Costello syndrome is a rare condition due to heterozygous germline mutations in 
the proto-oncogene HRAS. It affects multiple organ systems and includes severe 
failure-to-thrive, short stature, and macrocephaly. The goal of this study was 
to develop Costello syndrome-specific growth curves. We collected height, 
weight, and head circumference (OFC) measurements from 94 individuals (45 males 
and 49 females). Their HRAS mutation spectrum reflects previously published 
cohorts, with p.G12S in 77.7%. Participants received medical care, therefore our 
data does not reflect natural history per se, but rather growth with nutritional 
support. Due to limited cohort size, we analyzed data from males and females 
together. Weight-for-age data included 417 separate measurements from 80 
individuals age 0-36 months, and 585 measurements from 82 individuals for age 
0-10 years. Height-for-age data were derived from 391 measurements from 77 
individuals age 0-36 months, and 591 measurements from 90 individuals age 0-10 
years. Measurements obtained after growth hormone exposure in 15 individuals 
were excluded in this analysis. The OFC curve was derived from 221 measurements 
from 55 individuals age 0-36 months. Centiles (5th, 50th, and 95th) were 
estimated across the age continuum for each growth parameter, and compared to 
gender-specific curves for average stature individuals. The resulting curves 
demonstrate very slow weight gain in the first 2 years. Short stature is seen in 
many, but after age 4 years the 95th centile for height falls within the low 
normal range for average stature children. Head circumference curves largely 
overlap those for average stature, reflecting relative macrocephaly.