Monitoring of growth is a major component of anticipatory guidance in pediatrics,and its abnormalities guide the physician to various categories of disease. It is important to monitor head circumference in addition to height and weight, even beyond the 36 months included on standard charts, because disproportion among height, weight, and head circumference is pivotal in separating nutritional problems from congenital disorders.

For infants and young children with growth delay (failure to thrive), a disproportionately small head circumference can indicate abnormal brain development as seen in fetal alcohol or many genetic syndromes. A head circumference that is closer to the normal range than the length and weight may indicate “head-sparing;”such measures often indicate psychosocial or nutritional deprivation with preferential routing of calories to cerebral development. A normally expanding, proportionately larger head circumference often occurs in children with developmental disabilities like fragile X syndrome, cerebral gigantism, or certain autism spectrum disorders– these disorders may alter the programmed death or “pruning” of brain cells that is so critical for normal development.

The chapters in this section focus on children with constitutional causes of growth deficiency, and it is critical to distinguish those that are proportionately small (see Chapter 10) from those with disproportionate short stature (skeletal dysplasia ordwarfism – see Chapter 11). Single gene causes predominate in both categories, with the congenitally small having syndromes analogous to the chromosome disorders discussed in Chapter 7 and the skeletal dysplasias manifesting very different signs that include large heads with frontal bossing, short limbs, and small or deformed chests and spines.