We report on a family with a boy affected by Duchenne muscular dystrop
hy (DMD) and an asymptomatic cousin with a Becker-type dystrophin abno
rmality, diagnosed by chance, Dystrophin gene analysis showed that the
se conditions were caused by two distinct deletions with breakpoints i
n different exons. In Xp21 families, DNA analysis and dystrophin testi
ng of asymptomatic males with high CK plasma levels might detect diffe
rent dystrophin mutations in separate haplotypes as in our family, alt
hough we stress there should be clear clinical or familial indications
for such testing. (C) 1995 Wiley-Liss, Inc.