Distal Muscular Dystrophy Fast Facts

Distal muscular dystrophy (DD) is a genetic disorder that usually begins in adulthood.

Muscular dystrophy refers to a group of diseases affecting the body’s muscles. DD primarily causes muscle weakness and deterioration in the lower legs and arms, but it can also affect other parts of the body.

Some forms of muscular dystrophy can cause intellectual disabilities, but DD is less likely to affect the brain.

People with some types of DD may develop heart problems or respiratory infections that can be life-threatening.

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Some forms of muscular dystrophy can cause intellectual disabilities, but DD is less likely to affect the brain.

What is Distal Muscular Dystrophy?

Distal muscular dystrophy (DD) is a group of inherited diseases that cause muscle weakness and deterioration. DD primarily affects the muscle of the extremities (distal muscles), and the lower legs and arms are the most common sites for symptoms.

The genetic mutations that cause DD are present at birth, but the disease symptoms usually don’t emerge until adulthood. DD is also sometimes called distal myopathy.

Muscular dystrophy (MD) is a collective term that refers to a collection of more than 30 diseases. The common characteristic of all the diseases is that they cause muscle weakness and a progressive loss of muscle tissue. Unfortunately, there is no known cure for these diseases, including DD.

Symptoms of Distal Muscular Dystrophy

Symptoms of DD usually appear first in adulthood and get progressively worse. Symptoms vary in severity from case to case, and not all people with DD will have the same symptoms.

Symptoms of DD can include:

  • Muscle weakness and loss of muscle mass
  • Weakness in the feet or legs that causes walking difficulties
  • Weakness in the hands that affects grip strength
  • Difficulty speaking
  • Problems with swallowing

Types of Distal Muscular Dystrophy

DD can be categorized into several different types depending on the gene mutation that causes the disease. Types of DD include:

  • Welander distal myopathy is a slow-progressing type that usually emerges after age 40 and causes weakness in the hands, feet, fingers, and toes. The heart may also be affected.
  • Udd distal myopathy generally affects the ankles and shins, and muscle deterioration may eventually spread to the upper legs.
  • Miyoshi myopathy often emerges in adolescence or early adulthood with weakness that begins in the calves.
  • Hereditary inclusion-body myopathy type 2 typically affects the feet and thighs.
  • Nonaka distal myopathy typically affects the shins before spreading to the upper legs, arms, and neck.
  • Distal myopathy with vocal cord and pharyngeal signs is a rare type that affects the hands, feet, throat, and vocal cords.

What Causes Distal Muscular Dystrophy?

Muscular dystrophy occurs when the body cannot produce the proteins needed to build and protect muscle cells. Genes control the production of these proteins, and each type of MD is characterized by a gene abnormality that causes the abnormal production of a particular protein.

In the case of DD, an abnormal change (mutation) in one of several different genes interferes with the production of key proteins needed for the development and health of muscle cells. The lack of proteins causes muscle cells to be especially susceptible to damage and death.

Is Distal Muscular Dystrophy Hereditary?

All forms of DD are inherited disorders. Most types of DD are inherited in an autosomal dominant pattern, meaning that children may develop the disorder if they inherit even one copy of the mutated gene from either of their parents. If a parent carries the disorder-causing mutation, they will have a 50 percent chance of having an affected child with each pregnancy.

Some types of DD, including Myoshi distal myopathy and Nonaka distal myopathy, are inherited in an autosomal recessive pattern. This means a child must inherit two copies of the gene mutation, one from each parent, to develop the disorder. People with only one copy of the mutated gene will not develop DD but will be carriers who can pass the mutation on to their children. Two carrier parents have a 25 percent chance of having a child with DD with each pregnancy. Half of their pregnancies will produce a carrier, and a quarter of the pregnancies will produce a child with no mutated genes.

How Is Distal Muscular Dystrophy Detected?

Possible signs of DD include:

  • Difficulty lifting your feet
  • Dragging your feet while walking
  • Difficulty raising your knees to walk
  • Difficulty doing tasks, such as holding a pen or typing, requiring grip strength or finger dexterity

How Is Distal Muscular Dystrophy Diagnosed?

If a doctor is presented with symptoms that look like those of muscular dystrophy, they will begin the diagnostic process by conducting a physical exam and gathering a medical history. If it appears that a muscle disease is likely, several different tests can help determine if there is a muscle problem and which disease is the cause.

