Chapter 7. Pediatric Pathology

Although many conditions that affect adults also affect children, pediatric pathology includes many conditions found only in patients younger than 18 years of age. This chapter will address many of these conditions.

One group of conditions involving the infant population is congenital anomalies. Several terms are important to remember when discussing congenital anomalies. A malformation is a congenital anomaly due to an intrinsic defect in development. A disruption occurs when a normally developing organ is secondarily damaged by another process. For example, in amniotic band syndrome, a fragment of the amniotic membrane wraps around a portion of the body and damages or amputates it. A deformation is an abnormal development of an organ due to an extrinsic process. A sequence is a collection of several anomalies, all of which are due to one malformation, disruption, or deformation. For example, Potter sequence is due to oligohydramnios and includes flat facies, small chest, hypoplastic lungs, club foot (talipes equinovarus), and nodules in the amniotic sac. Finally, a syndrome is a group of related anomalies. Common congenital anomalies include clubfoot, patent ductus arteriosus, ventricular septal defect, and cleft lip or cleft palate. Although most congenital anomalies are diagnosed during infancy, they are present and can cause complications into adulthood.

This chapter will discuss causes of congenital anomalies and major congenital anomalies by organ system. Also discussed are conditions diagnosed in the pediatric population such as prematurity, perinatal infections, hydrops fetalis, sudden infant death syndrome (SIDS), and select pediatric tumors, including neuroblastoma and Wilms tumor.

Overview: The causes of congenital anomalies are genetic, environmental, and multifactorial; however, the etiology of many congenital anomalies is unknown. Two common environmental causes of congenital anomalies are nicotine and maternal diabetes mellitus.

• Nicotine: Use of nicotine when pregnant predisposes the mother to a high risk for spontaneous abortion, placental abruption, premature labor, or placental abnormalities.
• Maternal diabetes mellitus: Predisposes to a large-for-gestational-age fetus, neural tube defects, and neonatal hypoglycemia. The most common associated anomalies are cardiac. The most severe associated disorder is caudal regression syndrome (also referred to as “mermaid syndrome”), which causes fused, malformed lower extremities and sacral agenesis.

Cardiac anomalies

Ventricular septal defect, atrial septal defect, patent ductus arteriosus, and tetralogy of Fallot are only a few of many cardiac congenital anomalies (see Chapter 10).

Central nervous system anomalies: Anencephaly and holoprosencephaly are only two of many congenital anomalies of the central nervous system (see Chapter 11).

Respiratory system congenital anomalies: Although there are other congenital anomalies of the respiratory system, only pulmonary sequestration and foregut cysts will be discussed below.

Pulmonary sequestration

• Basic description: Discrete region of lung tissue that has no connection to the airway.
• Forms
  • Extralobar sequestration: Discrete mass of lung tissue occurring outside the lungs. Infants can present with a mass lesion.
  • Intralobar sequestration:...