Scheuermann disease [OMIM number 181440] is the most common cause of structural 
kyphosis in adolescence. Segregation analysis using a model with gender effects 
was applied to 90 pedigrees from Barnaul (West Siberia, Russia) ascertained 
through a proband with Scheuermann disease. The transmission probability model 
was used to detect major gene effect. A significant contribution of a major gene 
to the control of the pathology was established. Inheritance of the disease can 
be described within the framework of a dominant major gene diallele model. 
According to this model, Scheuermann disease should never occur in the absence 
of the mutant allele. All male carriers of the mutant allele develop the 
disease, while only a half of female carriers manifest it. We found a high 
frequency of idiopathic scoliosis in the families with Scheuermann disease (0.08 
vs. 0.01-0.02 in general population). We also observed a succession of 
idiopathic scoliosis and Scheuermann disease in consecutive generations. The 
familial aggregation of these two spinal pathologies in the present sample may 
indicate a genetic unity of Scheuermann disease and idiopathic scoliosis.