Paediatric Diseases And Conditions Of Infancy And Childhood Notes

Paediatric Diseases

As mentioned in the foregoing discussion, many diseases affecting infancy and childhood are genetic or developmental in origin. Here, other diseases affecting the period from birth to puberty are discussed under the heading of paediatric diseases.

Read And Learn More: General Pathology Notes

This period is conventionally subdivided into 4 stages:

1. Neonatal period: birth to first 4 weeks
2. Infancy: first year of life
3. Early childhood: 1-4 years
4. Late childhood: 5-14 years

Each of these four stages has distinct anatomic, physiologic and immunologic development compared to adults and, therefore, has different groups of diseases unique to particular age groups.

Non-Neoplastic Conditions Of Infancy And Childhood

A few general comments can be made about proneness to different diseases at various stages of
children:

• Neonatal period: Neonatal period is the period of continuation of dependent intrauterine foetal life to an independent postnatal period.
  • Therefore, this is the period of maximum risk to life due to perinatal causes (for example, Prematurity, Low birth weight, Perinatal infections, Respiratory distress syndrome, Birth asphyxia, Birth trauma etc) and congenital anomalies.
  • If adequate postnatal medical care is not provided, neonatal mortality is high.
  • Neonatal mortality in the first week after birth is about 10 times higher compared to the second week and shows improvement with every passing week at this stage.
• In infancy: The major health problems are related to congenital anomalies, hydrops, infections of the lungs and bowel, and sudden infant death syndrome (often during sleep).
• Young children from 1-4 years:  Are exposed to a higher risk of sustaining injuries, and manifesting certain congenital anomalies. Some malignant tumours are peculiar to this age group.
• Older children from 5-14 years: Too have a higher risk of injuries from accidents and have other problems related to congenital anomalies and certain malignant tumours at this age.

Thus, the hazardous effects of congenital anomalies are a common denominator for all age groups from birth to adolescence. Two conditions—foetal hydrops and sudden infant death syndrome, are briefly discussed below.

2. Foetal Hydrops:

Foetal hydrops refers to oedema fluid accumulation in the foetus during intrauterine growth. The fluid accumulation may be generalised or localised to an organ or a cavity. Foetal hydrops is of two types: immune and non-immune.

• Immune hydrops:  This is also called as erythroblastosis foetal or haemolytic disease of newborn. It is due to the incompatibility of blood group between the mother and the developing fetus. It is often due to Rh incompatibility while infrequently ABO incompatibility may also cause it.
• Non-immune hydrops:  Major causes for non-immune hydrops are cardiovascular defects (for example, Malformations), chromosomal anomalies (for example, Turner syndrome, trisomies) and foetal anaemia (for example,α-thalassaemia, parvovirus infection).

Morphologic Features:

• The main findings in foetal autopsy are as under:
• A variable amount of fluid accumulation in the foetus may be generalised or localised.
• Depending upon the extent of fluid accumulation, the baby may be stillborn, die within a few days, or recover.
• Congenital anomalies due to chromosomal abnormalities.
• In hydrops due to foetal anaemia, both foetus and placenta are pale.
• Cardiac anomalies may be present.
• Parvovirus infection may be associated with compensatory erythroid hyperplasia and characteristic findings in developing erythroid cells.
• Hepatosplenomegaly is frequently present.
• Due to haemolysis, kernicterus is present and may bilirubin may be deposited in the basal ganglia and brain stem.

Sudden Infant Death Syndrome (Sids):

SIDS or crib death is the unexplained death of an infant (under one year), usually during sleep. Although the cause is not known, a few risk factors have been found associated with SIDS:

• Brain defects i.e. the portion of the brain that controls sleep and arousal has not developed fully.
• Low birth weight babies
• Recent respiratory infection
• Sleep posture for example, Sleeping on the side or on the stomach that the baby may have difficulty in breathing
• Prematurity
• Maternal risk factors for example, Younger age of the mother, smoking, use of alcohol or drugs, inadequate perinatal care
• Other risk factors, for example, Family history of crib death, passive smoke in the environment.

Non-neoplastic Conditions of infancy and Childhood:

• Distinct conditions affect during growing years in children: in the neonatal period (perinatal causes), infancy (congenital anomalies), children 1- 4 years (malignant tumours), and children 4-14 years (malignant tumours).
• Foetal hydrops is an accumulation of variable amount of oedema fluid in the foetus. It may be immune (more common) due to blood group incompatibility between mother and foetus, or non-immune (less common).
• Sudden infant death syndrome or crib death is death of infant due to unexplained cause.
• However, a few risk factors pertaining to the baby, mother and environment are implicated.

Tumours Of Infancy And Childhood

Tumours of infancy and childhood comprise 2% of all malignant tumours but they are the leading cause of death in this age group exceeded only by accidents.

Benign tumours are more common than malignant tumours but they are generally of little immediate consequence.

Another aspect requiring consideration here is the difficulty in differentiating benign tumours from tumour-like lesions.

