Naturally occurring utrophin correlates with disease severity in Duchenne muscular dystrophy.

Although there is good experimental data that utrophin, the autosomal analog of dystrophin, can ameliorate the phenotype in dystrophinopathies, there is scant evidence from human data to support this hypothesis. We investigated in diagnostic muscle biopsies from 16 patients with Duchenne muscular dystrophy (DMD) the level of utrophin expression using quantitative immunoblot analysis. In 13 of 16 patients, in whom there was adequate follow-up data, utrophin expression was correlated to two clinical endpoints: age at reaching Hammersmith score of 30/40 and age at becoming wheelchair-bound. We found that utrophin expression increases with age in DMD and that there is a significant positive correlation between the quantity of utrophin at initial biopsy and time to becoming wheelchair-bound.