LGMD manual

Dozens of different genes, when mutated, have been shown to cause specific LGMD1 and
LGMD2 subtypes. In these cases, the proteins associated with these genes are nonfunctional or
deficient, and muscles are unable to function normally. Gradually, the muscles become weak
enough that people experience the symptoms of LGMD.
In addition to the known LGMD1 and LGMD2 subtypes linked to specific genes, there are many
cases of LGMD for which the causative gene is not yet known (and people with these cases are
not identified as having a subtype-specific form of LGMD). Scientists are actively working to
understand the causes of these unidentified subtypes of LGMD, because the more we
understand about all the different causes of LGMD and the diverse ways that muscle can be
compromised, the better chance we have of finding effective therapies to intervene in the
pathological process.
1.5. Inheritance pattern
Limb-girdle muscular dystrophy can have different inheritance patterns. Medline Plus 2 states:
Most forms of this condition are inherited in an autosomal recessive pattern, which means both
copies of the gene in each cell have mutations. The parents of an individual with an autosomal
recessive condition each carry one copy of the mutated gene, but they typically do not show
signs and symptoms of the condition.
Figure 2: Autosomal recessive pattern 2
Several rare forms of limb-girdle muscular dystrophy are inherited in an autosomal dominant pattern,
which means one copy of the altered gene in each cell is sufficient to cause the disorder.
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