Limb-girdle muscular dystrophy (LIMB-GIRDLE MUSCULAR DYSTROPHY) can be a complicated subject since there are many different types. Not all of the information on this page will be relevant to everybody with the diagnosis.
What is limb-girdle muscular dystrophy?
Muscular dystrophy is the name given to a group of inherited conditions where there is a progressive wasting and weakening of muscle. There are many different types of muscular dystrophy. One of the ways in which the different types of muscular dystrophy are distinguished is by noting the groups of muscle that are involved first. The limb-girdle group of muscular dystrophies is so called because generally they cause weakness in the shoulder and pelvic girdle for example the big muscles around the top (proximal) part of arms and legs (hip, thigh and shoulder muscles). Usually weakness of the legs is noticed before that of the arms and usually the muscle of the face are unaffected.
What are the common features?
Limb Girdle Muscular Dystrophy are rare conditions and they present differently in many people, even within the same family, with regard to age of onset, areas of muscle weakness, heart and respiratory involvement, rate of progression and severity.
The different types of LIMB-GIRDLE MUSCULAR DYSTROPHY may have different features associated with them and some of these are described in the table below. However, the common features to all people in this group will be weakness of the big muscles of the legs and/or arms. This may result in frequent falls, difficulty in running, climbing stairs and rising from the floor. As the condition progresses, people can have problems with walking and may need to use a wheelchair over time.
The involvement of shoulder and arm muscles can lead to difficulty in raising arms over head and in lifting objects. In some types of LIMB-GIRDLE MUSCULAR DYSTROPHY, the heart and breathing muscles may be involved. Consequently regular checks of heart and breathing function may be needed in order to identify any changes and treat them as necessary.
What causes it?
There are many different genetic faults associated with LIMB-GIRDLE MUSCULAR DYSTROPHY and these are listed in the table below. These genes contain the necessary information to make muscles function. When a person has faults in a LIMB-GIRDLE MUSCULAR DYSTROPHY gene, the muscles can not work properly and weakness occurs.
Quite often complex tests may be needed to work out the causes of LIMB-GIRDLE MUSCULAR DYSTROPHY in an individual person, which may include examination of a muscle biopsy and a blood sample for DNA testing.
What are the different types of limb-girdle muscular dystrophy?
The different types of LIMB-GIRDLE MUSCULAR DYSTROPHY have all gone through various name changes and reclassifications over the last few years. They are listed in the table below. All forms of LIMB-GIRDLE MUSCULAR DYSTROPHY have a genetic basis.
The LIMB-GIRDLE MUSCULAR DYSTROPHYs are divided into two main groups depending on the way they are passed on in families. On this basis, they are grouped into autosomal recessive or type 2 LIMB-GIRDLE MUSCULAR DYSTROPHY and the much rarer group of autosomal dominant or type 1 LIMB-GIRDLE MUSCULAR DYSTROPHY. They can now be further subdivided on the basis of the faulty gene or the muscle protein deficiency which may tell us exactly where the problem lies.
What are the genetic implications?
Approximately 90% of LIMB-GIRDLE MUSCULAR DYSTROPHY is inherited as an autosomal recessive disorder. For someone to have one of these conditions they have to have two faulty copies of the gene responsible. All of our genes come in pairs, one from our mother and one from our father.
If some one has an autosomal recessive type of LIMB-GIRDLE MUSCULAR DYSTROPHY both of their parents must be carriers (see diagram). These parents will, together, have a 1 in 4 chance of having another baby with LIMB-GIRDLE MUSCULAR DYSTROPHY.
People with autosomal recessive types of LIMB-GIRDLE MUSCULAR DYSTROPHY rarely have affected children (for the risk of meeting and having a child by a carrier of the same faulty gene will be rare); all of their children will have inherited one copy of the faulty gene but are unaffected.
The remaining subtypes of LIMB-GIRDLE MUSCULAR DYSTROPHY show what is known as autosomal dominant in inheritance. This means that the condition can be passed on from parent to child (of either sex). However, it is important to note that we are increasingly recognising that autosomal dominant conditions can arise as a result of a so-called new fault in the gene (a “new mutation”) meaning that someone can have an autosomal dominant condition without either parent being affected. For the affected person, there is a 50-50 chance that their children could also be affected.
How will it progress?
All Types of LIMB-GIRDLE MUSCULAR DYSTROPHY tend to get worse with time, but this is highly variable from condition to condition and from person to person. It is best to discuss this with your consultant to be sure the information is relevant to your specific case.
For further information/clarification/assistance, please contact: firstname.lastname@example.org