Myotonic dystrophy is an autosomal dominant trinucleotide repeat disorder which causes muscle weakness and myotonia.
It classically presents around the age of 30.
There are 2 main types:
- Dystrophia myotonica type 1
- Commonest – greater than 95% of myotonic dystrophy cases
- On chromosome 19
- More than 50 CTG repeats
- Weakness begins distally
- Dystophia myotonica type 2
- On chromosome 3, CCTG repeats
- Weakness begins proximally
- More benign than dystophia myotonica type 1
Features associated with myotonic dystrophy 1 include
- Frontal balding
- ptosis
- Raised IgG
- Raised CPK
- cataracts
- Daytime hypersomnolence
- Testicular atrophy
- Cardiac conduction abnormalities
- Diabetes mellitus (5%)
There is no cure
References:
