The etiology of idiopathic scoliosis remains unknown. The condition results in a 
characteristic deformity of the spine and surrounding tissues. Both Types I and 
II collagen are important constituents of the affected tissues, and thus 
defective collagens are reasonable candidates for the primary abnormality in 
adolescent idiopathic scoliosis (AIS). Direct analyses of the amount and 
solubility of collagen have revealed differences between normal individuals and 
those with AIS. However, these changes may be secondary to the mechanical 
effects of the spinal deformity. Segregation analysis was done of genetic 
markers linked to the structural genes encoding Types I and II collagen to test 
these candidate loci in four pedigrees with dominantly inherited AIS. In one 
pedigree, markers linked to both of the Type I collagen loci (COL1A1 and COL1A2) 
were found to be inherited independently of the abnormal phenotype. Two 
pedigrees were discordant at one of the Type I loci. The condition also 
segregated independently of the locus for Type II collagen (COL2A1) in three 
pedigrees. This is evidence against idiopathic scoliosis generally being caused 
by mutations in the Types I and II collagen genes.