BACKGROUND: Legg-Perthes disease is associated with ischemia of the capital 
femoral epiphysis in children. Thrombophilia has been implicated as a potential 
cause of the condition, and screening of patients with Legg-Perthes disease for 
thrombophilia has been recommended. We analyzed the value of screening for 
inherited thrombophilia in patients with Legg-Perthes disease by examining the 
association between Legg-Perthes disease and abnormalities in the thrombotic 
pathway.
METHODS: A random series of consecutive patients with Legg-Perthes disease were 
prospectively enrolled in this study. Assays for the detection of factor-V 
Leiden mutation and the plasma concentrations of protein C, protein S, 
antithrombin III, and lipoprotein (a) were performed on plasma samples from 
children with Legg-Perthes disease, and the results were compared with those for 
pooled plasma from normal controls. Plasma concentrations below the 95% midrange 
of the control values were classified as protein deficiencies. The estimated 
population frequency of each coagulation abnormality was compared with the 
proportion of the study group with the corresponding abnormality.
RESULTS: The proportion of abnormalities observed in the study group did not 
differ from the estimated population frequency for protein C, protein S, 
antithrombin III, or factor-V Leiden mutation. A lipoprotein (a) level of >30 
mg/dL (>1.07 micro mol/L) was found in 16% of the study group.
CONCLUSIONS: Our data do not suggest that thrombotic diatheses due to deficiency 
of protein C, protein S, or antithrombin III or due to factor-V Leiden mutation 
are major causes of Legg-Perthes disease. The elevated levels of lipoprotein (a) 
in children with Legg-Perthes disease suggest that they may be at risk for 
atherosclerosis as adults.