VCFS is caused by a deletion of 22q11.2 One of our 2 copies of chromosome 22 loses 40 genes
Genome at 22q11.2 Most individuals with VCFS are missing 40 genes on one copy of chromosome 22. One or more of these genes may contribute to normal growth or normal growth velocity as regulated by hormones or some other timing mechanism DGCR6 PRODH2 DGCR5 CALS2 IDD TSK-P TSK-1 DGS-I GSCL CTP CTLD HIRA NLVCF VCF-A UFD1L CDC45L TMVCF PNUTL GP1BΒ TBX-1 WDR14 TRXR2 COMT ARVCF T10 DGCR8 HTF9C RANBP1 KIAA1292 VCF-B VCF-C NOGOR PRODH2-p DGCR6-L USP18-p ZNF74 SRECII VCF-D PCQAP SERPIND1 SNAP29 CRKL VCF-E LZTR VCF-F VCF-G P2RXL1 SLC7A4 R R R R R Low copy repeats (4)Pseudogenes (8)Genes (40)
Many (most) children with VCFS have low weight and short stature when compared to the CDC growth charts that are normed for the general population. This is especially true for infants, toddlers and young children.
Is it appropriate to compare children with VCFS (people missing 40 genes) to growth velocity curves that are normed for people who do not have VCFS (who are not missing 40 genes)?
Research has already demonstrated that muscle mass in people with VCFS is reduced for at least some parts of the body. There are fewer muscle fibers and the each muscle fiber is smaller than normal.
Muscle is a dense and heavy tissue that accounts for a high percentage of body weight.
Weight proportion is different in VCFS than in the general population VCFS baby with failure-to- thrive based on CDC data subcutaneous fat True failure-to-thrive
There are growth curves specific to other syndromes such as Down syndrome and Williams syndrome.
Method Retrospective data from 1,085 patients with VCFS who had multiple documented heights and weights All data pooled according to age and sex Presence or absence of heart anomalies assessed as variables Presence or absence of feeding difficulties, G- tubes, etc., were assessed as variables
VCFS Growth Chart, males, length and weight, 0 - 36 months of age
VCFS Growth Chart, Length and Weight, boys 0 - 36 months of age compared to CDC norms used for the general population
Comparisons The presence of heart anomalies was not a factor in long- term growth except in early infancy and in severe cases with pulmonic stenosis/atresia Males reached averaged parental heights, females tended to fall slightly short In childhood, weight was low compared to height (typically between the 10 th to 25 th centile) according to CDC norms Following puberty, weight was proportionate to height Growth velocity in VCFS differs from the general population
Comparisons Head circumference growth was independent of somatic growth and weight Early feeding difficulties were not predictive of short stature or low weight as an adolescent or adult The presence of alternative feeding in infancy did not increase linear growth velocity In other words, the effects of the deletion was the major influence on growth
The overwhelming majority of people with chromosomal rearrangements involving multiple genes have abnormal growth patterns, and the large majority of them have growth velocities that do not look like the general population. Comparing people with genetic or chromosomal rearrangements to growth charts based on the general population in order to recommend treatment is not appropriate.
Therefore, treating children with VCFS in a manner that is designed to have them fit the norms for the general population is inappropriate.