Osteogenesis imperfecta (OI) is a heterogeneous group of inherited disorders of 
bone formation, resulting in low bone mass and an increased propensity to 
fracture. It exhibits a broad spectrum of clinical severity, ranging from 
multiple fractures in utero and perinatal death, to normal adult stature and low 
fracture incidence. Extra-skeletal features of OI include blue sclera, hearing 
loss, skin hyperlaxity, joint hyperextensibility, and dentinogenesis imperfecta. 
The proα1(I) and proα2(I) chains of collagen 1 are encoded by the COL1A1 and 
COL1A2 genes, respectively; quantitative or qualitative defects in type I 
collagen synthesis usually manifest as types of OI or some sub-types of EDS. The 
majority of patients (about 90%) with a clinical diagnosis of OI have a mutation 
in the COL1A1 or COL1A2 genes, which shows an autosomal dominant pattern of 
inheritance. Six other genes, CRTAP, LEPRE1, FKBP10, PP1B, SP7/Osterix (OSX), 
and SERPINH1, are associated with autosomal recessive forms of OI. However, 
other, rare phenotypes have also been described. There are many differential 
diagnoses of the short, syndromic child, including chromosomal, single gene, and 
multifactorial causes. However, one condition of particular relevance in the 
context of this report is the Russell-Silver syndrome (RSS). As originally 
described, the RSS is a very specific condition. However, it has subsequently 
become an umbrella term for a heterogeneous group of conditions presenting with 
short stature and triangular shape to the face. A significant proportion of 
these are now believed to be due to imprinting defects at 11p15. However, the 
cause in many cases remains unknown. We describe two cases with a phenotypic 
overlap between OI and RSS who both have COL1A1 mutations. Thus, a type 1 
collagenopathy should be considered in the differential diagnosis of syndromic 
short stature.