Want to learn about the symptoms and the cause of Limb Girdle Muscular Dystrophy type 2D (LDMD2D). You’ve come to the right place!
What are muscular dystrophies?
Muscular dystrophies are muscle diseases characterized by muscle weakness and the irreversible wasting away of muscle tissue. These diseases are inherited genetically, which means that it is something you are born with rather than something contagious you acquire from other people like the flu. Although some symptoms of muscular dystrophies are similar to those seen in Multiple Sclerosis (MS), muscular dystrophies are caused by problems in the muscle cells themselves while the symptoms of MS are caused by damage to the central nervous system.
The most common type of muscular dystrophy is Duchenne Muscular Dystrophy (DMD). Symptoms of DMD begin early in childhood and it almost always affects males because it is a recessive disease caused by mutations in a gene on the X chromosome. However, there are many other types of muscular dystrophy and some forms affect both genders equally and cause symptoms that don’t appear until much later in life.
What are LGMDs?
The Limb-Girdle Muscular Dystrophies (LGMDs) are a group of muscular dystrophies that generally first present with weakness in the muscles around the hips and shoulders. Although the subtypes are caused by mutations in completely different genes, they were all called limb-girdle muscular dystrophies because they cause similar symptoms and were first described long before the DNA sequencing technology necessary to identify the cause of each disease was invented. Although muscle weakness is found in every subtype, there are many differences between the diseases including the age of onset, inheritance patterns, and disease severity.
Because the different types of limb-girdle muscular dystrophy are all caused by different genes, a genetic test is required. It is very important to diagnose patients genetically because patient care can differ dramatically between the diseases. For example, although steroids can help patients with some muscular dystrophies, they are harmful to patients with other subtypes. Furthermore, patients cannot participate in many clinical studies or trials without a complete diagnosis.
The limb-girdle muscular dystrophies are separated into 2 main categories based on the inheritance pattern where 1 designates a dominant disease and 2 is a recessive disease (see Genetics for more information). The letters at the end of the disease name were assigned in alphabetic order as the genetic basis for each disease was discovered. Thus, LGMD2D was the fourth recessive limb-girdle muscular dystrophy to be characterized.
What is LGMD2D?
Limb-Girdle Muscular Dystrophy type 2D is caused by mutations in the alpha-sarcoglyan gene that lead to a deficiency of functional alpha-sarcoglycan protein. The precise function of the alpha-sarcoglycan (also called adhalin) is unknown but it is known to interact with the dystrophin, which is the protein that is missing or defective in Duchenne muscular dystrophy.
LGMD2D causes weakness of muscles in the hip, shoulder, and abdomen. Symptoms of LGMD2D often appear before age 10 but in some cases, they do not appear until adulthood. The severity of the disease varies greatly between individuals; in some cases, the symptoms are mild with no effects on lifespan but in extreme cases, the disease can be fatal by the early 20s. In about 20% of patients with LGMD2D, the heart muscles are affected in addition to the muscles of the hip, shoulder, and abdomen. LGMD2D has no effect on intelligence or mental function at any age.
Other names for LGMD2 include Primary Adhalinopathy, DMDA2, Duchenne-Like Autosomal Recessive Muscular Dystrophy, Type 2 and Alpha-Sarcoglycanopathy.
How common is LGMD2D?
LGMD2D is a rare disease and although the exact incidence of LGMD2D is unknown, it is the most common sarcoglycanopathy.