Congenital malformations - Edocr

Chapter 50
Hemihyperplasia and
Overgrowth Disorders
PRAVEEN KUMAR
INTRODUCTION
An overgrowth disorder is defined as a condition
in which there is localized or generalized
excessive growth and physical development for
the age and sex of the individual. 1 Weaver classified
overgrowth syndromes in the following
three broad categories:
1. Generalized overgrowth syndromes which
include conditions in which all or most parameters
of growth and physical development
are in excess of two standard deviations
above the mean for the person’s age and
sex such as, Sotos syndrome. The conditions
in this category could have either prenatal
or postnatal onset of overgrowth.
2. Regional overgrowth disorders include
those in which excessive growth is confined
to one or a few regions of the body such as,
isolated hemihypertrophy; these disorders
also have their onset in either the prenatal
or postnatal period.
3. Parameter-specific overgrowth disorders in
which a single growth parameter is in excess
of normal such as obesity or tall stature; most
of these disorders have a postnatal onset.
Most overgrowth disorders seen in a neonate
have prenatal onset and will fall into either the
generalized or regional overgrowth disorder category.
The following discussion will review the
approach to the evaluation of a neonate with
generalized or regional overgrowth disorders
and does not include large for gestational age
infants of diabetic mothers.
EPIDEMIOLOGY/ETIOLOGY
The true prevalence of overgrowth disorders
among neonates is not clearly established. The
overgrowth syndromes are rare and only a handful
of cases have been reported for some syndromes.
The incidence of Beckwith-Wiedemann
syndrome (BWS), one of the most common overgrowth
syndromes, is reported to be 1:14,000
births. 2,3 A recent series of observations have
suggested a link between assisted reproduction
and imprinting disorders such as BWS and
Angelman syndrome. 4 A retrospective study reported
a risk of BWS in an in vitro fertilization
population to be approximately 1 in 4000. 5 Several
population-based studies have reported a prevalence
rate of hemihypertrophy to range from 1 in
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