Blount's disease or congenital tibia vara is a clinical entity characterized by 
tibia bowing, tibia torsion, and beaking of the medial tibia metaphysis on plain 
radiograph. In our environment, burnt-out rickets patients with biochemical and 
radiological diagnosis of rickets who after treatment still have residual bone 
changes despite normal bone biochemistry) can also present with similar clinical 
and radiological features as Blount's disease. However, certain biochemical 
variations, including antioxidants, may serve as a basis for differentiation 
between these two disorders. The serum levels of calcium, inorganic phosphate, 
zinc, copper, and alkaline phosphatase in 15 patients (10 females and five 
males) aged between two- and five years (mean 3.8 +/- 1.1 (SD)) with clinical 
and radiological features of Blount's disease were determined. The mean weight 
of the patients with Blount's disease was 14.0 +/- 2.4 kg (range: 11.5-16.3 kg). 
Fifteen subjects (nine females and six males) matched for age and sex without 
clinical features of any metabolic bone and/or nutritional diseases who were 
attending the surgical outpatient clinic served as control subjects. The serum 
concentrations of inorganic phosphate and calcium, though lower in patients with 
Blount's disease compared with controls, did not reach statistical significance. 
Alkaline phosphatase activity was increased in the serum of all patients with 
Blount's disease. In addition, there was an observed significant reduction in 
serum concentration of zinc (P < 0.03) compared to the control subjects. As for 
calcium level, the concentration of serum copper in Blount's patients was 
reduced, but this was not statistically significant. These biochemical 
observations, especially those of the antioxidant micronuent zinc, may serve as 
a basis for the differentiaion of the sometimes clinically inseparable disorders 
of Blount's and rckets and may aid in early differential diagnosis, appropriate 
treatment as well as prevention of complications.