Acta Veterinaria Hungarica 55 (1), pp. 87–95 (2007) DOI: 10.1556/AVet.55.2007.1.9 0236-6290/$ 20.00 © 2007 Akadémiai Kiadó, Budapest MYOTONIC DYSTROPHY IN TWO EUROPEAN GREY WOLVES (CANIS LUPUS) Á. PÁKOZDY 1* , M. LESCHNIK 1 , B. NELL 2 , U. S. KOLM 1 , Z. VIRÁNYI 4 , B. BELÉNYI 4 , M. J. MOLNÁR 3 and T. BILZER 5 1 Clinic for Internal Medicine and Infectious Diseases and 2 Clinic for Small Animal Surgery and Ophthalmology, University of Veterinary Medicine Vienna, Veterinärplatz 1, Vienna, A-1210 Austria; 3 Department of Molecular Neurology, National Institute of Psychiatry and Neurology, Budapest, Hungary; 4 Department of Ethology, Loránd Eötvös University, Budapest, Hungary; 5 Department of Neuropathology, Heinrich Heine University, Düsseldorf, Germany (Received 22 December 2005; accepted 24 May 2006) Two related European Grey wolves (Canis lupus) with the history of mus- cle stiffness beginning at 2 weeks of age were examined in this study. Muscle tone and muscle mass were increased in both animals. Muscle stiffness was wors- ened by stress so that the animals fell into lateral recumbency. Blood chemistry revealed mildly increased serum creatine kinase activity. Abnormal potentials typical of myotonic discharges were recorded by electromyography. Cataract, first-degree atrioventricular (AV) block and inhomogeneous myocardial texture by ultrasound suggested extramuscular involvement. Myopathology demonstrated dystrophic signs in the muscle biopsy specimen. The presumptive diagnosis based on the in vivo findings was myotonic dystrophy. Immunochemistry of the striated muscles revealed focal absence of dystrophin 1 and beta-dystroglycan in both cases. Cardiac and ophthalmologic involvement suggested a disorder very similar to a human form of myotonic dystrophy. This is the first description of myotonic dystrophy in wolves. Key words: Muscle, myotonic dystrophy, wolf, electromyography, histology Myotonia is defined as a prolonged contraction or a delayed relaxation of a muscle during voluntary movement and mechanical or electrical stimulation as well. Abnormal relaxation takes place at the muscle membrane level and causes the characteristic repetitive discharges seen on electromyography. Myotonia can * Corresponding author: Ákos Pákozdy; E-mail: akos.pakozdy@vu-wien.ac.at; Phone: 0043 (1) 25077/5101; Fax: 0043 (1) 25077/5101