Skeletal dysplasia

How to detect / identify which dysplasia are lethal??Ans;- Short   Femur  length   and prediction   of lethality   in skeletal   dysplasias . Fetuses with skeletal dysplasias in which    all lethal cases  were associated  with a femur  length   abdominal   circumference ratio   of 0.16  . Although   the test detected   lethal cases   with 100 %  sensitivity   few cases   of achondroplasia   were  erroneously  identified   as lethal using this method. A different   approach   has been proposed   which mentions   lethality    in 23 out of 25 cases of skeletal dysplasias with a femur length below the 1^st percentile for gestational   age and   presence of bell shaped  thorax  or decreased  bone echogenicity.

Lung  volumetry by three   dimensional sonography: can it help to identify the lethality of skeletal dysplasia ?? Ans:- . Fetal  lung volumetry by 3D  sonography  has been performed   using two techniques    multiplanar  and VOCAL  . Nomograms for lung volumetry   using 3D  sonography  are available  in the literature  . Both  the 3D   multiplanar   and 3D VOCAL modes    can be used  to measure   fetal lung volumes  an observation   that was  subsequently   . A potential    advantage   of the VOCAL  technique  is the possibility  of obtaining   fine contours of the lungs   which may be   particularly   valuable   when the  outline   of the organ is irregular such as in cases of congenital diaphragmatic   hernia.  In contrast obtaining   lung volume  measurements using the 3D multiplanar technique is faster   taking usually less  than 5 minutes  to perform . Volumes   are best estimated   when datasets are acquired   using a transverses view of the fetal   thorax.  compared volumetric measurements   of the fetal  lungs obtained using   the VOCAL   method with lung   volumes calculated at the time of   autopsy   in 8 cases   of congenital   diaphragmatic hernia   and in 25   control fetuses   without pulmonary   malformation. The mean   relative error   of 3D   sonography  to estimate the actual lung volume was -7.19 % in cases  of congenital diaphragmatic   hernia and -0.72 %  in normal   fetuses . Barros and colleagues   studied   24  fetuses   with skeletal   dysplasia and measured the total   lung volume   using VOCAL   . an   abnormally    reduced lung volume was defined   as below   the 5^th  percentile   for gestational age   . From    18 fetuses diagnosed at birth   with lethal pulmonary    hypoplasia.  83%   had a total   lung volume    below the 5^th  percentile for gestational age. Lung  volume  more accurately   predicted pulmonary   hypoplasia than thoracic circumference   thoracic  circumference / abdominal   circumference ratio   and thoracic area/ cardiac area   ratio .

 Limb biometry   for the  upper   and lower   extremities respectively . cLong bone  biometry has been  used extensively for the prediction   of gestational age. Nomograms for this    purpose    display the distribution of bone   lengths   in relation to gestational    weeks. For the proper use of   these   nomograms  the clinician  must know  the accurate   gestational age   of the fetus. Therefore    patients   at risk for skeletal dysplasias are advised   to seek prenatal   care at an early gestational   age in order to   assess all clinical   estimators    of gestational age. Present    Nomograms of the measurement   of limb biometry   for the upper   and lower   extremities respectively. Comparisons  between  the   limb dimensions   and head circumference can be   used for patients   presenting   with uncertain   gestational age.

 Should we use the cut off value at  1 st    percentile   of limb growth    for gestational    age should  be used for diagnosis ? Or 5 per centile ?? I have no answer, Members opinion please..  The Nomograms and figures    provide the sonographers & clinicians the mean   3rd  and the 97^th  percentiles  of limb biometric parameters .The clinicians should be aware that  approximately   6%   of the general  population   will fall   outside  these boundaries  . Ideally a more stringent      criterion     such as the 1 st    percentile   of limb growth    for gestational    age should  be used for diagnosis . Unfortunately none of  the currently   available nomograms has  been based   on a sufficient  number of patients   to provide an  accurate    discrimination   between the 3ed  and the   1^st  percentiles   . However   most skeletal dysplasias diagnosed in utero or   at birth  are  associated   with dramatic long bone   shortening and under these  circumstances   the precise   boundary used    is not  critical. An    exception    to this is   achondroplasia   in which limb  biometry  is only mildly   affected until the   third trimester    , when abnormal growth  can be detected by examining the slope  of growth  of the femur length . FL shortening may herald  followings:-- The degree   of femur   length shortening can be   used as the initial  step   in distinguishing   among  the five   most common   disorders     1) thanatophoric   dysplasia. 2) OI (osteogenesis imperrfecta) --type   ll   3) achondrogenesis  4) achondroplasia   and 5) hypochonodroplasia   The early  diagnosis   of skeletal dysplasias in  women with previous pregnancies    affected   with skeletal dysplasia is possible  to note  recurrent   cases were identified   during   the first trimester  by the 1) femur   length/ crown rump length ratio  and  2) the femur    length / biparietal diameter ratio. So , early  evaluation of fetal   structures might    be helpful  in the diagnosis   of severe   skeletal dysplasias.

Nomograms  for long   bone with CRL is available too:--Measurements  according to crown   rump length    in a large    population   of normal   fetuses   examined    between 11 and  14  weeks of  gestation   have been published   but still  their   role in the early   assessment    of pregnancies  at risk   for skeletal   dysplasias   remains   to be determined.  Skeletal Dysplasias  characterized  by Rhizomelia , Mesomelia and Micromelia What is platyspondyly ?? Ans:-The most   common spinal    abnormality   seen in skeletal   dysplasias is  platyspondyly which      consists  of flattening  of the vertebrae . Xyphhosis   scoliosis  and coronal   clefting   of vertebral   bodies  have been   also reported.

Types of skeletal defects : Rhizomelia ,Thanatophoric dysplasia

Atelosteogenesis

Chondrodysplasia  punctata

Congenital short   femur

Achondroplasia

Hypochondroplasia

Mesomelia

Mesomelic  dysplasia

Ellis- van Creveld  syndrome

Acromesomelia

Ellis-  van Creveld syndrome

Micromelia

Achondrogenesis

Atelosteogenesis

Short rib-  polydactyly syndrome

Diastrophic  dysplasia

Fibrochondrogenesis

Osteogenesis   imperfect

Kniest  dysplasia

Dyssegmental dysplasia

Roberts syndrome