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7 - Terminology of Errors of Morphogenesis
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Summary
MALFORMATION
A malformation is a qualitative, structural end result of a disturbance of embryogenesis leading to a (congenital) defect of an organ, body part, or body region. Such defects can be mild or severe, common or rare. They arise either during blastogenesis (first 4 weeks of development) or during organogenesis (2nd half of embryogenesis, weeks 5-8). Defects of blastogenesis tend to be severe, to be frequently lethal, and to involve several parts of the developing organism sharing a common inductive molecular pathway (polytopic anomalies; i.e., DiGeorge anomaly) (Figure 7.1 and Tables 7.1 to 7.5). Defects of organogenesis tend to involve single structures (monotopic anomalies) – i.e., isolated polydactly, cleft palate, distal hypospadias, etc. Regardless of how mild or common in the population, malformations are never normal. Mild malformations (cleft uvula or xiphisternum, agenesis of palmaris longus muscle or of upper lateral incisors, spina bifida occulta of L5) are common in the population and tend to be dominantly inherited.
Developmental Fields
Developmental (or embryogenic or morphogenetic) fields are the parts of the embryo that react as a unit in response to normal inductive, teratogenic, or mutational causes (Tables 7.6 and 7.7). During early blastogenesis the entire pluripotent embryo is the primary field. A midline, axis formation and the initial events of gastrulation are its most important morphogenetic characteristics. Progenitor fields (Davidson) arise in the primary field and represent upstream expression domains of combinations of molecular inductive systems including transcription factors (e.g., HOX, SOX, TBX genes), growth factors (FGF, BMPs), and secreted morphogens (i.e., SHH).
19 - Genito-Urinary System
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Summary
MALFORMATIONS
Horseshoe Kidney
A horseshoe kidney is a single, midline, horseshoe-shaped kidney.
The kidney is formed by an interaction between the ureteric bud and the metanephric blastema (Figures 19.1 to 19.3). If the ureteric buds are located more medially than normal or if the inducible metanephric blastema is continuous at the lower pole, then a fused horseshoe kidney may develop.
The horseshoe kidney is usually at a lower level than normal kidneys. Its renal pelves are displaced anteriorly and its ureters usually course across the anterior surfaces of the kidney. Dysplastic development may occur in the fused portion of the kidney.
The ureters may be duplicated or angulated, so that obstruction, which leads to hydronephrosis, occurs.
Ectopic Kidney
A kidney is ectopic when it is in the pelvis and not in its usual location. Ureter duplication is a double ureter that can be unilateral or bilateral. Ectopic kidney and ureter duplication usually are not functionally important in the prenatal period. Their frequency is increased in chromosome aneuploidies.
Renal Agenesis
In bilateral renal agenesis, both kidneys and ureters are absent (Table 19.1).
Bilateral renal agenesis is rare, occurring in 1/3,000 to 1/4,000 live borns (Figure 19.4). Unilateral agenesis occurs in 1/1,000 newborns; it is more common in males.
It is postulated that renal agenesis is caused by the failure of the ureteric bud to develop. The ureteric bud normally induces the metanephric blastema to become a kidney.
16 - Cardiovascular System Defects
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
PRENATAL DIAGNOSIS
With the advent of ultrasound and its application to the human fetal heart,prenatal diagnosis and management of structural heart disease and cardiacdysrhythmia is possible (Figure 16.1). Congenital heart disease is relatively uncommonin the general population, and not every pregnancy can or should be examined with fetal echocardiography. Only those pregnancies with recognized risk factors for cardiac disease and those with an abnormal four-chamberview on level I obstetrical sonograms should be evaluated.
