Myotonic Muscular Dystrophy (MMD)


The major focus in MMD research has been on the molecular underpinnings of the disease. To date, most of the work has been done using animal and cellular models of type 1 MMD. However, many experts believe the findings from the MMD1 experiments will have implications for MMD2 as well.

Medical Management

As yet, there’s no specific treatment that “gets at the root” of type 1 or type 2 myotonic muscular dystrophy (MMD1 or MMD2). Treatment is aimed at managing symptoms and minimizing disability.

This section first addresses medical management of the many symptoms of adult-onset MMD1/MMD2 and juvenile-onset MMD1. Not everyone will require all these aspects of medical management, and some symptoms may first appear or worsen as a person grows older.


What causes MMD?

Type 1 myotonic dystrophy (MMD1) and type 2 myotonic dystrophy (MMD2) dystrophy are both caused by abnormally expanded stretches of DNA. The expansions occur in two different genes but appear to have similar effects on various cells, particularly the cells of the voluntary and involuntary muscles, including the heart and some nerve cells.


Doctors with experience in neuromuscular disorders often find it easy to diagnose type 1 myotonic muscular dystrophy (MMD1). Sometimes, just by looking at a person, asking a few questions and examining him or her, they're well on the way to suspecting MMD1. For instance, teenagers and adults with MMD1 (the most common type) usually have a characteristic long face with hollow temples, and males often have early balding. (See Signs and Symptoms.)

Signs and Symptoms

Myotonic dystrophy is more than just a muscle disease. Both MMD1 and MMD2 affect several aspects of physical and mental functioning, to varying degrees and with variable scope.

The following sections discuss different problems that can occur, although many people with the disease have only some of them. Most of these symptoms can be lessened with treatment. See Medical Management for information on current therapies.

Types of Myotonic MD

The two major types of myotonic muscular dystrophy (MMD) — MMD1 and MMD2 — are both caused by genetic defects.

MMD1, the most common type, results from an abnormal DNA expansion in the DMPK gene on chromosome 19.

MMD2 arises from an abnormal expansion of DNA in the ZNF9 gene on chromosome 3.

Within MMD1 there are additional subtypes, depending on a person’s age at onset of symptoms. The age of onset is roughly correlated with the size of the DNA expansion, with larger expansions associated with earlier disease onset.


What is myotonic muscular dystrophy (MMD)?

Illustration of muscles affected by MMD (front) Illustration of muscles affected by MMD (back)

Myotonic Muscular Dystrophy


MDA leads the search for treatments and therapies for myotonic muscular dystrophy (MMD). The Association also provides comprehensive supports and expert clinical care for those living with MMD.

In this section, you’ll find up-to-date information about myotonic muscular dystrophy, as well as many helpful resources. This information has been compiled with input from researchers, physicians and people affected by the disease.

Research Briefs: FA, MG, MM, MMD1, gene therapy

Edison drugs target FA, mitochondrial diseases