DUCHENNE MUSCULAR-DYSTROPHY AND MYOTONIC-DYSTROPHY IN THE SAME PATIENT

We report on the first patient identified with myotonic dystrophy and Duchenne muscular dystrophy (DMD). The family of the propositus had a strong history of myotonic dystrophy, and there was an intrafamilial p athological expansion of the responsible CTG repeat between the mildly affected mother (160 repeats; normal 27 repeats) and her more severel y affected son (650 repeats), and his sister (650 repeats). The propos itus was an isolated case of Duchenne muscular dystrophy with marked d ystrophin deficiency in muscle biopsy The patient was still ambulatory post age 16. Myotonic dystrophy could interfere to some extent with t he progression of Duchenne dystrophy. However, other interpretations a re possible. Twelve percent of dystrophin revertant fibers as observed by immunohistochemistry could be sufficient to ameliorate typical DMD clinical severity, or the patient may present a somatic mosaic. The p athophysiological interactions of these two unlinked disorders are dis cussed at the clinical and histopathological levels. (C) 1995 Wiley-Li ss, Inc.