Genetics for Nurses in Obstetric Disciplines A guide to recognition and referral of congenital and genetic disorders AUTHORS: Golder N. Wilson MD PhD, 1 Vijay Tonk PhD, 2 REVIEWERS Shirley Karr BSN RN, 3 Joanna K. Spahis BSN CNS, 4 Shirley Myers, 5 RNC, MSN, FNP, and Sherry Letalian RN 6
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A guide to recognition and referral of congenital and genetic disorders
Golder N. Wilson MD PhD,1 Vijay Tonk PhD,2
Shirley Karr BSN RN,3 Joanna K. Spahis BSN CNS,4 Shirley Myers,5 RNC, MSN, FNP, and Sherry Letalian RN6
1Clinical Professor of Pediatrics, Texas Tech University Health Science Center at Lubbock and Private Practitioner, KinderGenome Genetics, Dallas Texas; 2Professor of Pediatrics and Obstetrics-Gynecology; Director, Cytogenetics Laboratory, Texas Tech University Health Science Center at Lubbock;3Genetics Coordinator, Maternal-Fetal Medicine and Genetics, Texas Tech University Health Sciences Center at Amarillo;4Pediatric Clinical Nurse Specialist in Genetics and Coordinator of the Down Syndrome Clinic, Department of Genetics, Children’s Medical Center of Dallas5Women’s Health Nurse Practitioner, Maternal-Fetal Medicine and Genetics, Texas Tech University Health Sciences Center at Amarillo;6Pediatric Clinic Coordinator, Department of Pediatrics, Texas Tech University Health Sciences Center, Lubbock
This presentation was designed as part of the GEN-ARM (Genetics Education Network for Nursing Assessment, Recognition, and Management) for the Mountain States Region Genetics Collaborative (MSRGCC); contact www.mostgene.org or Ms. Joyce Hooker at firstname.lastname@example.org
Genetic diseases affect 5-10% of children
Nurses can recognize and refer genetic disorders without need for esoteric genetic knowledge
We will now present cases where your nursing skills and alertness (REYDAR=Recognize, EYDentify, Assess, Refer) can greatly benefit children with genetic diseases.
These cases will introduce you to simple principles of genetics that will give you confidence in recognizing these patients and foster a medical home
These cases and principles are geared to the nursing genetics primer and resources on the GENARM CD
Newborn with large head and deformed bones with fractures by x-ray
The family history indicated that the mother and other relatives had mild features of osteogenesis imperfecta or brittle bone disease (see Chapter 2)
Suspicion of genetic disease underlying this unusual infant led to referral and genetic counseling for this autosomal dominant disease—mother’s guilt about her accident was assuaged and she learned she had a 50% chance each of her future children would have OI
Categories of genetic disease relate to the steps from gene to family (genetic hierarchy)
Sickle cell anemia can be predicted (25% risk for next child) and tested (abnormal S protein or gene)
Other inherited anemias can be related to different abnormal globin alleles (C, D, E, thassemias).
A or S
Mendelian diseases reflect transmission of single genes (abnormal alleles) = DNA diagnosis
Multifactorial diseases reflect multiple abnormal genes plus environment = DNA/HLA markers
Many genes altering development cause isolated birth defects like cleft palate
Many genes altering enzyme pathways cause common metabolic diseases
(e.g., adult-onset diabetes, hyperlipidemia)
Many genes altering organ function(s) produce adult diseases (e.g., schizophrenia)
Chromosomal diseases imbalance multiple genes and cause multiple birth defects = Karyotype
Recognition → Category → Referral ↔ Medical home
(see Chapter 1)
Case 9P. Adolescent female with unplanned pregnancyA 16-year-old female was referred to obstetric clinic from the emergency room after a diagnosis of malnutrition and a positive pregnancy test. She had been brought in by the police for vagrancy and alcoholism, exhibiting poor hygiene and nutrition on examination. Fetal ultrasound revealed a fetus of about 3 months gestation with very small head circumference, abnormal head shape, and intrauterine growth retardation. Her obstetric RN recognized two likely diagnoses, and referred her to maternal-fetal medicine for evaluation including level II ultrasound.
