Prenatal
Mom was referred for a genetic consultation due to a thickened nuchal fold
and abnormal positioning of hands and feet seen in today's ultrasound. She
reports no exposure to medications, cigarettes, alcohol, drugs, chemicals, or
radiation. She is currently 21 weeks 4 days gestation with an estimated
delivery date of August 2002. The pregnancy has been uncomplicated thus
far. Mom will be 25 years of age at time of delivery.
The family history is negative for birth defects, mental retardation or other
genetic disorders.
Today's ultrasound detected abnormal positioning of the limbs characterized by
extended arms with flexion of hands and wrists (policeman tip" hands) and
inferior extension of the feet. We explained that this finding may be
occurring as an isolated event or it may be indicative of a specific genetic
condition or neurologic abnormality. For instance, Amyoplasia
Congenita Disruptive Sequency is a condition that is characterized by similar
limb findings. This sequence occurs sporadically and is often caused by an
intrauterine vascular accident. Unfortunately, it will be difficult to
confirm a diagnosis or predict the significance of this finding prenatally.
Therefore, the baby will be seen for a genetic consult after delivery.
The ultrasound also detected a thickened nuchal fold, or extra thickness around the back of the baby's neck. This accumulation of fluid can be seen in normal pregnancies, but it can also be associated with decreased fetal movement and or chromosome conditions. The most common chromosome abnormality seen in pregnancies with a thickened nuchal fold is Down Syndrome, or Trisomy 21. The risk for Down syndrome in a pregnancy with thickened nuchal fold is 1 in 57 or 2 % for a 25 year old woman. Down syndrome is the result of having three copies of the # 21 chromosome rather than the expected two copies. This can cause such problems as mild to moderate mental retardation, heart defects, and characteristic facial features.
Another screening test routinely offered to all women during pregnancy is maternal serum screening, or AFP analysis. This is a blood test performed at 15-20 weeks gestation which screens for neural tube defects, Down syndrome , and Trisomy 18. Maternal serum screening identifies approximately 90% of neural tube defects. Coupled with ultrasound, the detection rate increases to approximately 95%. Serum screening identifies 60% of pregnancies with Down syndrome and 60-70% of pregnancies with Trisomy 18. Ani reports that the results of her maternal serum screen were normal.
Due to the increased risk for a chromosome abnormality seen in pregnancies with a thickened nucal fold, an amniocentesis was offered to Ani today. Amniocentesis is a test that can be used for prenatal diagnosis of fetal chromosome abnormalities and can also diagnose neural tube defects such as spina bifida. Amniocentesis is typically performed beginning at 15 weeks gestation and involves inserting a long tin needle through the abdomen into the amniotic cavity and removing 2-3 tablespoons of fluid. This fluid contains fetal skin cells that are used for chromosome analysis, which is 99.9% accurate. Amniocentesis carries a risk for complications, including miscarriage , of 1/2% or less. Preliminary results from a FISH (florenscence in-situ hybridization) analysis of chromosomes 13, 18, 21, X and Y will be available in approximately 48 hours, but the final results will take 1-2 weeks. After discussing the benefits, risks and limitations of amniocentesis, Ani decided to proceed with testing today. We will contact as soon as these results are available.
There is always a 2-3% chance for birth defects and a 2-3% chance for learning problems in every pregnancy, and unfortunately, not all of these can be detected prenatally. Ample opportunity was given for Ani to ask questions concerning the information presented today. They may contact our office should they have any further questions or concerns. The medical history and family history were reviewed by Dr. **** who agrees with the genetic counseling provided.
ADDENDUM: The results from the FISH analysis reveal an apparently normal pattern for chromosomes 13,18,21,X and Y. We will contact Ani again when the final amniocentesis results are available.
Postnatal
Abby is a 2 day old female seen for initial genetic consultation concerning a prenatal diagnosis of Amyoplasia and postnatally documented positional deformities of her extremities. Her mother, was seen during the pregnancy for genetic counseling. Her OB Dr. had noted a thickened nuchal fold and abnormal positioning of the hands and feet on an ultrasound. Mother was approximately 21 1/2 weeks gestation at the time. Due to the abnormal positioning of the limbs, it is felt that the baby was most likely affected with a condition known as Amyoplasia. At birth the documented findings were as expected from the prenatal ultrasound. An amniocentesis was performed during the pregnancy and revealed a normal karyotype.
Abby is an alert infant who is normocephalic and has a soft anterior fontanel. Ears are normally shaped and positioned. The nasal bridge and nose appear normal. She has a capillary hemangioma present on her nasal tip. The shoulders are rounded and chest wall is narrow. The lungs are clear to auscultation. The heart tones reveal a regular rate and rhythm without murmurs. The spine is straight. The extremities reveal decreased muscle bulk with the elbows extended and the arms internally rotated with flexion of the wrists. The hips and knees are flexed and the feet are clubbed bilaterally.
Abby has Amyoplasia. This is typically a sporadically occurring condition in which children have decreased muscle mass and positional deformities of extremities due to decreased intrauterine movement. The majority of these individual will have normal intellectual development. I will be sending Abby's mom information to read about amyoplasia. She may call me if they have any questions or concerns with which I can help. Abby will be seen for genetics follow-up in 2-3 months. I have encouraged her mom to enroll her for BabyNet services through their county health department and to contact Shriners Hospital for an orthopedic evaluation there.
3 Months
Abigail Vinson is a 3 1/2 month old white female seen today for follow-up
genetic consultation concerning her amyoplasia. She is being followed at
Shriners and has splints for her hand. They are discussing the option of
surgery when she is 12-18 months old. Presumably this will be to lengthen her
heel cords and correct her bilateral club foot. Her development is
proceeding normally. She is receiving Early Intervention services once a
week.
Physical Examination: Abby is a well developed 3 1/2 month old who has a
weight of 9lb 12oz, length of 22 inches, and head circumference of 38cm.
She has decreased muscle mass of the shoulders and upper arms and mild atrophy
of the calf muscles. The arms are internally rotated and hand are held in
a flexed position. The elbows are extended. The knees are slightly
flexed and the feet have a significant equinovarus deformity. Her cranium
appears normal. The anterior fontanel is soft. The eyes reveal a
bilateral red reflex and the extraocular movements are intact. The midface
is well developed. She has a hemangioma present on her nasal tip.
The palate is intact. The mandible is normally formed. The ears are
normally shaped and positioned. The neck is supple. The chest wall
is symmetric. The lungs are clear to auscultation. The heart tones
reveal a regular rate and rhythm without murmurs. The abdomen is soft
without masses or tenderness. The spine is straight. The extremities are as
described previously.
IMPRESSION: Abigail Vinson has amyoplasia. This is a muscular condition that is usually felt to be sporadic in nature and due to some type of vascular compromise or disruption. The risk for recurrence in subsequent in pregnancies should be extremely low for. Abby is being followed appropriately at Shriners Hospital and will be seen for genetics follow-up in approximately nine months when she is a year old. Her mother may call me should she have any questions or concerns with which I can help.
Clinical Geneticist
Genetic Counselor