Integrin alpha 9, a new CMD gene is identified

A new gene has been identified that leads to a form of CMD that shares similarities with collagen VI CMD subtype (Ullrich/Bethlem).

What is the gene?

The gene is called integrin alpha 9.  It maps to the following genetic location, 3p23-21.

 

How does an integrin alpha 9 mutation affect people?

  1. Finger, wrist and toe hyperlaxity: this means extremely flexible fingers and wrists that are commonly referred to as “double jointed”
  2. Ankle, knee and shoulder contractures: stiffness in these joints with decreased flexibility
  3. Hyotonia, muscle weakness at birth with contractures
  4. Generalized slowly progressive muscle weakness over time
  5. Intelligence is normal
  6. CPK (creatine phosphokinase) levels are normal to mildly elevated (17-959 U/l)
  7. Lung capacity is diminished on average by 50%, but seemingly stable over long periods of time. Most people do not develop respiratory failure in spite of diminished lung capacity.
  8. All cases described were able to walk many through adulthood. Some people with integrin alpha 9 mutations lost this ability and became wheelchair dependent.
  9. Scoliosis, no rigid spine

Some of these features are similar to findings in the collagen VI CMD subtype. Distinguishing features from the collagen VI subtype include the absence of:

  • a high arched palate
  • torticollis (stiff neck)
  • skin textural changes
  • prominent calcaneus (heel bone)

This form of CMD was first described by Dr. Tetreault and Dr. Brais in a medical article entitled “A new form of CMD with joint hyperlaxity maps to 3p23-21”, published in Brain, 2006.  This form of CMD is described in the French Canadian population.  Given the results of genetic linkage analysis, there is a likely founder mutation in the French Canadian population which accounts for the frequency of this disease within a regional area of the Province of Quebec, Canada.  In all cases, collagen VI genes were tested and no genetic mutation was found.

 

Tetreault M, Duquette A, Brais B, et al. A new form of congenital muscular dystrophy with joint hyperlaxity maps to 3p23-21. Brain Aug 2006; 129(Pt8):2077-84.

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  • Congenital Muscular Dystrophy

    A group of diseases causing muscle weakness at birth. Several defined genetic mutations cause muscles to break down faster than they can repair or grow. A child with CMD may have various neurological or physical impairments. Some children never gain the ability to walk, while others lose the ability as they grow older. Learn more...

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