LAMA2-CMD, MDC1A and Limb Girdle Dystrophy: What’s the difference?

Limb Girdle Dystrophy, MDC1A and LAMA2-CMD. Why are there three different names to describe the one and same disease?

In the past there was no DNA research and the features that could be seen under the microscope were only described later. Therefore, in the past, MDC1A was often referred to on the basis of the muscle weakness pattern that was characteristic: Limb Girdle dystrophy. There are several Limb Girgle dystrophies: MDC1A is one of them. At that time, it was not clear to patients and doctors which form of Limb Girdle dystrophy the patient was suffering from (which error in the DNA caused the muscle disease). So this could be MDC1A, but also another muscle disease.

Later, the MDC1A muscle disease was given a name that referred to the abnormalities seen in the muscle biopsy when examined under the microscope: merosin-negative congenital muscular dystrophy / muscular dystrophy type 1a (MDC1A or CMD type 1a). This means that no protein is seen when staining for the protein merosin or laminin. This is a protein that normally occurs on the surface of muscle cells and ensures anchoring of those cells in the surrounding connective tissue. The absence of merosin (or laminin) leads to muscle weakness.

LAMA2-related congenital muscular dystrophy
Relatively recently, diagnostics based on genetic research (research into a flaw in the DNA) has increasingly come to the fore in the classification of muscle diseases. This has led to a different, new name for the muscle disease: ‘LAMA2-related congenital muscular dystrophy’ or LAMA2-CMD. This name refers to the error in the LAMA2 gene (laminin gene) as the cause of the muscle disease.

The muscle disease can thus be referred to by different names, depending on which classification system is used. It depends (largely) on the age of the patient which classification system was used at the time of diagnosis. As a rule, the older the patient, the more likely the patient was initially referred to as Limb Girdle dystrophy (instead of MDC1A). However, it is not the case that a Limb Girdle dystrophy is always MDC1A: this must be determined with a muscle biopsy and / or genetic examination.

We hope to have given you some clarification on the background to the naming of the muscle disease. On this website we always use the term ‘LAMA2-CMD’ to avoid any confusion.