Direct Diagnosis of Myotonic Dystrophy with a Disease-Specific DNA Marker

Abstract
Myotonic dystrophy is the most common inherited form of muscular dystrophy affecting adults. Its symptoms are not confined to muscle, and variability in their nature and in the patient's age at their onset can make diagnosis difficult. A specific unstable DNA sequence associated with myotonic dystrophy has recently been identified. We describe the use of a DNA probe (p5B1.4) that can detect this mutation directly, improving the accuracy and speed of diagnosis.