Chapter 10: Diseases of Infancy and Childhood Flashcards
Primary errors of morphogenesis, in which there is an intrinsically abnormal developmental process defines?
Malformations
Secondary destruction of an organ or body region that was previously normal in development; thus arising from extrinsic disturbancs in morphogenesis defines what?
Classic example?
- Disruptions
- Amniotic bands, denoting rupture of amnion w/ resultant formation of “bands” that encircle, compress, or attach to parts of developing fetus
What is the most common underlying factor for the development of deformations in newborns?
Example of common deformation seen in Potter sequence?
- Uterine constraint: size of fetus outpaces the growth of uterus (35th-38th week)
- Deformations are caused by abnormal biomechanical forces
- Club feet is deformation seen in Potter sequence
What is the classic example of a sequence?
Due to what and what abnormalities are produced?
- Oligohydramnios (Potter) sequence
- Decreased amniotic fluid –> flattened facies and positional abnormalities of hands and feet; dislocated hips; hypoplastic lungs
- Nodules (amnion nodosum) in the amnion of frequently present
Malformations, disruptions, or deformations that set into motion secondary effects in other organs is known as?
A sequence = cascade of anomalies triggered by one initiating aberration
A constellation of congenital anomalies, believe to be pathologically related, but cannot be explained on the basis of a single, localized, initiating defect defines what?
Malformation syndrome
What is frequently present in Oligohydramnios (or Potter) sequence?
Nodules in the amnion (amnion nodosum)
Differentiate agenesis from aplasia
Agenesis: complete absence of an organ AND its associated primordium (absent primordium)
Aplasia: absence of an organ but one that occurs due to failure of growth of the existing primordium (primordium exists)
What are the most common microbes to cause congenital abnormalities during development? (hint: mnemonic = TORCH)
T - Toxoplasmosis
O - Other - Syphillis
R - Rubella
C - CMV
H - Herpes/HIV
Maternal hyperglycemia-induced fetal hyperinsulinemia results in what disorders in the fetus? (Diabetic embryopathy)
- Macrosomia (organomegaly and increased body fat and muscle mass)
- Cardiac anomalies
- Neural tube defects
- CNS malformations
*The major defects in diabetic embryopathy
What 7 drugs/chemicals have been known to cause congenital anomalies in humans?
1) Alcohol
2) Folic acid antagonists
3) Androgens
4) Phenytoin
5) Thalidomide
6) Warfarin
7) 13-cis-retinoic acid
What is the most common genetic cause of congenital malformations?
What common malformations are included in this category?
- Multifactorial inheritance
- Cleft lip, cleft palate, and neural tube defects
Major morphological abnormalities occur during which weeks of embryonic development?
Weeks 3-7
Between which weeks is the embryo extremely susceptible to teratogenesis?
Peak sensitivity when?
- Extremely sensitive = Weeks 3-9
- Peak sensitivity = 4-5th week
Teratogens during the 4th and 5th weeks of gestation affect every body system except for?
Teeth, palate, and genitalia
The antiepileptic drugs, Valprotic acid, disrupts expression of what developmentally critical TF?
Causes what?
- Disrupts HOX proteins that help limb pattern development, vertebrae, and craniofacial structures
- Mutations in the HOX family of genes are responsible for congenital anomalies that mimic features observed in valproic acid embryopathy
Thalidomide, once used as a tranquilizer in Europe, causes an extremely high incidence of?
Limb malformations
Infants born to mothers treated with retinoic acid for severe acne have which predictable phenotype (retinoic acid embryopathy)?
CNS, cardiac, and craniofacial defects (cleft lip and cleft palate)
The craniofacial defects (cleft lip and palate) which result from retinoid acid embryopathy are a result of?
Retinoic acid-mediated deregulation of the TGF-B signaling pathway
What defines prematurity?
Second most common cause of?
- Gestational age less than 37 weeks
- Second most common cause of neonatal mortality
What are the 4 risk factors associated with prematurity?
1) PPROM (before 37 weeks = most serious)
2) Intrauterine infections (major cause)
3) Structural abnormalities (uterine, placental, and cervical)
4) Multiple gestations (twin pregnancy)
What are the most common microorganisms implicated in intrauterine infections leading to preterm labor?
- Ureaplasma urealyticum
- Mycoplasma hominis
- Gardnerella vaginalis
- Trichomonas
- Gonorrhea
- Chlamydia
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What is the molecular mechanism by which intrauterine infections induce preterm labor?
- Endogenous TLRs bind bacterial compounds
- Produce signals which deregulate prostaglandin expression, in turn producing smooth muscle contractions
Which fetal conditions cause Fetal Growth Restriction (FGR)?
