Pediatric Diseases

Childhood: birth to 15 years - pediatric diseases: either unique to children or taking distinctive forms in children - diseases of infancy (first year of life): highest risk of mortality - neonatal period (first 4 weeks of life): most hazardous time

Congenital anomalies - structural defects present at birth - important cause of infant mortality Malformations - primary error of morphogenesis (abnormal development) - usually multifactorial - single or multiple organs may be involved Disruptions - secondary destruction of normally developed organ - not heritable (no risk of recurrence in subsequent pregnancies) amputation of limbs by amniotic bands Deformations - compression of growing fetus (uterine constraint) - malformed uterus, leiomyoma, multiple fetuses Agenesis - complete absence of the organ Hypoplasia - incomplete development or underdevelopment of the organ Atresia - absence of opening of the hollow organ (intestine, bile ducts)

Etiology of congenital anomalies Genetic causes - chromosomal abnormalities, gene mutations Environmental influences Infections - rubella (rubella embryopathy - eliminated by vaccination), toxoplasmosis, syphilis, CMV Maternal diseases - diabetes mellitus: diabetic embryopathy (macrosomia, cardiac anomalies, neural tube defects) - drugs: thalidomide (limb malformations - phocomelia), warfarin - alcohol: fetal alcohol syndrome: growth retardation, facial anomalies (microcephaly, maxillary hypoplasia) - cigarette smoking: spontanneous abortion, placental anomalies, low birth weight, SIDS - irradiation

Perinatal infections Transplacental - mostly viral and parasitic, a few bacterial infections - most important infections: TORCH (Toxoplasma, Other, Rubella, CMV, Herpes) - toxoplasma: hydrocephalus, brain calcifications, chorioretinitis - rubella: cataract (blindness), deafness, heart anomalies Transcervical (ascending) - during pregnancy (infected amniotic fluid) or delivery - Streptococci, Neisseria gonorrhoeae, herpes virus - usually associated with inflammation of placental membranes (chorioamnionitis) and umbilical cord (funisitis)

Prematurity - gestational age less than 37 weeks - second most common cause of neonatal mortality - higher incidence of morbidity Risk factors: - premature rupture of membranes - intrauterine infections (chorioamnionitis) - anomalies of placenta, uterus and cervix - twin pregnancy Complications: - respiratory distress syndrome - necrotising enterocolitis - CNS bleeding

Fetal growth restriction - one third of infants born in term but undergrown (weight less than 2.500 g): „small-for-gestational-age“ (SGA) - not only increased morbidity and mortality in perinatal period, but also problems in adult life (cerebral dysfunction, learning disability) Causes: Fetal - chromosomal disorders, congenital anomalies, congenital infections (TORCH group) - symmetric growth restriction (all organ systems affected equally) Placental - impaired uteroplacental supply - placenta previa, placental abruption, placental infarction - asymmetric growth restriction (brain spared relative to visceral organs) Maternal - preeclampsia, chronic hypertension, alcohol, drugs, smoking, malnutrition Unknown

Respiratory distress syndrome (RDS) Risk factors - prematurity (60% before 28th week, only 5% after 37th week) - maternal diabetes, cesarean section, twins Pathogenesis immature lungs cannot synthesize surfactant (complex of phospholipids reducing surface tension within alveoli) → alveoli tend to collapse → greater inspiratory effort → atelectasis (loss of lung volume) → hypoxia → epithelial and endothelial damage → hyaline membranes Morphology - airless, heavy lungs, mottled color congestion, solid appearance with collapsed alveoli hyaline membranes (necrotic cellular debris, extravasated fibrin) Complications (administration of high concentration of oxygen) Bronchopulmonary dysplasia - arrested development of alveolar septation → reduced number of mature alveoli and interstitial fibrosis → honeycomb lung Retrolental fibroplasia - retinal vessels proliferation → blindness

Necrotizing enterocolitis (NEC) - premature infants - intestinal ischemia (hypoperfusion) - bacterial colonisation of the gut - administration of formula feeds Macro: - terminal ileum, cecum, right colon most commonly involved - distended, friable, congested or gangrenous gut segment - intestinal perforation → peritonitis Micro: - mucosal or transmural necrosis - ulceration - submucosal gas bubbles - reparative changes: granulation tissue, fibrosis → post-NEC strictures

Perinatal brain injury - premature infants Intraparenchymal hemorrhage - within germinal matrix - subependymal location - primitive neural cells and thin-walled vessels - persists until 35th week - hypoxia → endothelial damage → hemorrhage - ventricular system (hematocephalus) - death, survivors: scarring → obstructive hydrocephalus Infarcts - supratentorial periventricular white matter - residual changes: chalky white plaques (mineralisation), large cystic lesions (multicystic encephalopathy)

Sudden Infant Death Syndrome “sudden death of an infant under 1 year of age which remains unexplained even after complete autopsy, examination of the death scene and revision of clinical history“ - infant usually dies while asleep („crib death“) - leading cause of death in infancy (USA: 3,000 cases annually) - in 90% of cases infants younger than 6 months unknown cause; hypothesis: delayed development of some regions of brainstem (arcuate nucleus) → impaired arousal response to noxious stimuli Risk factors: Maternal - young age, smoking during pregnancy, drug abuse (either parent), short intergestational intervals, low prenatal care, low socioeconomic status Infant - brain stem abnormalities (defective arousal and cardiorespiratory control), prematurity, male sex, multiple birth, SIDS in earlier sibling, respiratory infections Environment - prone sleep position, sleeping on soft surface, hyperthermia, passive smoking

