Facioscapulohumeral dystrophy (FSHD) is an autosomal-dominant muscular disorder 
associated with a short (<35 kb) EcoRI/BlnI fragment resulting from deletion of 
an integral number of units of a 3.3-kb repeat located at 4q35. In this study, 
we determined fragment sizes separated by pulsed-field gel electrophoresis in a 
patient with an apparently sporadic case of FSHD and in his healthy family 
members. A 38-kb fragment was detected in the proband, in his older brother, and 
in their father. This finding prompted a clinical reevaluation of the father and 
brother. A subclinical phenotype restricted to abdominal muscle weakness was 
detected, and serum creatine kinase values were found to be elevated in both. 
The proband's brother also showed evidence of an independently occurring 
subtelomeric rearrangement of 4q35, which normally occurs in about 20% of the 
population. The identification of a "borderline" 38-kb EcoRI/BlnI fragment in an 
affected subject and his very mildly affected relatives extends the size range 
of disease alleles and expands existing data on the variable intrafamilial 
expressivity of FSHD. This study highlights the importance of a careful 
molecular and clinical analysis extended to family members of apparently 
sporadic cases with larger EcoRI/BlnI fragments for accurate diagnosis and 
appropriate genetic counseling in FSHD.