Identification of a novel heterozygous IGF1 splicing mutation in a large kindred with familial short stature.

BACKGROUND/AIMS: Insulin-like growth factor (IGF)-I is critical for normal human growth. Extremely rare homozygous mutations of the IGF1 gene severely impair intrauterine growth, intellectual development and postnatal growth. CASE/
METHOD: A young male presented with postnatal growth retardation (-4.0 height SDS). His serum IGF-I concentration was low (115 µg/l, -2.21 SDS) and increased minimally to 130 µg/l (-1.82 SDS) on GH therapy, and he was analyzed for defect(s) in the GH-IGF-I axis. Severe short stature could be traced back several generations.
RESULTS: From the proband and 4 other severely short-statured family members, two novel, heterozygous, variants were identified in the IGF1 gene: c.207G>A in exon 3 and c.402+1G>C in the donor splice site of intron 4. The IGF1 gene was normal in 11 normal stature family members, and, interestingly, in 5 other short-statured family members. Study of IGF1 mRNA indicated c.402+1G>A induced splicing out of exon 4, leading to a predicted frameshift and protein truncation.
CONCLUSIONS: A novel heterozygous IGF1 splicing variant is associated with familial short stature in an extended family. Although it remains unclear whether this heterozygous mutation is the cause of the growth failure, the extreme rarity of IGF1 gene defects makes these cases of considerable interest.