Abstract
In general population, there are three phases in the human growth curve: infancy, childhood and puberty, with different main factors involved in their regulation and mathematical models to fit them. Achondroplasia children experience a fast decreasing growth during infancy and an "adolescent growth spurt"; however, there are no longitudinal studies that cover the analysis of the whole post-natal growth. Here we analyse the whole growth curve from infancy to adulthood applying the JPA-2 mathematical model. Twenty-seven patients, 17 girls and 10 boys with achondroplasia, who reached adult size, were included. Height growth data was collected from birth until adulthood. Individual growth curves were estimated by fitting the JPA-2 model to each individual's height for age data. Height growth velocity curves show that after a period of fast decreasing growth velocity since birth, with a mean of 9.7cm/year at 1 year old, the growth velocity is stable in late preschool years, with a mean of 4.2cm/year. In boys, age and peak height velocity in puberty were 13.75years and 5.08cm/year and reach a mean adult height of 130.52cm. In girls, the age and peak height velocity in puberty were 11.1years and 4.32cm/year and reach a mean adult height of 119.2cm. The study of individual growth curves in achondroplasia children by the JPA-2 model shows the three periods, infancy, childhood and puberty, with a similar shape but lesser in magnitude than general population.
Highlights
Achondroplasia (ACH), an autosomal-dominant disorder, is the most common form of inherited severe and disproportionate short stature, occurring with birth prevalence between 1 in 10,000 and 1 in 30,000 live births [1]
In general population, there are three phases in the human growth curve: infancy, childhood and puberty, with different main factors involved in their regulation and mathematical models to fit them
There are three phases in the growth curve: infancy, childhood and puberty. These periods are the additive effect of various biological processes with different main factors involved in their regulation, as well as different mathematical models to fit them [4, 5]
Summary
Achondroplasia (ACH), an autosomal-dominant disorder, is the most common form of inherited severe and disproportionate short stature, occurring with birth prevalence between 1 in 10,000 and 1 in 30,000 live births [1]. It is caused by a gain of function mutation in the type 3 fibroblast growth factor receptor gene (FGFR3), located on chromosome 4p16.3 that leads to abnormal endochondral ossification [2, 3]. The rapidly decelerating growth in the first 2 years of life is a prolongation of foetal growth This is the infancy component, which appears to be mainly nutritionally determined and guided by thyroid hormones. The final component of the human growth curve is puberty, in which sexual hormones initiate the pubertal spurt and subsequently lead to the end of growth, through the closure of the epiphysis [4, 5]
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