The clinical course and prognosis of Duchenne muscular dystrophy (DMD) was 
compared in patients with deletions of the gene for dystrophin (cDMD) and those 
without such deletions. A total of 24 patients was followed for at least 2 yrs. 
At age 12 the rating of the activities of daily life (ADL) and disease stage 
were less favorable in those patients with deletions of the gene for cDMD. At 
age 14, no difference in ADL and disease stage was observed between the two 
groups. The percent vital capacity was lower in those patients with the cDMD 
deficit. When the prognosis was evaluated by multivariate analysis of the data 
obtained at age 12, the percent of patients predicted as dying before the age of 
20 was 40% for those without the cDMD deficit but 76% for those who were cDMD 
defective. None of the cDMD defective patients lived longer than 20 yrs, whereas 
5 of 14 patients without the cDND deficit survived longer than 20 yrs. Disorders 
such as cardiac and respiratory failure were also seen more frequently in the 
cDND defective patients. These results suggest that patients with Duchenne 
muscular dystrophy with defective cDMD have more severe disease than those 
without cDMD deficit.