Overview
Myotonic dystrophy type 3 (DM3) is an extremely rare condition that belongs to the myotonic dystrophy family of diseases. Myotonic dystrophies are inherited muscle disorders where the muscles have trouble relaxing after they contract — a problem called myotonia. The broader myotonic dystrophy group includes the well-known type 1 (DM1) and type 2 (DM2), but DM3 is a proposed or provisional classification that has been described in only a very small number of families or individuals who do not fit neatly into the DM1 or DM2 categories. Because of this, the scientific and medical understanding of DM3 is still very limited and evolving. Like other myotonic dystrophies, DM3 is thought to affect multiple body systems beyond just the muscles. This can include the heart, eyes, and possibly the brain. Symptoms may include muscle stiffness, weakness, and difficulty relaxing the grip after holding something. However, because so few cases have been confirmed and studied, the full picture of how DM3 affects the body is not yet well understood. There is currently no cure for DM3, and treatment is focused on managing symptoms. Care is typically provided by a team of specialists who address muscle, heart, and other system problems as they arise. Research into the myotonic dystrophy family of diseases is ongoing, and advances in understanding DM1 and DM2 may eventually help clarify DM3 as well.
Key symptoms:
Muscle stiffness (myotonia) — difficulty relaxing muscles after useMuscle weakness, especially in the hands, arms, and legsDifficulty releasing grip after holding objectsFatigue and low energyPossible heart rhythm problemsPossible eye changes such as early cataractsPossible difficulty swallowing
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for Myotonic dystrophy type 3.
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Myotonic dystrophy type 3.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How certain are you that I have myotonic dystrophy type 3, and what testing was done to rule out DM1 and DM2?,What genetic testing should I have, and should my family members be tested?,How often should I have my heart monitored, and what symptoms should prompt an emergency visit?,Are there any clinical trials or research studies I could participate in?,What physical therapy or exercise program is safe and helpful for my condition?,Should I be screened for breathing problems during sleep?,Are there patient support groups or specialists who have experience with myotonic dystrophy type 3?
Common questions about Myotonic dystrophy type 3
What is Myotonic dystrophy type 3?
Myotonic dystrophy type 3 (DM3) is an extremely rare condition that belongs to the myotonic dystrophy family of diseases. Myotonic dystrophies are inherited muscle disorders where the muscles have trouble relaxing after they contract — a problem called myotonia. The broader myotonic dystrophy group includes the well-known type 1 (DM1) and type 2 (DM2), but DM3 is a proposed or provisional classification that has been described in only a very small number of families or individuals who do not fit neatly into the DM1 or DM2 categories. Because of this, the scientific and medical understanding of
How is Myotonic dystrophy type 3 inherited?
Myotonic dystrophy type 3 follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Which specialists treat Myotonic dystrophy type 3?
5 specialists and care centers treating Myotonic dystrophy type 3 are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.