What are the signs and symptoms of glycosyltransferase deficiency congenital muscular dystrophy (CMD)?

Updated: Jul 03, 2019
  • Author: Emad R Noor, MBChB; Chief Editor: Amy Kao, MD  more...
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Answer

Mutations in 12 genes involved in glycosylation of α-dystroglycan are known to cause congenital muscular dystrophy.

Initially, mutations in different genes were thought to cause separate disorders. However, it has now been clearly demonstrated that mutations in these genes can result in overlapping phenotypes with a wide range of phenotypic variability. Similarly, many of the originally described phenotypes can be caused by more than one gene mutation.

In these congenital muscular dystrophies, the severity of changes in affected tissue has a rank order. This order is possibly related to the degree of preserved α-dystroglycan function.

In the mildest disease, only the skeletal muscle is affected. This is classified by OMIM as type C; limb-girdle phenotype. Type B represents congenital onset with or without mental retardation.

As severity progresses, the cerebellum and then the pons, eyes, and cerebrum are affected. This most severe form is classified by OMIM as type A; congenital with brain and eye abnormalities.

An order of worsening severity in each affected tissue is also observed.

  • In mild disease, patients may have normal muscle and only mild eye and cerebellar abnormalities.

  • In intermediate disease, patients may have mild dystrophic changes, myopia, pontocerebellar hypoplasia, and focal pachygyria.

  • In severe disease, patients may have active muscle fiber degeneration and necrosis, nonfunctioning eyes, severe pontocerebellar hypoplasia, and agyria.


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