What was the alphanumeric classification of limb-girdle muscular dystrophy (LGMD)?

Updated: Aug 15, 2019
  • Author: Monica Saini, MD, MBBS, MRCP(UK); Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

In 1995, an alphanumeric system of LGMD classification was introduced. This assigned a number based on mode of inheritance (1: autosomal dominant; 2: autosomal recessive), and an alphabet based on the order of discovery of linkage to a specific, certain genetic locus or a new disease gene. At the time of this writing, more than 30 genetic subtypes of LGMD have been identified. As the list continued to expand, a lack of consensus on nomenclature was evident, once classification exceeds LGMD 2Z. As of 2017, there are 34 types of LGMD detailed in the OMIM database.

Notably, LGMD subtypes are phenotypically highly variable, limb-girdle weakness may not be the predominant presentation, and mutation in genes assigned to LGMD subtypes may cause allelic conditions with a different phenotype. For example, mutations in TTN gene may present with a wide range of phenotypes ranging from congenital myopathy to late-onset distal myopathy. [2]


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