TECHNIQUE OF FETAL ECHOCARDIOGRAPHY
The fetal heart is most easily examined by ultrasound transabdominally at 18-24 weeks gestation, when a nonfixed fetal position, incompletely calcifiedbones, and abundant amniotic fluid make cardiac imaging easier (Table 16.1). Transvaginal images show excellent cardiac detail as early as 14 weeks gestation. Transvaginal imaging is invasive, however, and carries a small potential risk, it should be used when transabdominal imaging is inadequate. Transabdominal ultrasound uses a relatively high-frequency transducer to examine the heart and great vessels segmentally. It uses M-mode, two-dimensional, pulsewave, and color flow Doppler to delineate the cardiac anatomy, fetal hemodynamics, and patency of the fetal circulatory pathways. Anormal fetal echocardiogram does not eliminate the potential for congenital heart disease. Lesions that may not be identified prenatally include mild semilunar valve obstruction, atrial septal defect, small ventricular defect, and partial anomalous venous return. In addition, coarctation of the aorta is a significant lesion that is difficult to diagnose.
The early fetal heart can be dissected under a dissecting microscope in the same manner as the heart of anolder fetus or a newborn (illustrated in Chapter 3).
18 - Gastrointestinal Tract and Liver
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
ESOPHAGEAL ATRESIA (SEE ALSO CHAPTER 17)
Esophageal atresia results in a complete separation of the esophagus into upper and lower segments. This is often accompanied by communication of either segment or both with the trachea resulting in tracheoesophageal fistula (TEF). It is accompanied by polyhydramnios in which the fetus is unable to swallow amniotic fluid.
The incidence is from 1/800 to 1/5,000 live births.
Pathogenesis
At approximately 4 weeks of development, a diverticulum grows caudally from the ventral wall of the foregut to form the trachea and esophagus. Tracheoesophageal folds forma tracheoesophageal septum, which separates the trachea from the esophagus at the 5th week of embryonic development.
If there is failure of normal septum formation, it results in a TEF with two disconnected segments of the esophagus.
Esophageal atresia is usually sporadic, although there have been about 80 reports of familial atresia with TEF. It also may occur in trisomy 18 or 21.
In over 80% of cases, the upper esophageal segment ends blindly and the lower segment communicates with the trachea (TEF). In approximately 10%, there is isolated atresia of the esophagus; in 1-3%, the upper segment joins the trachea; in 5%, both segments join the trachea. In the region of the fistula, the trachea is often narrow, and tracheal cartilage may be hypoplastic or absent. (See Chapter 17.)
The most frequently associated malformations are gastrointestinal defects, with about one-half associated with an imperforate anus. Cardiovascular malformations, such as persistent ductus arteriosus, VSD, ASD, right-sided aortic arch, dextrocardia, and urogenital defects, such as renal agenesis and hydronephrosis may be associated.
Acknowledgments
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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20 - Congenital Tumors
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
Congenital tumors are often composed of persistent embryonal or fetal tissues, suggesting a failure of proper cytodifferentiation or maturation during early life. Neuroblastoma develops from neural crest cells that migrate into the gland during embryonic and fetal life. Normally, these cells mature to ganglion cells.
Morphologic features of embryonic neoplasms include retinoblastoma, peripheral primitive neuroectodermal tumor (PNET), hepatoblastoma, yolk sac tumor of the testis, and embryonal rhabdomyosarcoma. Some teratomas show proliferation ofembryonic tissues that fail tomature. Anumberof tumors in the young are associated with congenital malformations and growth disturbances.
Some embryonic tumors have a benign course despite a malignant microscopic appearance such as stage IV-S neuroblastoma, congenital fibrosarcoma, and nephroblastomatosis. These tumors may undergo cytodifferentiation and spontaneous regression. Malignant neoplasms are seldom seen in the newborn and only infrequently are responsible for neonatal death or spontaneous abortion. Chromosomal abnormalities associated with childhood tumors are shown in Table 20.1.
VASCULAR TUMORS
Hemangiomas are the most common tumors of the skin and soft tissues in infants (Figure 20.1).
Benign Hemangiomas
Capillary hemangioma usually manifests at birth, grows steadily for 68 months, then stabilizes, and eventually regresses, although complete disappearance may take several years. It is composed of capillaries separated by stroma. It may present as a raised subcutaneous nodule that blanches under pressure. Because childhood hemangiomas are tumors that evolve in time, a capillary hemangioma is thought to originate from a more primitive form.