Possible diagnostic tests include:

  • Creatine kinase (CK) test. Creatine kinase (CK) is a type of protein called an enzyme. CK in the blood is normal, but higher enzyme levels are created when muscles are damaged. When there is no apparent muscle injury, an elevated CK level can show the presence of a muscle disease like DD.
  • Electromyography. This test uses an electricity-sensing needle probe to measure muscle function. The test can detect muscle abnormalities that could be a sign of DD.
  • Muscle biopsy. This test involves removing and examining a small amount of muscle tissue. A biopsy may be able to detect muscle abnormalities caused by DD.
  • Imaging exams. Imaging exams such as magnetic resonance imaging (MRI) or computerized tomography (CT) may detect the deterioration of muscles.
  • Genetic testing. These blood tests look for the specific genetic abnormalities responsible for different types of DD.


How Is Distal Muscular Dystrophy Treated?

There is no cure for DD, and no treatment will reverse the progression of its symptoms. With treatment, symptoms can sometimes be managed to help prevent severe, life-threatening complications. Possible treatment options include:

  • Physical therapy
  • Mobility aids such as braces or wheelchairs
  • Respiratory therapy or breathing assistance
  • Speech therapy

How Does Distal Muscular Dystrophy Progress?

DD symptoms typically progress slowly after symptoms first emerge, and the progression of symptoms can vary depending on the type of DD and from individual to individual.

Potential complications of DD include:

  • Limited mobility. Muscle weakness can make it hard to get around, and some people with DD eventually lose the ability to walk.
  • Respiratory problems. In rare cases, the muscles responsible for controlling breathing can be affected, making it difficult for people to breathe normally.
  • Swallowing problems. Muscles that control the swallowing reflex can be affected by some types of DD. Swallowing difficulties can also lead to the aspiration of food or liquids into the lungs, leading to potentially fatal respiratory infections.
  • Heart problems. Some types of DD may cause progressive damage to the heart muscle, and this heart damage can result in life-threatening complications.

How Is Distal Muscular Dystrophy Prevented?

There is no known way to prevent DD in someone born with a genetic mutation responsible for the disease. Parents with a family history of the disorder or who have had another child with DD are advised to consult a genetic counselor to assess their risk if they plan to have another child.

Distal Muscular Dystrophy Caregiver Tips

Studies have shown that caring for someone with muscular dystrophy can significantly negatively impact the caregiver’s life. Caregivers are at risk for depression, sleep problems, stress, anxiety, relationship problems, and low self-esteem.

Because of these risks, caregivers must take advantage of support systems to keep themselves healthy. The Muscular Dystrophy Association maintains a collection of resources for caregivers that includes educational resources, guides, and links to caregiver networks and support groups.

Many people with MD also suffer from other brain-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with DD and other forms of MD:

Distal Muscular Dystrophy Brain Science

The most apparent effects of muscular dystrophy occur in the muscles, but it’s not uncommon for MD sufferers to also have cognitive or mental health problems. This suggests that MD can also affect the brain. Researchers are trying to understand how abnormalities in protein production that weaken muscles might harm brain development or function.

  • The genetic mutation that causes myotonic MD produces a toxic chemical that damages muscle tissue. But symptoms of myotonic MD also often include memory, cognitive, and behavioral problems, leading scientists to suspect that the toxic chemical might also damage the brain. Studies have shown that the chemical is present in myotonic MD patients’ brains, and animal studies have shown that the chemical could produce neurological symptoms.
  • People with Duchenne MD (DMD) often suffer from cognitive limitations and psychological disorders such as attention-deficit/hyperactivity disorder (ADHD) or obsessive-compulsive disorder (OCD). Dystrophin, the protein impacted by DMD, is also present in the brain, but scientists are not yet sure what it does there. Even though the protein’s role in the brain is still unknown, one study has linked dystrophin deficit with changes in brain development and a higher risk of cognitive problems.

These research areas could be the first steps in understanding the neurological impact of MD, and a broader understanding could lead to more effective treatments.