Infections by what agents?
- Chromosomal disorders,
- Congenital anomalies
- Congenital infections (TORCH = most commonly responsible)
Infants who are SGA because of fetal factors usually have which type of growth restriction?
Also referred to as?
Symmetric growth restriction (also referred to as proportionate FGR) = all organ systems are similarly affected
Placental causes of FGR tend to result in what type of growth retardation of the fetus?
Asymmetric (or disproportionate) growth retardation w/ relative sparing of the brain
What are the most common maternal abnormalities/conditions associated with SGA infants?
- Vascular diseases = Preeclampsia (toxemia of pregnancy) and Chronic HTN
- Thrombopilias (i.e., acquired antiphospholipid antibody syndrome)
- Narcotic abuse, alcohol intake, and heavy cig smoking
- Maternal malnutrition (i.e., prolonged hypoglycemia)
What is found deposited in the peripheral airspaces of infants who succumb to Respiratory Distress Syndrome (RDS)?
Hyaline proteinaceous material
What are the strong associations with RDS?
- Male gender
- Maternal diabetes
- C-section
What are the major morphological features of RDS?
Cyanosis
Fine rales over both lung fields
Ground-glass on X-ray
Which surfactant-associated proteins play a role in pulmonary host defense?
Which are involved in reduction of surface tension at the air-liquid barrier?
- SP-A and SP-D are involved in host defense (innate immunity)
- SP-B and SP-C + Surfactant lipids are involved in reducing surface tension
What hormones and GFs are responsible for modulating the synthesis of Surfactant?
Which is particularly important?
- Prolactin
- Insulin (suppresses synthesis)
- Cortisol (particularly important)
- Thyroxine
- TGF-B
*Role of glucocorticoids are particularly important
Conditions associated with intrautrerine stress and FGR that increase corticosteroid release have what effect on infants developing RDS?
Can be counteracted by?
- Lowers the risk of developing RDS
- Compensatory high levels of insulin in infants of diabetic mothers, counteracts the effects of steroid and suppresses surfactant synthesis
What are the 2 complications of prolonged therapy with high concentration of ventilator-administered oxygen for RDS?
1) Retrolental fibroplasia
- Phase I: VEGF is decreased = endothelial apoptosis
- Phase II: VEGF levels rebound upon return to hypoxic room air ventilation, inducing retinal vessel proliferation
2) Bronchopulmonary dysplasia –> increased levels of pro-inflammatory cytokines –> decreased alveolar septation
What are the morphological characteristics of RDS?
- Lungs normal size, solid, airless, and reddish-purple in color
- Alveoli poorly developed and collapsed – atelectasis
- Necrotic cells (type II pneumocytes) seen early and later incorporated within eosinophilic hyaline membranes also composed of fibrin
Bronchopulmonary dysplasia as a result of high concentrations of ventilator-administered oxygen is caused by potentially reversible impairment in the development of alveolar septation at what stage?
Saccular stage
Infants who recover from RDS are also at increased risk for developing what other complications associated with pre-term birth?
- Patent ductus arteriosus
- Intraventricular hemorrhage
- Necrotizing enterocolitis
Most cases of Necrotizing Enterocolitis are associated with?
Enteral feeding
Which inflammatory mediator is commonly seen in Necrotizing Enterocolitis?
Function?
- PAF
- Increasing mucosal permeability by:
- Promoting enterocyte apoptosis and
- Compromising intercellular tight junctions
Abdominal radiographs in infants with Necrotizing Enterocolitis often show?
Pneumatosis intestinalis (gas within intestinal wall)
Necrotizing enterocolitis typically involves which structures?
Terminal ileum
Cecum
Right colon
What are the 2 primary routes in which fetal and perinatal infections are acquired?
1) Transcervically (also called ascending)
2) Transplacentally (hematologic)
Most bacterial and few viral (herpes simplex II) are acquired via which route?
Cervicovaginal route
Most parasitic (toxoplasma, malaria), viral, and few bacterial infections (Listeria, Treponema) gain access to the fetal bloodstream how?
Transplacental (Hematologic) via Chorionic Villi
Parvovirus B19 has a particular tropism for which cells?
Seen how diagnostically?
- Erythroid cells
- Diagnostic viral inclusions can be seen in early erythroid progenitors
TORCH group of infections evoke similar clinical and pathologic manifestations including?
- Fever
- Encephalitis
- Chorioretinitis
- Hepatosplenomegaly
- Pneumonitis
- Myocarditis
- Hemolytic anemia
- Vesicular or hemorrhagic skin lesions
Most common cause of early-onset sepsis as well as early-onset meningitis?
