club foot
- chromosomal NTD skeletal or decreased fluid
what is rocker bottom foot
- absent arch due to large calcaneus bone
what are 7 focal limb abnormalities
- polydactyly
- oligodactyly
- syndactyly
- brachydactyly
- clinodactyly
- hitch hikers thumb
what is clinodactyly
- missing middle phalanx
what is syndactyly
- fused fingers
polydactyly
- extra fingers
what is talipomanus
- club hand
what is Amelia
- absence of one or more limbs
what is hemimelia
- absence of oner or more extremities below the elbow or knee
what is acheria
- absence of one or more hands
what is apodia
- absence of one or more feet
what is adactyly
- absence of one or more digits from the hands or feet
what is meromelia
- absence of part of a limb
what is ectrodactyly
- split hand or split foot
what is amniotic band syndrome
- results from 1st trimester rupture of amnion
what 3 things does ABS result in
- constriction
- clefting
- amputation
what should we asses with ?dysplasia
- length of all bones including clavicle
- shape contour and density of al bones
- spine
- thoracic circumference and shape as well as cardiac circumference
- hands and feet
- skull and face
- skin folds
- amniotic fluid
why should we measure foot length
- fetal foot more accurate measurement for gestational age in the case of skeletal displace
if the thorax seems abnormally small then what dysplasias should we considered
- achondrogenesis
- homozygous achondroplasia
- osteogenesis imperfecta
- thantophoric dwarfism
- hypophospatasia
what four things can help us determine if a skeletal dysplasia is lethal or non lethal
- severe micromelia
- decrease thorax circumference
- long bone fractures
- kleeblattshadel
