Comparing References

Impact of the achondroplasia FGFR3 mutation on growth: The effect from the activated FGFR3 on height development is interesting, partly from the background of the severity in the compromised growth of extremities in contrast to only marginally affected sitting height but also since the growth retardation may override height genetics (or epigenetics) of the background population. Thus adult height for published achondroplasia references is rather similar despite coming from varying ethnic groups and different time periods. Exceptions from a homogeneous adult height in the references may be dependent on younger age thus final height not attained. From this perspective any correlation between target height and height development is of interest and conflicting findings of positive or no correlation makes the question unclear, possibly the correlation might be found for sitting height whereas the maximal negative influence on leg length erradicates any background population influence. In individual cases we have seen improved sitting height in children with tall parents suggesting familial influence but that could not yet be confirmed on population level, e.g. Murdoch height data based on roughly 100 adult individuals and their parents. Smaller samples have, however, found a weak positive correlation (del Pino 2013; Merker 2018).

Another question is whether the FGFR3 mutation could affect the tempo of height development differently between populations even if adult height is similar. Comparison between achondroplasia height reference means at certain ages, e.g. 2, 5 and 9 yrs (avoiding pubertal ages that are much dependent on chosen technique of smoothing) and using Merker 2018 reference as comparator gives following (Horton and Tofts values visually read from graphs since tabled values were not available).