Equine muscular dystrophy with myotonia.
OBJECTIVE
To describe a case of equine muscular dystrophy with myotonia.


METHODS
A 5-year-old horse presented with hypertrophy and delayed relaxation of the muscles of the hindlimbs from age 2 months. Testicular atrophy developed from 2 years of age. Action and percussion myotonia was associated with weakness in these muscles, and EMG showed diffuse myotonic discharges and myopathic features. Biopsy of the gluteal muscle showed adipose and connective tissue infiltration, marked variation in muscle fibre size, and moth-eaten, ring and whorled fibres.


RESULTS
Injection of apamin, a peptide blocker of calcium-activated potassium channels, which inhibits myotonia in human myotonic dystrophy, was ineffective in blocking myotonic discharges. Discharges promptly abated with 2% lidocaine injection.


CONCLUSIONS
Myotonia in this horse is associated with dystrophic changes similar to human myotonic dystrophy, though there are some pharmacological differences.
Montagna
P
P
Institute of Clinical Neurology, University of Bologna Medical School, Via U. Foscolo 7, 40123, Bologna, Italy. pmontagn@neuro.unibo.it
Liguori
R
R
Monari
L
L
Strong
P N
PN
Riva
R
R
Di Stasi
V
V
Gandini
G
G
Cipone
M
M
D000779:Anesthetics, Local / Q000627:therapeutic use; D000818:Animals; D001030:Apamin / Q000627:therapeutic use; D001284:Atrophy; D004576:Electromyography; D006614:Hindlimb; D006734:Horse Diseases / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D006736:Horses; D006984:Hypertrophy; D008012:Lidocaine / Q000627:therapeutic use; D008297:Male; D009126:Muscle Relaxation; D018908:Muscle Weakness / Q000209:etiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D009137:Muscular Dystrophy, Animal / Q000150:complications* / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D009222:Myotonia / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary*; D009431:Neural Conduction; D013737:Testis / Q000473:pathology; D017211:Treatment Failure
D000779:Anesthetics, Local; D001030:Apamin; D008012:Lidocaine