15 - Skeletal Abnormalities
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
OSTEOCHONDRODYSPLASIAS
Bone is formed from collagen. Bone dysplasias predominantly involve one type of collagen (Figure 15.1). Terms used in the description of bone dysplasias according to the defect in collagen are shown in Table 15.1.
The normal growth plate or physis consists of four zones:
resting cartilage;
proliferative cartilage;
hypertrophic cartilage;
zone of provisional calcification.
The revised international classification of osteochondrodysplasias encompasses those disorders that are perinatally lethal and/or amenable to prenatal diagnosis (Table 15.2). Prenatal diagnosis has been made in most of the lethal forms of ostechondrodysplasia (Table 15.3). The osteochondrodysplasias include the infant or fetus with dwarfism. Most are lethal. For most convenience in diagnosis they can be divided into the following groups:
■ Osteochondrodysplasias with platyspondyly
■ Osteochondrodysplasias with short trunk
■ Short rib osteochondrodysplasias
■ Osteochondrodysplasias with defective bone density
■ Miscellaneous group
Osteochondrodysplasias with Platyspondyly (Table 15.4)
Although the trunk of the infants in this group is not significantly short, the vertebral bodies in the radiograph are markedly flattened. Histopathologically the physeal growth zones are usually disorganized and may be retarded, but the resting cartilage is mostly unremarkable.
24 - Metabolic Diseases
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Most metabolic disorders due to inborn errors of metabolism are inherited as autosomal recessive traits; some are X-linked. A few are dominant traits. Mitochondrial enzymes are coded by both the maternal nuclear genome and by the mitochondrial DNA. Some disorders can be detected by newborn screening (Table 24.1). Placental changes (Table 24.2) may be present and suggest a lysosomal storage disease. Skin fibroblasts, conjunctiva, intestinal biopsy, peripheral nerve, muscle, bone marrow and amniocytes may be used in the diagnoses of metabolic disease (Table 24.3). Vacuolated lymphocytes (Table 24.4) also may be seen in a number of storage diseases.
AMINO ACID DISORDERS
A number of disorders of amino acid metabolism have been described including phenylketonuria, tyrosinemia, alkaptonuria, homocystinuria, lysinemia, and cystinosis (Figures 24.1 and 24.2 and Tables 24.5 and 24.6). These disorders are rarely observed in the fetus or newborn infant.
MUCOPOLYSACCHARIDOSES
These disorders are distinguished by storage of glycosaminoglycans (GAG) (mucopolysaccharides) and glycolipids in the lysosomes of different cell types, including fibroblasts, macrophages, white blood cells, parenchymal cells of liver, kidneys, brain and other organs, and neurons, and by excretion of mucopolysaccharide in the urine (Table 24.7).
When the tissue is fixed in GAG-insoluble fixatives such as alcohol, the accumulated material shows intense metachromasia (purple-blue staining) with toluidine blue and stains with Alcian blue, weakly with periodic acid-Schiff (PAS), and is impregnated with colloidal iron. Lipid may be abundant.
Hurler disease is characterized by coarse features, prominent supraorbital ridges, depressed nasal bridge and dysostosis multiplex (Figures 24.3 to 24.5). Beaking of the vertebral bodies may be apparent in the fetus and newborn.
Frontmatter
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Appendices
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
APPENDIX 1. CYTOGENETIC TERMINOLOGY
Aneuploid. An unbalanced state that arises through loss or addition of whole or pieces of chromosomes; always considered deleterious.
Chromosome. The location of hereditary (genetic) material within the cell. This hereditary material is packaged in the formof a very long, double-stranded molecule of DNA surrounded by and complexed with several different forms of protein. Genes are found arranged in a linear sequence along chromosomes, as is also a large amount of DNA of unknown function.
Confined placental mosaicism. A viable mutation in trophoblast or extraembryonic progenitor cells of the inner cell mass resulting in dichotomy between the chromosomal constitution of the placenta and the embryo or fetus.
