LGMD stands for ‘limb-girdle muscular dystrophy’ which is also sometimes known as ‘Erb’s muscular dystrophy’. This is a rare autosomal (meaning caused by a chromosome that occurs in both sexes) class of muscular dystrophy causing the muscles to waste away and thereby causing weakness and various serious health conditions.
In LGMD, the term ‘limb-girdle’ refers to the fact that the hips and shoulders are the areas most greatly affected – also known as the limb-girdle muscles. This of course ultimately results in the limited use of the arms and legs at those points while the biceps/calves etc may remain relatively intact.
The main symptom of LGMD then is weakness in the shoulders and hips. This affects the ability to move the upper arms and legs in relation to the torso, though it might be relatively easy to bend the limbs at the arm and elbow joints (which are controlled by other muscles). As well as muscle weakness in these areas, other symptoms include:
• Myoglobinuria (brown discoloration of the urine caused by myoglobin)
• Elevated Creatine Kinase in the blood serum (normally employed by healthy muscles in the use of energy)
• The appearance of ‘rippling’ muscles
• Myotonia (muscles being slow to relax after contraction)
• Cardiomyopathy (disease of the heart muscle caused by deterioration of the heart muscle itself)
• Pain may occur but usually is not present with LGMD
• Weakness in the tongue (though not usually the face)
The muscle weakness is usually symmetrical and will be slow to progress. There is no neuropathy nor damage to the senses.
As an autosomal condition, LGMD is normally inherited and is equally likely to occur in both males and females. The onset is usually between the ages of 10-30 though it can begin earlier or later. When LGMD occurs in childhood it is more likely to progress quickly and is usually ultimately more disabling.
LGMD acts by preventing the body from correctly utilizing proteins in the area, and different types of proteins can be affected resulting in various different forms of LGMD. The different classifications of LGMD also refer to the specific genes affected. Largely LGMD is divided into two categories – ‘dominant’ (group 1) and ‘recessive’ (group 2) depending on whether it was caused by a dominant or recessive gene.
Some of the symptoms are specific to particular types of LGMD. For instance in LGMD 2A the hip abductors remain relatively intact, whereas in LGMD 2B the individuals normal have average levels of ability until the abrupt onset of the LGMD symptoms.
Treatment, Management and Prognosis
The treatment for LGMD is currently largely supportive and there is no known cure. This then involves the use of physical therapy and exercise in order to strengthen the muscles as much as possible, while supplementation might be further used to help prevent the break down of muscle and to aid in its construction. Calipers (orthotics that clamp around the limbs and torso as a brace) can be used in order to help support the individual in order to aid mobility and to improve quality of life. It is crucial that careful attention be paid to lung and heart health in case they are affected. IVIg can be used in order to improve strength and to prevent fibrosis and inflammation (whereas corticosteroids have a secondary weakening effect). The most dangerous forms of LGMD are those in which respiratory and cardiac involvement are most likely which are: LGMD 1B, 2C-F and 21. In such cases precautions such as vaccines against influenza and pneumonia are advised. All cases of LGMD are progressive and currently there is no way to reliably prevent the deterioration of muscle, however progression is not always linear – meaning it may pause or even regress.
Promising research is being carried out with regards to many different forms of muscular dystrophy. Gene therapy for instance is an area that is particularly promising, with alterations to individuals’ genetic code potentially being used successful in mice to block the production of myostatin – a naturally occurring muscle suppressant that resulted in 60% more muscle mass. The modification of genes to more effectively use protein in the area likewise could help to counteract the effects of the condition, or it may even be possible to identify and repair the damaged genes that caused LGMD in the first place.