Distal Muscular Dystrophy Research

Title: Multi-Center Study of ManNAc for GNE Myopathy (MAGiNE)

Stage: Recruiting

Principal Investigator: Anthony A. Amato, MD

Brigham and Women’s Hospital

Boston, MA

GNE myopathy is a rare genetic muscle disease characterized by progressive muscle atrophy and weakness. The disease is caused by mutations in the gene that encodes the enzyme that initiates and regulates N-acetylneuraminic acid (Neu5Ac) biosynthesis and glycan sialylation. Currently, there is no therapy available for this disease. N-Acetylmannosamine (ManNAc), an orphan drug in development for GNE myopathy, is an uncharged monosaccharide and the first committed precursor in Neu5Ac biosynthesis. In this randomized, double-blind, placebo-controlled trial, the efficacy and long-term safety of ManNAc will be evaluated in subjects with GNE myopathy.

A total of 51 eligible subjects will be randomized in a 2:1 ratio to receive either ManNAc at 4 g three times daily (total of 12 g/day) or a placebo. Subjects will have follow-up visits every 6 months (±7 days) and take the study drug for a minimum of 24 months until their final study visit. The final on-site study visit for a subject is the last expected 6-month follow-up visit before the last randomized subject is expected to reach 24 months (extended follow-up).

Subjects will undergo screening and baseline evaluations that include clinical laboratory tests, Quantitative Muscle Assessment (QMA), the Inclusion Body Functional Myositis Rating Scale (IBMFRS), other patient-reported outcomes (PROs), and rehabilitation medicine functional assessments. Follow-up evaluations will occur every six months following baseline until 24 months after randomization of the last subject. Phone follow-up will occur every month without a clinic visit for the duration of the trial, and the last visit for each subject will be followed by phone follow-up 1 month after the final study visit.


Title: Congenital Muscle Disease Study of Patient and Family Reported Medical Information (CMDPROS)

Stage: Recruiting

Principal Investigator: Gustavo Dziewczapolski, PhD

Congenital Muscle Disease International Registry

Lakewood, CA

The Congenital Muscle Disease Patient and Proxy Reported Outcome Study (CMDPROS) is a longitudinal ten-year study to identify and trend care parameters and adverse events in congenital muscle diseases using the Congenital Muscle Disease International Registry (CMDIR) to acquire necessary data for adverse event calculations (intake survey and medical records curation). To support this study and become a participant, we ask that you register in the CMDIR. You can do this by visiting www.cmdir.org. There is no travel required.

The registry includes affected individuals with congenital muscular dystrophy, congenital myopathy, and congenital myasthenic syndrome and registers through the late onset spectrum for these disease groups. The CMDIR was created to identify the global congenital muscle disease population to raise awareness, standards of care, clinical trials, and in the future, treatment or cure. Simply put, researchers will not be successful in finding a treatment or cure unless they know who the affected individuals are, what the diagnosis is, and how the disease is affecting the individual.

Registering in the CMDIR means participants will enter demographic information and complete an intake survey. They are then asked to provide records regarding the diagnosis and treatment of CMD, including genetic testing, muscle biopsy, pulmonary function testing, sleep studies, clinic visit notes, and hospital discharge summaries.


Title: Clinical Trial Readiness for the Dystroglycanopathies

Stage: Recruiting

Principal Investigator: Katherine Mathews, MD

University of Iowa

Iowa City, IA

Muscular dystrophies are a diverse group of inherited disorders characterized by progressive muscle weakness and wasting. The disorders are caused by mutations, or changes, in genes. Genes are tiny pieces of inherited material (DNA) that direct the body to make certain proteins.

In this study, researchers will examine the clinical presentation of muscular dystrophy caused by abnormal glycosylation of alpha-dystroglycan. Patients with dystroglycanopathies could have mutations in any of the 18 currently identified genes or evidence of dystroglycanopathy in biopsied muscle tissue. Symptoms range from congenital muscular dystrophy that may involve the brain and eye through an adult-onset limb girdle muscular dystrophy.

The study involves a clinical evaluation at the University of Iowa. The assessment includes muscle strength and motor ability testing, lung function testing, quality of life and activity assessment, and a review of past medical history. Portions of this evaluation will be repeated yearly. Financial assistance is available for travel to Iowa City. Support is also available for genetic testing for people with a dystroglycanopathy diagnosis based on muscle or skin biopsy analysis.

Knowledge gained from this study will improve healthcare recommendations for people with dystroglycanopathies and provide a baseline for further study, including potential treatment options.

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