Deletion. Pieces of chromosomes are missing in persons having 46 chromosomes.
Diploid (2n). The whole set of 46 chromosomes in a somatic cell.
Duplications. Extra pieces of chromosomes occur in individuals with 46 chromosomes.
Endomitosis. Duplication of the chromosomeswithout accompanying spindle formation or cytokinesis, resulting in a polyploid nucleus.
4 - Ultrasound of Embryo and Fetus: General Principles
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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ABSTRACT
The area of obstetric ultrasonography has undergone rapid and dramatic evolution over the past three decades. Initial imaging studies were limited to rudimentary evaluations of fetal position and identification of amniotic fluid pockets to the current state of the art, which offers the potential for three-dimensional image reconstructions and targeted Doppler sonographic interrogation of the heart and cerebral vascular structures. Because of the rapid pace of change within the field, several professional organizations offer guidance about routine performance of obstetric ultrasound. In the United States, the American College of Obstetrics and Gynecology (ACOG), the American College of Radiology (ACR), and the American Institute of Ultrasound in Medicine (AIUM) have offered guidelines for obstetric sonography, while in the British Commonwealth, the Royal College of Obstetrics and Gynecology (RCOG) of England, and the Society of Obstetrics and Gynecology of Canada (SOGC) offer recommendations and guidance. Potential resources include the following publications: ACOG, Practice Bulletin 27; ACOG, Technical Bulletin 187, Ultrasonography In Pregnancy (12/93) (http://www.acog.org); ACR, Standard for the Performance of Antepartum Obstetrical Ultrasound (http://www.acr.org); AIUM, Standards for Performance of the Antepartum Obstetrical Ultrasound Examination (http://www.aium.org); RCOG, Ultrasound Screening for Fetal Anomalies and the Value of Ultrasound in Pregnancy (http://www.rcog.org.uk); SCOG, Guidelines of Ultrasound as Part of Routine Prenatal Care (8/99), Obstetrics/Gynecologic Ultrasound (7/97) (http://www.sogc.medical.org).
3 - Fetal Autopsy
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Summary
The normal anatomy of the adult and child are similar; however, the perinatal autopsy is significantly different. The variety and complexity of the congenital anomalies found in perinatal and fetal autopsies is endless and the prosector must be prepared to spend the necessary time demonstrating these anomalies. This detailed procedure can be altered to preserve any anomaly encountered without deforming the body itself. Most of the anomalies found in this population never survive to adulthood. Together with the clinical information this meticulous examination provides the necessary information to educate the families about future pregnancies.
PLACENTAL CHANGES AFTER FETAL DEATH
After the intrauterine death of the fetus, the placenta remains vital until it is expelled. However, changes occur that resemble vascular insufficiency but are diffuse, affecting fetal structure and all villi (Figure 3.1). Focal lesions suggest a preexisting abnormality (Tables 3.1).
Fetal death results in complete interruption of the fetal circulation. Vascular spaces within the villi are empty and collapsed. Within weeks, ingrowth of fibroblasts ultimately completely obliterate the vessels. Thrombosis does not occur and if present indicates preexistent pathology.
Calcificationmay be observed in addition to fibrosis as a postmortemchange within villi. It presents as fine granules deposited along the basal membrane of the trophoblast, sometimes almost in linear fashion. The fine granules contrast with the coarse deposits that sometimes occur in villi during physiological maturation. After fetal death, there are excessive syncytial knots that are diffuse. Primary vascular insufficiency is usually focal.
12 - Fetal Hydrops and Cystic Hygroma
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Summary
Minor hydrops is common, particularly in premature infants. Severe hydrops is generalized edema of 7.5 mm subcutaneous edema in a third-trimester fetus with an effusion of at least one body cavity, usually accompanied by polyhydramnios and edema of the placenta.
