Body Proportions

by Jane

The body proportions in my 15 years old daughter seem to be disturbed. Her target height is 161 cm, but she has reached a height of 172 cm, even though we are not a tall family.
Her arm-span is 161 cm and her leg-length is 100 cm (she appears to have reduced upper to lower segment ratio).

Doc, what could possibly cause these body proportions in a teenager? Has this something to do with late or early puberty? We have not consulted any other doctor about this yet.
Kindly advise.

The Expert, Ren Chats Answers

Genetic Variant:
Child growth and development is a classic polygenic expression. A variety of complex biological and environmental factors influence changes in DNA that alter gene activity, the genetic variants. It is genetic variation that gives a distinct look to each person such as hair-color, height, body shape, etc.

Adult human stature is influenced by genetic variants in more than 150 specific positions on a chromosome, called locus. Consequently, normal stature varies widely but certain body proportions are generally accepted as normal in growth of a child (See Fig. Body Proportions given above).

Individual variations in growth pattern:
A single height measurement is of no value in detecting growth disorder. Serial height and weight measurements over time documented on a growth chart are required to evaluate individual rate of growth. It is the rate of growth that differentiates the normal from abnormal growth. Tall stature is defined as Two Standard Deviation from the individual pattern of growth, or above 97th percentile for the age (see Fig. Abnormal Body Proportions In A 15 Yr. Old given above).

The measurements given here do not tally:
The height and long leg length indicate tall stature, whereas the short arm span points towards short-limb dwarfism. Short stature is typically associated with upper to lower segment ratio of above 1.3. But according to given measurements, your daughter’s upper to lower segment ratio is only 0.7, which is consistent with abnormal tall stature (see Fig. Body Proportions given above).

Can it be Skeletal Dysplasia?
No.
For two reasons an inborn abnormal bony structure, medically known as skeletal dysplasia, also does not fit with the parameters provide.
1. Skeletal dysplasia is usually accompanied with short stature.
2. Being an outcome of genetic mutation, skeletal dysplasia presents early in childhood.
Still, in view of abnormal body proportions noted, skeletal dysplasia and rare growth disorder should be considered. Small upper segment could be due to diminished vertebral growth (see Fig. Leg Length And Sitting Height Ratio given above). Nevertheless, an error in the measurements taken cannot be ruled out.

Related pages of interest:

1. Increased Arm Span To Height Ratio

2. Short Arm Span in a 9 Year Old

3. Body Ratios

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