Types of Myotonic Dystrophy (DM)

1. DM1 (Myotonic Dystrophy Type 1)

DM1 is a genetic disorder characterized by progressive muscle wasting and weakness. It is an autosomal dominant condition caused by an expanded CTG trinucleotide repeat in the DMPK gene. Individuals with DM1 may experience myotonia (prolonged muscle contraction), weakness in facial and distal muscles, cardiac issues, and intellectual impairment.

2. DM2 (Myotonic Dystrophy Type 2)

Similar to DM1, DM2 is an autosomal dominant disorder with symptoms such as muscle weakness and myotonia. However, it is caused by an expanded CCTG repeat in the CNBP gene. DM2 typically has a later onset and milder symptoms compared to DM1.

3. DMx (Myotonic Dystrophy, not yet classified)

DMx is a term used when myotonic dystrophy symptoms are observed, but the genetic cause has not been identified or classified. Further genetic testing and research may be necessary to determine the specific subtype.

4. DM-like (Myotonia Congenita, Thomsen Disease)

Myotonia Congenita is characterized by muscle stiffness and difficulty relaxing muscles after contraction. Thomsen Disease, an autosomal dominant form, usually manifests in childhood with myotonia but generally without significant muscle weakness.

5. DMPK (Dystrophia Myotonica Protein Kinase)

DMPK is a gene associated with both DM1 and DM2. Mutations in this gene result in the production of abnormal RNA, contributing to the development of myotonic dystrophy.