POLYHYDRAMNIOS
Amniotic fluid volume is approximately 800 mL at term. The volume is increased by fetal urine and is simultaneously removed by fetal swallowing. Fetal anomalies that interfere with swallowing are associated with polyhydramnios, while a decrease of fetal renal function and production of urine result in oligohydramnios. The volume of amniotic fluid falls rapidly after 40weeks gestation to about 400 mL at 42 weeks and 200 mL at 44 weeks. Polyhydramnios is the presence of an excess of 1,500 mL of amniotic fluid at term and is present in up to 1% of pregnancies.
Causes of polyhydramnios
I. Maternal
A. Diabetes and gestational diabetes
II. Fetal anomalies
A. Anencephaly
B. Esophageal atresia
C. Small intestinal obstruction
D. Diaphragmatic hernia
E. Central nervous system malformations
F. Chromosomal defects
III. Placenta
A. Chorangioma
FETAL HYDROPS (FH)
Hydrops fetalis (HF) has a mortality rate in excess of 90% (Tables 12.1 to 12.5).
Intrauterine diagnosis of hydrops by ultrasound may allow successful treatment and reversal in selected cases, but the majority die without an established causative diagnosis.
13 - Central Nervous System Defects
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Summary
Central nervous system (CNS) defects are the most common developmental defects both at birth and in spontaneously aborted conceptuses. The incidence is from 1 to 65 per 1,000 births.
The incidence of neural tube defects in embryos fromspontaneous abortions is about 10 times higher than in newborns. In aborted embryos, CNS defects are usually components of chromosomal syndromes that are lethal early in development and thus are seen less commonlyin aborted fetuses that have fewer chromosome anomalies. Most fetal specimens with CNS defects, therefore, are obtained from terminated pregnancies after prenatal detection of an isolated CNS defect.
NEURAL TUBE FORMATION
Neurulation occurs between days 20 and 30 of embryonic development (Stages 9-12) (Figures 13.1 to 13.3 and Table 13.1). Failure of the neural folds to fuse during this period results in a permanent open neural tube defect. Five sites of closure have been proposed. However, careful study of a series of staged human embryos has shown only two de novo sites of fusion: in the rhomboencephalon that proceeds rostrally and caudally, and in the prosencephalon that fuses caudally. It is debated whether failure of closure is due to a deficiency in the axial cephalic mesoderm or in the neuroepithelium itself, but in either case the result is an eversion of the cephalic neural tube and absence of the cranium in anencephaly.
The first sign of neurulation is the appearance of the neural plate in Stage 8. The neural folding process begins at Stage 9.
11 - Intrauterine Growth Retardation
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Summary
Estimation of fetal maturity is the most accurate method of estimating gestation age by ultrasonographic measurements of crown-rump length during the first trimester. From the first trimester through 34 weeks, the biparietal diameter is accurate to within 10 days. Other measurements used in the 2nd and 3rd trimesters include fetal abdominal diameter and femur length.
Low birth weight (LBW) is a worldwide problem usually defined as birth weight <2,500 g, irrespective of gestational age. It is associated with increased perinatal morbidity and is used as a marker of increased neonatal risk. It is not an ideal marker of fetal growth and development and combines both prematurity and various degrees of growth retardation.Morbitity is associated with LBW and growth retardation. Twenty-one million LBW infants are born each year internationally, 90% in developing countries.
Insulin growth factor (IGF) II is essential for organogenesis and early fetal growth. IGF-I is essential for late fetal growth. IGF-I is low in intrauterine growth retardation (IUGR) infants.
Proportion of LBWs varies by type of society:
■ 3–12% rates of LBW infants occur in developed countries, 60% premature, 40% growth retarded
■ 12–40% rates of LBW in developing countries, 20% premature, 80% growth retarded
There is a high rate of perinatal morbidity in growth-retarded infants:
■ perinatal depression is 3 times more likely
■ hypoglycemia is 4–6 times more likely
■ hypothermia is 5 times more likely
■ meconium aspiration is 13 times more likely
■ fetal distress in labor is 6 times more likely
Contents
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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Embryo and Fetal Pathology
- Color Atlas with Ultrasound Correlation
- Enid Gilbert-Barness, Diane Debich-Spicer
- Foreword by John M. Opitz
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Exhaustively illustrated in color with over 1000 photographs, figures, histopathology slides, and sonographs, this uniquely authoritative atlas provides the clinician with a visual guide to diagnosing congenital anomalies, both common and rare, in every organ system in the human fetus. It covers the full range of embryo and fetal pathology, from point of death, autopsy and ultrasound, through specific syndromes, intrauterine problems, organ and system defects to multiple births and conjoined twins. Gross pathologic findings are correlated with sonographic features in order that the reader may confirm visually the diagnosis of congenital abnormalities for all organ systems. Obstetricians, perinatologists, neonatologists, geneticists, anatomic pathologists, and all practitioners of maternal-fetal medicine will find this atlas an invaluable resource.
