Pediatric Pathology I

Pediatric Pathology Overview

• Children exhibit distinct anatomical and physiological characteristics, impacting disease presentation compared to adults.
• Immune systems in children are less efficient, leading to increased susceptibility to infections.
• Children have a different range of tumors compared to adults.

Congenital Anomalies

• Malformation: Inherent abnormalities during the embryonic period (e.g., cleft lip), often multifactorial with genetic and environmental influences.
• Deformation: Extrinsic forces affecting normally developing structures, often due to restricted fetal movement during the fetal period.
• Disruption: Damage to a developing structure caused by destructive forces like amniotic bands, occurring during or after the fetal period.
• Approximately 3% of infants are born with a significant malformation.

Causes of Congenital Malformations

• Unknown causes account for 40-60% of cases.
• Genetic factors often involve chromosomal abnormalities, typically non-hereditary.
• Environmental influences include teratogens and infections.
• Multifactorial origins, combining genetic and environmental factors.

Teratogens

• Teratogens are agents that induce birth defects; examples include alcohol, thalidomide, and isotretinoin.
• About 1% of malformations can be attributed to teratogenic exposures.
• The timing of exposure during gestation influences the type and severity of malformations:
  • Embryonic stage: Most susceptible, impacts organogenesis.
  • Fetal stage: Affects growth retardation and brain development.

Perinatal Infections

• Severity of perinatal infections is influenced by timing of the infection during gestation.
• Two modes of transmission:
  • Ascending (Transcervical): Bacterial infections (e.g., Streptococcus agalactiae), leading to chorioamnionitis and neonatal pneumonia.
  • Transplacental: Hematogenous spread from mother, encompassing infections like Toxoplasmosis, Rubella, CMV, herpes, hepatitis B, HIV, and syphilis.
• Symptoms of transplacental infections can include fever, hepatosplenomegaly, chorioretinitis, pneumonia, cerebral calcifications, and developmental impairments.

Birth Weight Classifications

• Normal birth weight: Greater than 2,500 grams (5.5 lbs).
• Low birth weight (LBW): Less than or equal to 2,500 grams.
• Very low birth weight (VLBW): Less than 1,500 grams (3.3 lbs).

Prematurity and Associated Conditions

• Prematurity: Defined as birth occurring before term, which can lead to fetal edema due to inadequate oxygen supply.
• Hydrops categories:
  • Immune Hydrops: Result of antibody-induced hemolytic disease in newborns.
  • Nonimmune Hydrops: The most common form, caused by other factors.