Short stature

What it is

Short stature is the common feature of three conditions that are asked about together: Turner syndrome, achondroplasia and Prader Willi syndrome. In achondroplasia it is put as short stature below the 3rd percentile. In Turner syndrome short stature, from the SHOX gene, together with ovarian dysgenesis, is the most consistent finding.

Causes and risk

Achondroplasia is autosomal dominant, with a defect in FGFR-3. Prader Willi syndrome is sporadic, from a paternal derived deletion 15q11-13 in 80% or maternal UPD in 20%; its short stature, central obesity and hypogonadism are secondary to hypothalamic and pituitary dysfunction. Before the syndromes come the normal variants. In familial short stature both sexes are equally affected, length at birth is normal, the family history is of short stature with one or both parents short, height velocity and puberty are normal, bone age equals chronological age and both stand above height age, and the final height is short but normal for the target height; the growth velocity is low-normal throughout childhood and adolescence, the height percentile sits in the range of the mid-parental height, and that target height is the bi-parental height plus or minus 2SD, that is 10 cm. In constitutional delay in growth the child is more often a boy, length at birth is normal but starts falling below the 5th centile in the first 3 years of life, the family history is of delayed puberty, the parents are of average stature, height velocity is normal, puberty is delayed, chronological age stands above bone age which equals height age, and the final height is normal; the downward shift begins between 4-6 months and 24-36 months and then parallels a lower percentile, usually the 5th. Idiopathic short stature is a diagnosis of exclusion: the height percentile is below the range of the mid-parental height, there is no evidence of underlying disease, and bone age equals chronological age.

Read off the height on the growth chart, short stature points to Turner syndrome and to constitutional delay of growth and puberty, while tall stature points to Klinefelter syndrome. The dysmorphic features that point to Turner syndrome are a webbed neck, short stature and a low hairline, and a family history of late puberty points to constitutional delay of growth and puberty instead. A growth velocity that falls off is read as either peripubertal growth slowing or pathologic growth due to an underlying condition.