Histogenesis:  Histogenetic evolution of tumours at different age groups takes place as under:

1. Some tumours have probably evolved in utero and are apparent at birth or in the immediate postnatal period. Such tumours are termed developmental tumours.
2. Many other tumours originate in abnormally developed organs and organ rests; they become
   apparent subsequently and are termed embryonic tumours.
3. In embryonic tumours, the proliferation of embryonic cells occurs which have not reached the differentiation stage essential for specialised functions i.e. the cells proliferate as undifferentiated
   or as partially differentiated stem cells and an embryonal tumour (embryoma or blastoma) is formed.
4. Tumours of infancy and childhood have some features of normal embryonic or foetal cells in them which proliferate under growth-promoting influence of oncogenes and suffer from mutations which make them appear morphologically malignant.
5. Under appropriate conditions, these malignant embryonal cells may cease to proliferate and transform into non-proliferating mature differentiated cells for example, A Neonatal neuroblastoma may mature and differentiate into benign ganglioneuroma.
6. Tissues in foetal sacrococcygeal teratoma may mature with age to adult tissues and is assigned a better prognosis.
7. Thus, normal somatic cell maturation and neoplastic development in embryonal tumours represent two opposite ends of ontogenesis, with the capability of some such tumours to mature and differentiate to turn benign from malignant.

Benign Tumours And Tumour-Like Conditions

Many of the benign tumours seen in infancy and childhood are actually the growth of displaced cells and masses of tissues and their proliferation takes place along with the growth of the child.

Some of these tumours undergo a phase of spontaneous regression subsequently a feature usually not seen in true benign tumours. While some consider such lesions as mere ‘tumour-like lesions or malformations’, others call them benign tumours.

A few such examples are as under:

• Hamartomas:  Hamartomas are focal accumulations of cells normally present in that tissue but are arranged in an abnormal manner i.e. though present at normal site they do not reproduce normal architecture identical to adjacent tissues.
• Choristoma (heterotopia):  Choristoma or heterotopia is a collection of normal cells and tissues in aberrant locations for example, Heterotopic pancreatic tissue in the wall of the small bowel or stomach.

A list of common benign tumours and tumour-like lesions is presented given in table.

Malignant Tumours

Cancers of infancy and childhood differ from those in adults in the following respects:

1. Sites:  Cancers of this age group more commonly pertain to the haematopoietic system, neural tissue and soft tissues compared to malignant tumours in adults at sites such as the lung, breast,
   prostate, colon and skin.
2. Genetic basis:  Many of paediatric malignant tumours have underlying genetic abnormalities.
3. Regression:  Foetal and neonatal malignancies have a tendency to regress spontaneously or to mature.
4. Histologic features:  These tumours have unique histologic features in having primitive or embryonal appearance rather than pleomorphic-anaplastic histologic appearance.
5. Management:  Many of paediatric malignant tumours are curable by chemotherapy and/or radiotherapy but may develop a second malignancy.

Common paediatric beings’ tumours and tumour-like lesions:

Common paediatric malignant tumours:

A few generalisations can be drawn about paediatric cancers:

• In infants and children under 4 years of age: the most common malignant tumours are various types of blastomas.
• Children between 5 and 9 years of age: haematopoietic malignancies are more common.
• In the age range of 10-14 years (prepubertal age): soft tissue and bony sarcomas are the prominent tumours.
• Small round cell blue cell tumours (SRBCTs) are a group of tumours in children which have histologic features of small round cells having high N/C ratio.
• Since they have fairly identical morphology, immunohistochemical stains are helpful in assigning them cell of origin.
• Common examples are:
  • Ewing’s sarcoma/PNET (primitive neuroectodermal tumour), Lymphomas, Retinoblastoma, Neuroblastoma, Wilms’ tumour, Hepatoblastoma, Medulloblastoma, Rhabdomyosarcoma, Desmoplastic SRCT, Small cell osteosarcoma.

Based on this overview, the classification of common paediatric malignant tumours at different age groups is presented.

Tumours of Infancy and Childhood:

• Tumours of infancy and childhood may evolve during intrauterine life (developmental tumours), or maybe embryonic tumours arising from the fully or partially differentiated stage or undifferentiated stem cells.
• Small round blue cell tumours are malignant tumours in children having a high N/C ratio and include various blastomas.
• Common examples of benign paediatric tumours are haemangioma, lymphangioma, sacrococcygeal teratoma and fibromatosis, besides a few possible tumours (naevi, liver cell adenoma).
• Common malignant tumours in children under 4 years of age are acute leukaemias, blastomas/embryomas (neuroblastoma, hepatoblastoma, retinoblastoma, nephroblastoma mor Wilms’ tumour), gliomas and teratomas.
• Common malignant tumours in older children (beyond 4 and under 14 years of age) are lymphomas, soft tissue sarcomas, osteogenic sarcoma, Ewing’s sarcoma and thyroid cancer.