Inheritance of Tag I, BstE II, and Nco I restriction fragment length p
olymorphisms (RFLP) in three families from St. Petersburg with familia
l hypercholesterolemia (FH) was studied. In two of these families, pol
ymorphic markers of the low density lipoprotein receptor (LDLR) gene c
osegregated with the disease. This data confirmed FH diagnosis based o
n the analysis of blood plasma lipid levels. Three different RFLP hapl
otypes were associated with the disease, suggesting the presence of at
least three point mutations in the LDLR gene in the population studie
d, i.e., suggesting molecular heterogeneity of FH in the St. Petersbur
g population.