Autopsy findings - multiple petechiae on thymus, pleura and epicardium lung congestion, lung edema - brain stem abnormalities (hypoplasia of arcuate nucleus, decrease of neuronal population) SIDS is diagnosis of exclusion; to be excluded: - infections (viral myocarditis, bronchopneumonia) - congenital anomalies - fatty acid oxidative disorders (medium chain acyl-coenzyme A dehydrogenase deficiency) - arrythmia (prolonged QT interval) - traumatic child abuse („shaken baby syndrome“)

Fetal hydrops - generalized edema of fetus (hydrops fetalis) or localized forms (pleural or peritoneal effusion) Causes: - fetal anemia - immune hydrops (Rh and AB0 incompatibility) - non-immune hydrops (α-thalassemia, parvovirus B19) - chromosomal abnormalities (trisomies, Turner syndrome) - cardiovascular abnormalities (heart defects) - infections (CMV, syphilis, toxoplasmosis) - „twin-twin transfusion“ syndrome

Immune hydrops - hemolysis of fetal RBCs induced by maternal antibodies - Rh or AB0 blood group incompatibility between mother and fetus - fetus inherits blood group antigens from father, that are foreign to mother (mother Rh-negative - fetus Rh-positive; mother 0 - fetus A or B) fetal RBCs reach maternal circulation (during last trimester of pregnancy or during delivery) → mother senzitized and develops antibodies next pregnancy: antibodies traverse placenta → destruction of fetal RBCs → fetal anemia → tissue ischemia → cardiac failure → edema Morphology - pale fetus and placenta - hepatosplenomegaly (congestion from cardiac failure) - hyperplasia of erythroid precursors within bone marrow extramedullary hematopoiesis (liver, spleen, kidney, lungs) - presence of immature red cells in peripheral blood (erythroblastosis fetalis) - hemolysis → unconjugated hyperbilirubinemia → toxic damage of brain (basal ganglia and brain stem) →yellow hue due to deposition of bilirubin pigment („kernicterus“)

Tumors of Infancy and Childhood Tumor-like lesions Hamartoma = focal overgrowth of tissue in organ where it normally occurs - linkage between malformations and true tumors (dividing line often not clear and variously interpreted) - hemangioma, lymphangioma, heart rhabdomyoma Choristoma = presence of normal cells in abnormal location - little clinical significance, may be confused with true tumors - pancreatic tissue in stomach wall, adrenal cortex in kidney, lung, ovary

Benign tumors Hemangioma (cavernous or capillary) - skin (face, scalp) - flat to elevated red blue mass („port wine stain“) - enlargement or spontaneous regression - rarely component of hereditary disorders (von Hippel-Lindau sy, Sturge-Weber sy) Lymphangioma - cystic and cavernous lymphatic spaces - skin or deep tissues (neck, axilla, mediastinum, retroperitoneum) - tend to enlarge after birth → compression of adjacent structures - component of Turner sy

Sacrococcygeal teratoma - most common germ cell tumor in childhood - 10% of cases associated with congenital anomalies of cloacal region and neural tube defects (spina bifida, meningocele) - majority of cases mature (benign) - rarely immature (malignant)

Malignant tumors - hematopoietic system, CNS and soft tissues most commonly involved - primitive („embryonal“) microscopic appearance: „small round blue cell tumors“ - tendency to differentiate into more mature elements - improved survival due to chemotherapy and radiotherapy → effort paid to minimizing of delayed adverse effects of treatment (secondary neoplasms)

Neuroblastoma - derived from primordial neural crest cells populating adrenal medulla and sympathetic ganglia - second most common solid malignancy in childhood (7-10% of all pediatric neoplasms; 50% of all pediatric malignancies) - most sporadic, a few autosomal dominant transmission (often multiple) from minute nodules to large masses Macro - soft, gray-tan tissue, areas of necrosis, cystic change and hemorrhage Micro - solid sheets of small primitive cells (neuroblasts) with dark nuclei and scant cytoplasm - faintly eosinophilic fibrillary background (processes of neuroblasts) - Homer-Wright rosettes - signs of maturation (spontaneous or therapy-induced): - ganglion cells admixed with neuroblasts (ganglioneuroblastoma) - ganglion cells and Schwann cell stroma (ganglioneuroma) - metastatic spread to liver, lungs and bones - production of catecholamines → metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA) within urine (screening markers)

Retinoblastoma - most common malignant eye tumor in childhood - may be congenital - sometimes spontaneous regression - high incidence of second primary tumors (osteosarcoma, soft tissue tumors) - sporadic (always unifocal and unilateral) or familial (often multiple and bilateral) from neuroepithelial cells of posterior retina Macro - nodular mass with satellite seedings Micro - small rounded cells with large dark nuclei - Flexner-Wintersteiner rossetes - metastatic spread to CNS, bones and lymph nodes - poor vision, strabismus, whitish hue to pupil (“cat’s eye reflex”) - untreated fatal, early treatment (enucleation, chemotherapy, radiotherapy) → survival

Nephroblastoma (Wilms’ tumor) - most common primary renal tumor in children Macro - large well-circumscribed mass soft, homogeneous, tan to gray, areas of hemorrhage, necrosis or cystic degeneration Micro - histology reveals some recapitulation of nefrogenesis - three components: blastema, stroma and epithelium - blastema: sheets of small blue cells - stroma: spindle cells (fibroblasts), heterologous elements (skeletal or smooth muscle, cartilage, osteoid, neurogenic tissue) - epithelium: abortive tubules and glomeruli Clinical presentation - palpable abdominal mass, fever, abdominal pain, hematuria, intestinal obstruction - generally good prognosis with appropriate therapy (nephrectomy and chemotherapy)