Pediatrics

Congenital anomalies

morphologic defect present at birth, may not become clinically significant later, most common cause of mortality in first year

malformation

intrinsic error in development (morphogenesis), multifactorial; ex: microcephaly, congenital heart disease

disruption

secondary destruction, extrinsic disturbances in morphogenesis; ex: amniotic bands → shortened arm

deformation

mechanical compression; ex: uterine constrain → club foot

sequence

single initiating event → cascade; ex: oligohydramnios → potter sequence (flattened head and deformed feet)

syndrome

multiple related anomalies; ex: TORCH complex

agenesis

complete absence of organ and primordium

aplasia

absence of organ due to primordium development failure

hypoplasia

incomplete development

hyperplasia

enlargement of an organ due to increased number of cells

hypertrophy

enlargement of an organ due to increase in size of cells

hypotrophy

decrease in size of organ due to a decrease in size of cells

dysplasia

abnormal organization of cells

causes of anomalies

75% unknown, genetic (chromosomal, single-gene, multifactorial), environmental (TORCH infections, drugs/chemicals, radiation, maternal diabetes)

TORCH complex

toxoplasmosis, others, rubella, CMV, herpes, simplex

others = syphilis, hepatitis, HIV, parvovirus, varicella, zika

teratogen

substance that causes birth defects/developmental abnormalities in a fetus; timing is critical → determines type of severity

Most critical time span for teratogen exposure

weeks 3-9 (embryonic period) extremely susceptible to morphologic abnormalities; weeks 4-5 = organogenesis

Prematurity

before 37 weeks, 2ns most common cause of neonatal mortality
causes: PPROM (preterm premature rupture of membrane), intrauterine infection, uterine/cervical abnormalities, multiple gestation

Neonatal Respiratory Distress Syndrome (RDS)

cause: surfactant deficiency (type II)
risk: prematurity, maternal diabetes

pathology: atelectasis, hyaline membranes, hypoxemia

tx: corticosteroids (antenatal), exogenous surfactant prevention

pathogenesis of neonatal respiratory distress syndrome

prematurity → reduced synthesis of surfactant → deficiency of alveolar surfactant →increased alveolar surface tension → collapse of lung → pulmonary hypoperfusion → damage to endothelium/epithelium → plasma leaks into alveoli → deposition of fibrin and necrotic cells (hyaline)

hemolytic disease of the fetus and newborn (HDFN)

Rh incompatibility between mother and fetus, mother is Rh- and fetus is Rh+; first pregnancy: IgM without crossing placenta, second pregnancy: IgG cross placenta → fetal hemolysis, hydrops fetalis, kernicterus
prevention: anti-D immunoglobin (Rhogam)

hydrops fetalis

accumulation of edmatous fluid, caused by immune hydrops (Rh incompatibility - HDFN)

congenital rubella syndrome

teratogen, risk period: first 8 weeks > second 8 weeks; causes cataracts, heart defects, deafness, learning disabilities

fetal alcohol spectrum disorders

teratogen; causes intrauterine growth restriction, microcephaly, atrial septal defect, short palpebral fissures, maxillary hypoplasia, cognitive and behavioral issues

heterotopia

normal cells or tissue in an abnormal location; benign tumor

hamartoma

local, excessive growth of cells/tissue native to the organ (overgrowth); benign histology but can be life threatening

hemangioma

tumor made up of blood vessels, most common benign tumor, port-wine stains, regress spontaneously

lymphangioma

malformations of lymphatic system, cystic/cavernous spaces, increase in size, secondary to chromosomal abnormality; benign tumor

lymphangiectasis

abnormal dilation of preexisting lymph channels causing distortion of an extremity; benign tumor

fibrous tumor

spindle shaped cells, associated with chromosomal translocations, benign tumor

teratoma

mature vs immature, malignant potential, most common = sacrococcygeal teratoma

mature teratoma

cystic lesions made up of muscle, bone, hair, and/or teeth

common malignant pediatric tumors

1. hematopoietic (leukemia) 2. nervous tissue 3. soft tissue 4. bone 5. kidney

common malignant tumors in adults

1. breast 2. prostate 3. lung 4. colon

pediatric vs adult malignancy

incidence and type, role of teratogenesis and oncogenesis, familial or genetic, regression/cytodifferentiation, better cure rates in peds

most common malignancy in children

leukemia

neuroblastic tumors

tumors of sympathetic ganglia/adrenal medulla, most common extra-cranial solid tumor
gross: adrenal mass, along sympathetic chain
micro: schwann cells (favorable prognosis), rosettes “homer-wright pseudorosettes”, neuropil, small round blue cells, dark nuclei, scant cytoplasm, poor defined
clinical features: <2 years, abdominal mass, fullness/pain, HTN, fever, weightloss, catecholamine secretion

Wilms tumor

most common pediatric renal tumor, peak age 2-5, high risk of secondary malignancies, 85% cured
gross: large, well-circumscribed, hemorrhagic foci, necrosis
micro: triphasic combination, anaplasia

clinical features: abdominal mass without other symptoms, hematuria, HTN, fever, lung = most common metastasis

triphasic combination

blasternal (small blue cells), stromal (fibrocytic/myxoid), epithelial (tubules or glomeruli)

pathogenesis of wilms tumor

abnormal proliferation of immature, undifferentiated kidney cells (nephroblast) that fail to mature during fetal development, leading to tumor formation after birth