Pediatric Pathology

“Children are not merely little adults, and their diseases are not merely variants of adult diseases”

Cause of Death Related with Age UNDER 1 YEAR Congenital malformations, deformations, and chromosomal anomalies Disorders related to short gestation and low birth weight Sudden infant death syndrome (SIDS) Newborn affected by maternal complications of pregnancy Newborn affected by complications of placenta, cord, and membranes Respiratory distress of newborn Accidents (unintentional injuries) Bacterial sepsis of newborn Intrauterine hypoxia and birth asphyxia Diseases of the circulatory system

1–4 YEARS Accidents and adverse effects Congenital malformations, deformations, and chromosomal abnormalities Malignant neoplasms Homicide and legal intervention Diseases of the heart (Excludes congenital heart disease) Influenza and pneumonia

5–14 YEARS Accidents and adverse effects Malignant neoplasms Homicide and legal intervention Congenital malformations, deformations, and chromosomal abnormalities Suicide Diseases of the heart

15–24 YEARS Accidents and adverse effects Homicide Suicide Malignant neoplasms Diseases of the heart

Congenital Anomalies morphologic defects that are present at birth the exact cause remains unknown in at least half to three quarters of the cases common known causes of congenital anomalies: – Genetic – Environmental – Multifactorial

Genetic Anomalies that are known to be genetic in origin can be divided into two groups: – Those associated with chromosomal aberrations – Those arising from single-gene mutations (“mendelian disorders”) trisomy 21 (Down syndrome) is the only one that approaches a birth frequency of greater than 10 in 10,000 total births

Fetal Hydrops accumulation of edema fluid in the fetus during intrauterine growth Two Causes: – Immune – Nonimmune

Immune Hydrops Antibody induced hemolytic disease in the newborn caused by blood group incompatibility between mother and fetus. Rh and ABO blood group antigens, most common antigens.

Nonimmune Hydrops Cardiovascular Defetcs. a. structural b. functional Chromosomal anomalies. a. 45,X karyotype (Turner syndrome) b. Trisomies 21 and 18 - the basis of this is the presence of underlying structural cardiac anomalies Fetal Anemia due to causes other than Rh and ABO incompatibility.

Fetal Anemia Homozygous alpha thalassemia – most common cause of HF in Southeast Asia Transplacental infection e.g. Parvovirus B19 – Virus gains entry into erythroid precursors (normoblasts), where it replicates. – Leads to erythrocyte maturation arrest and aplastic anemia – Parvoviral intranuclear inclusions can be seen within circulating and marrow erythroid precursors

Pathogenesis of Hydrops Severe anemia Hepatic extramedullary hematopoeisis Decreased prdtn of plasma proteins Decreased oncotic pressure

Pathogenesis of Hydrops Congestive heart failure Increased central venous pressure Increased capillary hydrostatic pressure

Pathogenesis of Hydrops Severe tissue hypoxia Endothelial cell damage Capillary leak of fluid & protein

BENIGN TUMORS AND TUMOR- LIKE LESIONS Hemangioma – are the most common tumors of infancy – Types: Cavernous Capillary

Teratomas Tumor with at least 2 out of 3 germ layers – benign, well-differentiated cystic lesions (mature teratomas) – indeterminate potential – unequivocally malignant teratomas

MALIGNANT TUMORS incidence in children younger than age 10 years include (1) leukemia (principally acute lymphoblastic leukemia) (2) neuroblastoma (3) Wilms tumor (4) hepatoblastoma (5) retinoblastoma

(6) rhabdomyosarcoma (7) teratoma (8) Ewing sarcoma posterior fossa neoplasms—principally (9) juvenile astrocytoma (10) medulloblastoma (11) ependymoma

Neuroblastoma the most common extracranial solid tumor of childhood most frequently diagnosed tumor of infancy one case in 7000 live births median age at diagnosis is 18 months 40% of cases are diagnosed in infancy Most cases occur sporadically most (60% to 80%) children present with stage 3 or 4 tumors (unresectable)

Wilms Tumor approximately 1 in every 10,000 children in the United States most common primary renal tumor of childhood fourth most common pediatric malignancy in the United States 95% of tumors occur before the age of 10 years Involves mutation of the WT1 gene