21 - Fetal and Neonatal Skin Disorders
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
SEBORRHEA AND DRY DESQUAMATION
Miliaria
Secretion of sweat normally exudes from the glands but occasionally collects in the gland ducts, distending them so that they are visible at birth as discrete pinpoint elevations known as milia crystalline (Figure 21.1). They usually disappears during the first week of life. They are most often visible on the forehead, cheeks, and sides of the nose. Microscopically a keratinous plug and an intra- or subcorneal vesicle communicates with the underlying sweat duct, sometimes with a mild inflammatory infiltrate. When the process is deeper, prickly heat (miliaria rubra) occurs.
Milia are pearly yellow 1 to 3-mm papules on the face, chin, and forehead of 50% of newborns. Occasionally they erupt on the trunk and extremities. Although milia usually resolve without treatment during the first month of life, they may persist for several months. Microscopically they are miniature epidermal inclusion cysts, which arise from the pilosebaceous apparatus of vellus hairs.
Seborrheic Dermatitis
The scalp is most often affected in the newborn and is often associated with incomplete removal of the vernix caseosa. The lesions are poorly defined, yellowred salmon-colored patches covered by waxy, greasy, easily removed scales.
Acanthosis, edema, and occasional perivascular infiltration of leukocytes are present as well as spongiosis of the basal layer seen microscopically (Figure 21.2).
Index
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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- Embryo and Fetal Pathology
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10 - Disruptions and Amnion Rupture Sequence
- Enid Gilbert-Barness, University of South Florida and University of Wisconsin Medical School, Diane Debich-Spicer, University of South Florida
- Foreword by John M. Opitz, University of Utah
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Summary
Disruption is defined as a morphologic or structural anomaly of an organ, part of an organ, or a larger region of the body resulting from the extrinsic breakdown of, or interference with, an originally normal conceptus or developmental process. Disruptions tend to be sporadic occurrences (Figure 10.1 and Tables 10.1 to 10.6).
TYPES OF DISRUPTIONS AFFECTING MORPHOGENESIS OF THE DEVELOPING EMBRYO AND FETUS
■ Radiation
■ Hyperthermia
■ Infection
■ Teratogenic drugs
■ Metabolic
■ Vascular
■ Amnion disruption
TERATOGENIC DISRUPTIONS
Growth and development of the embryo can be adversely affected by a wide variety of environmental agents (teratogens). Teratogens include intrauterine infections, various chemical agents and medications, and maternal metabolic disorders.
The first two weeks of life that is, the time before organogenesis appears to be a relatively safe time for the embryo regarding teratogenic exposure. The next 45 days, however, are especially dangerous for it is during this period that most organs develop. After an organ has developed, unless there is disruption, the teratogen cannot cause a malformation. The same teratogen can cause different defects at different times of exposure.
Most teratogens produce a characteristic, clinically recognizable, pattern of abnormalities.
RADIATION EMBRYOPATHY
In utero radiation is associated with microcephaly, mental retardation, and stunted growth, especially in infants exposed between the 8th and 15th weeks of gestation, and there is an increased incidence of leukemia.
HYPERTHERMIC EMBRYOPATHY
Hyperthermia, a body temperature of at least 38.9°C, is an antimitotic teratogen when the fetus is exposed to a high temperature between the 4th and 16th week of gestation (Figure 10.2 and Table 10.7).