What is Dysferlinopathy?
Dysferlinopathy represents a spectrum of disorders that cause muscle weakness as a result of a deficiency of the protein, dysferlin. Symptoms of the disease vary greatly from person to person, even among people in the same family. Some people with the disease can have a mild course, while others may have severe symptoms that can be fatal. Common presentations of this condition are described below.
Limb-Girdle Muscular Dystrophy Type 2B
People with limb-girdle muscular dystrophy type 2B (LGMD2B) develop symptoms at variable ages. Symptoms can present at as early as 14 years of age, although onset in adulthood is possible. LGMD2B does not affect intelligence or mental function; the primary symptom is progressive muscle weakness of the hip, shoulder, and abdomen (proximal muscles). The rate at which the muscles weaken can vary greatly, but many experience progressive weakness to a point where a wheelchair becomes necessary.
Many individuals with LGMD2B live well into adulthood with respiratory failure being the most common cause of death. However, a minority of people with LGMD2B experience respiratory complications (~20%) or heart complications (~10%). Involvement of the heart muscles is less common in type 2B than in other forms of limb girdle muscular dystrophy.
Miyoshi Muscular Dystrophy Type 1
Miyoshi muscular dystrophy type 1 (MMD1) is also associated with muscle weakness, but the muscles involved are those away from the center of the body (distal muscles), such as the legs and calves. Progression tends to be slower.
Other presentations include distal myopathy with anterior tibial onset (initially distal muscle weakness that progressives to the proximal muscles) and scapuloperoneal syndrome (distal muscle weakness with weakness in the shoulder muscles). A few case reports of congenital muscular dystrophy (severe presentation with extremely poor prognosis) have also been reported.
How common is Dysferlinopathy?
There are numerous types of limb-girdle muscular dystrophy. LGMD has an estimated prevalence of 1 in 15,000 individuals. LGMD2B is thought to account for ~5% of all cases of LGMD, though this varies by region. For example, in Japan, LGMD2B accounts for ~19% of all cases of LGMD and 75% of all cases of Miyoshi muscular dystrophy. In addition, LGMD2B is most commonly found in individuals of Libyan and Caucasus Jewish descent.
How is Dysferlinopathy treated?
There is no cure for dysferlinopathy and few effective treatments. Physical therapy is often recommended to retain muscle strength and mobility for as long as possible. Stretching, mechanical aids, or surgery may aid in that goal. As muscles deteriorate, a ventilator may be required to aid breathing. Those who develop heart problems should consult with a cardiologist for symptomatic treatments.
What is the prognosis for a person with Dysferlinopathy?
The outlook for a person with dysferlinopathy varies. Generally, the earlier symptoms begin, the faster they progress. Some people with the disease experience only mild symptoms, and may have near-normal strength. Others with a mild course may remain able to walk for 30 years or more after symptoms appear. People with more severe disease typically become wheelchair-bound approximately 20 years after their diagnosis.