Group B streptococcus
What are the major antigens known to induce clinically significant immunologic reactions leading to Immune Hydrops?
Certain of the Rh antigens and the ABO blood groups
Of the numerous antigens included in the Rh system, which antigen is the major cause of Rh incompatibility?
D antigen
The incidence of maternal Rh isoimmunization has decreased significantly since the use of?
When is it administered?
- Rhesus immune globulin (RhIg) containing anti-D antibodies
- Administered at 28 weeks and within 72 hours of delivery to Rh-negative mothers
ABO hemolytic disease occurs almost exclusively in which infants and mothers?
Occurs during what pregnancy?
- Infants of group A or B who are born to group O mothers
- Can occurs during the first pregnancy, unlike in Rh-mediated immune hydrops
What are the 3 major causes of nonimmune hydrops?
1) Cardiovascular defects
2) Chromosomal anomalies (Turner syndrome - cystic hygromas + trisomies 21/18 - CV problems)
3) Fetal anemia
In some parts of the world (i.e., Southeast Asia), what is the most common cause of severe fetal anemia —> nonimmune hydrops?
Homozyogous α-thalassemia, resulting from deletion of all four α-globin genes
Transplacental infection by which virus is rapidly emerging as an important cause of hydrops?
Parvovirus B19
In hydrops associated with fetal anemia, both the fetus and placenta are characteristically pale; what organ morphologies are seen?
Major morphologic feature of the liver?
- Liver and spleen are enlarged from cardiac failure and congestion
- Extramedullary hematopoiesis present in liver, spleen, and LNs
Increased numbers of RBCs, including reticulocytes, normoblasts, and erythroblasts seen in hydrops due to fetal anemia culminates to what?
Erythroblastosis fetalis
What is the most serious threat in fetal hydrops?
Morphological features?
- CNS damage, known as kernicterus (toxicity of bilirubin)
- Brain is enlarged and edematous, and when sectioned has a bright yellow , particularly the basal ganglia, thalamus, cerebellum, cerebral gray matter, and SC
Classic Phenylketonuria is distinctively common in which populations?
Uncommon in?
Inheritance pattern?
- Common in Scandinavian descent
- Uncommon in African American and Jews
- Autosomal Recessive
PKU is caused by a severe deficiency of what enzyme?
Converts phenylalanine to?
- Phenylalanine hydroxylase (PAH) = AR
- Needed for conversion of Phenylalanine —> Tyrosine
What is clinical findings and timeline seen in patients suffering from PKU?
- Normal at birth but develop rising plasma phenylalanine level, impairing brain development
- Present w/ Musty or Mousy odor to urine
- Usually by 6 months, there is severe mental retardation
If PKU is left untreated, what is seen in 1/3 and 2/3 of these patients?
What other major clinical consequences/findings?
- 1/3 of these children never able to walk
- 2/3 cannot talk
- Seizures, decreased pigmentation of hair/skin, and eczema
Explain how female PKU patients are able to reach adulthood and what occurs when they decide to have a child.
What is maternal PKU?
- Female PKU pts, if tx w/ dietary restriction early in life, reach childbearing age and are clinically asymptomatic; most have hyperphenylalaninemia due to dietary tx being discontinued after reaching adulthood
- Maternal PKU results from the teratogenic effects of phenylalanine or its metabolites that cross the placenta and affect specific fetal organs during development
How can the teratogenic effects of phenylalanine be avoided in children being born to mothers with PKU?
Imperative that maternal dietary restriction of phenylalanine be initiated BEFORE conception and continued throughout pregnancy
An infant presents with strong musty/mousy odor to the urine, what do you suspect?
PKU
What is responsible for the decreased pigmentation of the skin and hair seen in patients with PKU?
- Phenylalanine is not converted to tyrosine
- Tyrosine is a precursor of melanin
Clinically why is it important to recognize benign hyperphenylalaninemia?
How is it determined if you are dealing with benign vs classic PKU?
- These individuals may hav a positive screening test but do not develop the severe symptoms seen in classical PKU
- Measurement of serum phenylalanine is necessary to differentiate; classic PKU will have levels five-fold or more above normal
While 98% of PKU is attributable to mutation in PAH, how can the other 2% be accounted for?
Why is this clinically important?
- Abnormalities in the synthesis or recycling of the cofactor tetrahydrobiopterin (BH4)
- Clinically important to recognize these variant forms because they cannot be treated by dietary restriction of phenylalanine