The first distinction between the two is tne manner of inheritance. Becker's follows the autosomal recessive patter, that is two copies of the gene in each cell are altered. Commonly each parent carries on copy of the altered gene but they do not have any symptoms myself. Thomsen's is autosomal dominant meaning only one copy of the altered gene is necessary to give rise to the condition, usually one parent already suffers from MC.

The second concerns muscles weakness, or ataxia. People with Becker's MC experience attacks of temporary muscle weakness in their arms, hands and legs. This can develop into a permanent weakness.

Myotonic symptoms also seem to be worse in those people with Becker's.

I have Becker's variant MC. My parents and grandparents were all screened for the condition and the pattern of inheritance was confirmed as autosomal recessive. I suffer the muscle weakness, in fact it's quite bad today in my arms, and I have had incidents were my knee joints have just given way without warning. Very embarressing if I happen to be in a bar! My myotonic symptoms are severe and I am prone to temporary paralysis if I trip or get knocked unexpectedly; a fractured skull is the worst injury I've suffered so far as a result of this occurring.

I understand that the general trend is not to make too much of the differences between Thomsen's and Becker's but to me there seems to be a degree of significance that should not be overlooked.

Type of Myotonia: Becker's

Country: England