Technical standards and guidelines for myotonic dystrophy type 1 testing.

Myotonic dystrophy type 1 is an autosomal dominant multisystem condition. Myotonic dystrophy type 1 is the result of an unstable CTG expansion in the 3'-untranslated region of the myotonic dystrophy protein kinase gene. The age of onset and the severity of the phenotype are roughly correlated with the size of the CTG expansion. The combination of Southern transfer and polymerase chain reaction provides an accurate means of identifying patients affected by myotonic dystrophy type 1. This document follows the outline format of the general Standards and Guidelines for Clinical Genetics Laboratories. It is designed to be a checklist for genetic testing professionals who are already familiar with the disease and the methods of analysis.