REYDAR of common obstetric presentations
Recognition category referral and management
Case 9P (cont): The intrauterine growth retardation and small head circumference would be consistent with fetal alcohol syndrome. However, the unusual head shape and severe microcephaly by ultrasound raised the possibility that the fetus had anencephaly (OMIM #206500, others). Had this young female remained in pediatric care, she could have benefited from counseling regarding the importance of preconception/prenatal care. Preconceptional supplementation of folic acid can reduce the incidence of neural tube defects like anencephaly or spina bifida by 2/3. It is likely that this young woman had poor nutrition with low folic acid as part of her street lifestyle and alcoholism.. Recognition of her social history was the key to REYDAR, not knowledge of a rare disease.
A 26-year-old Caucasian woman with no chronic illnesses presents to an obstetric nurse practitioner for her initial prenatal visit. Her last menstrual period was three weeks ago and a home pregnancy test was positive. She has no prior miscarriages or infertility and her family history is normal. Her husband is also age 26, Caucasian, and in good health with a normal family history. What general risks and tests should the nurse consider for this pregnancy and what precautions should be mentioned regarding significance of the test results?
Cloned DNA segment
from target chromosome
13, X, Y
No culture or need for
Now a rapid FISH test is available that does not require stimulation of cell division and gives results within 2-4 hours. Rapid FISH highlights chromosomes commonly involved in disorders—e.g., 13 (Patau syndrome), 18 (Edwards syndrome), or 21 (Down syndrome), showing three versus the normal two FISH signals in each cell nucleus (X and Y probes also show Turner syndrome ordocument sex in cases of ambiguous genitalia)
Complementing chromosome analysis is DNA technology that allows screening for common mutations in certain ethnic groups—e. g., cystic fibrosis (OMIM #219700) for Caucasians, hemoglobinopathies (e.g., sickle cell anemia-- OMIM #603903) for Africans or Asians, Tay-Sachs disease (OMIM #272800) for Jews. Cystic fibrosis has an incidence of about 1 in 1600 Caucasion infants, with a 1 in 20 chance that the average Caucasian parent will be a carrier. The nurse can inform her Caucasian patient of cystic fibrosis screening but also discuss the consequences of a positive result—testing the husband to see if he too is a carrier, then considering amniocentesis to test fetal DNA for the 1 in 4 chance the fetus will have cystic fibrosis. Although DNA testing is highly accurate, rare cystic fibrosis mutations that confer mild disease and composite mutations (compound heterozygotes) can limit predictions of putative disease severity in the fetus. Women should also be informed that DNA analysis may reveal non-paternity.
See Chapter 7 for more information
Case 13P: Couple with maternal history of mental retardation
Bob and June present to a nurse practitioner for prenatal care at an estimated 6 weeks of pregnancy. Bob is 26, June 24, and they had a normal daughter Karen two years ago with no pregnancy or delivery problems. Both are healthy and of Caucasian ancestry, and Bob’s family history is normal The nurse finds that June is an only child, but that her mother Gail has two brothers who have mental retardation. In addition, Gail has a sister Joan with with two boys and a girl, and one boy Eric has mental retardation thought due to birth injury. Gail’s other sister Jill has three boys and two girls, and her eldest son Jim has mental retardation of unknown cause. One of Jill’s daughters has also had learning problems that caused her to drop out of high school, and she has a preschool son Bert with speech delay. What concerns should the nurse address?
Case 13P: Discussion
Besides the usual options for genetic and fetal screening (ultrasound, quad screen, cystic fibrosis screening), the nurse should recognize the positive family history and recommend genetic evaluation. The presence of several relatives with the same condition (mental disability) brings up the possibility of Mendelian disease, and sketching of the family pedigree (below) would suggest an X-linked disorder associated with mental retardation. Genetic evaluation would inform June that her mother Gail has a 50% chance and she a 25% chance to be a carrier for the X-linked disease.
The X-linked fragile X syndrome (OMIM #300624) is the most common genetic cause of mental disability with an estimated incidence of 1 in 2000 males. Since June is early in her pregnancy, a fragile X DNA test could be performed on one of her male relatives to confirm or exclude this diagnosis. It would be ideal if one of her affected male relatives could be evaluated by a clinical geneticist so that the diagnosis of fragile X syndrome or another of the >20 syndromes associated with X-linked mental disability could be suspected.
Table 4.1. Multifactorial Disorders in the United States
*Ranks first for neonatal causes of death; approximate scale: ++++ (100% of predisposition due
to genetic factors as for Mendelian disorders) to + (20% of predisposition due to genetic factors)
Multifactorial disorders: For some (e.g., coronary artery disease), single genes of major effect (e.g., those regulating cholesterol) are good risk markers)
Recognizing at-risk children or adolescent females provides important opportunities for nursing education and prevention (see chapter 4)