LGMD stands for limb-girdle muscular dystrophy, a group of genetic diseases that cause progressive weakness in the muscles around the shoulders and hips. It is the fourth most common type of muscular dystrophy, affecting roughly 1.63 per 100,000 people. Unlike some muscular dystrophies that are linked to a single gene, LGMD encompasses over 30 different subtypes caused by mutations in more than 32 different genes.
Which Muscles Are Affected
The name “limb-girdle” refers to the two rings of muscle and bone that connect your limbs to your trunk: the shoulder girdle (connecting your arms) and the pelvic girdle (connecting your legs). Weakness typically starts in one or both of these areas and gradually spreads. Early signs often include difficulty climbing stairs, rising from a chair, lifting objects overhead, or walking long distances. Over time, the weakness can extend to muscles farther from the trunk, including the forearms and lower legs.
Because LGMD covers so many subtypes, the pattern of weakness varies. Some forms affect the hips and thighs first, making walking difficult early on. Others begin in the shoulders, making it hard to raise your arms. In certain subtypes, the calf muscles weaken early and noticeably, making it difficult to stand on your toes.
How LGMD Is Classified
LGMD subtypes were historically labeled with numbers and letters: LGMD1 for dominant forms and LGMD2 for recessive forms, followed by a letter identifying the specific gene. A revised naming system introduced in 2018 replaced this with a clearer format. Now, each subtype is labeled LGMD followed by “D” for dominant or “R” for recessive, then a number based on the order of discovery, and finally the name of the affected protein.
Most cases are autosomal recessive, meaning a person must inherit a faulty copy of the gene from both parents to develop the disease. Parents who each carry one copy are unaffected. A smaller number of subtypes are autosomal dominant, where inheriting just one faulty copy is enough to cause symptoms.
The most common genetic cause involves mutations in the CAPN3 gene, which produces a protein called calpain-3. This causes LGMD R1, the single most frequently diagnosed subtype. The second most common involves the DYSF gene (LGMD R2), which affects a protein involved in muscle fiber repair. Other well-known subtypes involve the sarcoglycan genes (LGMD R3 through R6) and the FKRP gene (LGMD R9).
How It Progresses
LGMD progression varies enormously by subtype and even between individuals with the same mutation. Dominant forms generally progress more slowly, tend to start later in life, and produce milder symptoms. Recessive forms often appear earlier, progress faster, and cause higher levels of muscle damage.
A key milestone in the disease is loss of the ability to walk independently. A systematic review across subtypes found that the average time from symptom onset to needing a wheelchair was shortest for people with early childhood-onset sarcoglycanopathies (LGMD R3 through R6) and LGMD R9, at roughly 12 years. People with late childhood-onset LGMD R2 had the longest average time, around 21 years. In general, earlier onset tends to mean faster progression. About 60% of people with LGMD in one large survey were still walking independently at the time they were assessed.
Diagnosis
Diagnosing LGMD typically starts with a blood test measuring creatine kinase (CK), an enzyme that leaks out of damaged muscle cells. In most forms of LGMD, CK levels are elevated, sometimes dramatically. Sarcoglycanopathies and dysferlinopathy tend to produce very high CK levels, while dominant forms usually cause more modest elevations.
Elevated CK alone does not confirm LGMD, since many muscle diseases raise this enzyme. The definitive step is genetic testing, which identifies the specific gene mutation responsible. This is important not just for confirming the diagnosis but for determining the subtype, which affects prognosis, the risk of heart and lung complications, and eligibility for clinical trials. Muscle biopsy, once the standard diagnostic tool, is now used less often but can still help when genetic results are unclear.
Heart and Lung Monitoring
Certain LGMD subtypes carry a significant risk of heart problems or breathing difficulties, even before a person notices cardiac or respiratory symptoms. Clinical guidelines recommend that people newly diagnosed with most subtypes, particularly the sarcoglycanopathies (R3 through R6), LGMD R9, and several dominant forms, be referred for a heart evaluation including an electrocardiogram and echocardiogram regardless of symptoms.
Lung function testing is also recommended at diagnosis for most subtypes. People with LGMD R9 are at particularly high risk for respiratory decline and should have periodic pulmonary evaluations throughout their lives. A few subtypes, notably LGMD R2 and R12, carry lower cardiac and pulmonary risk and typically only need evaluation if symptoms develop.
Managing LGMD Day to Day
There is currently no cure for any form of LGMD, so management focuses on maintaining function and quality of life for as long as possible. Physical therapy is central to this. A combination of aerobic exercise, gentle strengthening, and stretching throughout the week helps preserve muscle function and cardiovascular health.
Low to moderate-impact aerobic exercise, such as swimming or stationary cycling, is recommended for at least 30 minutes more than once per week. Strengthening exercises should be done at least twice a week with rest days in between, using light weights or resistance. Heavy lifting and exercises that put excessive strain on lengthening muscles, such as deep squats, should be avoided because they can accelerate muscle damage. Stretching helps maintain flexibility and prevent contractures, the tightening of joints that occurs as muscles weaken and shorten.
Assistive devices like braces, walkers, and wheelchairs become important tools as the disease progresses. Occupational therapy can help adapt daily tasks, and respiratory support devices may be needed for subtypes that affect breathing muscles.
Gene Therapy and Clinical Trials
Several LGMD subtypes are being targeted in active gene therapy trials. The most advanced program involves a therapy called bidridistrogene xeboparvovec (SRP-9003), which delivers a functional copy of the beta-sarcoglycan gene to people with LGMD R4. This multicenter global trial uses a single intravenous dose designed to enable muscle cells to produce the missing protein on their own. Natural history studies are also underway tracking the progression of LGMD R1, R3, R4, and R5 to establish baselines that future therapies can be measured against.
Because LGMD encompasses so many genetically distinct diseases, each subtype essentially requires its own targeted treatment. This makes drug development slower than for conditions caused by a single gene, but also means that advances in one subtype can inform approaches to others using similar technology.