Physical Examination
The dog was small for the breed and tired easily on exercise (go to video clip). Diffuse muscle atrophy, an absent gag reflex, and calcified plaques on the tongue were present (Fig. 1,2). The neurological evaluation supported a disorder of the neuromuscular system. A myopathy was suspected.

Figure 1. Diffuse muscle atrophy

Figure 2. Calcific plaques on tongue

Diagnostic Testing

Serum biochemistry – elevated creatine kinase (>30,000 U/L), alanine aminotransferase and aspartate aminotransferase

Electromyography – Generalized spontaneous electrical activity including positive sharp waves, fibrillation potentials, and bizarre high frequency discharges were observed.

Electrocardiography – A sinus arrhythmia with deep Q waves was present. Echocardiography revealed early dilatative changes, with a fractional shortening of 15.2% (normal greater than 25%) indicating decreased cardiac pump function. There were also focal hyperechoic lesions in the interventricular septum. All of these changes were indicative of myopathy

Muscle biopsy and immunofluorescence immunohistochemistry – A biopsy was collected from the cranial tibial muscle. Degenerative and regenerative changes were present within the biopsy specimen with numerous calcific deposits. Fresh frozen muscle sections were incubated with monoclonal antibodies against the rod and carboxy terminus of dystrophin. An antibody against spectrin was used as a control for membrane integrity. Compared to control canine muscle, staining of the sarcolemma was not observed with either dystrophin antibody (Fig. 3.)

Figure 3. Top row = control dog muscle; bottom row = dystrophic dog muscle.

Diagnosis and Prognosis
Muscular dystrophy and cardiomyopathy associated with dystrophin deficiency. This form of muscular dystrophy has been previously reported in the Miniature Schnauzer (Paola et al, 1993). No specific therapies for muscular dystrophy are currently available and the long term prognosis is poor. The dog was supplemented with L-carnitine (500 mg BID), coenzyme Q10 (100 mg total dose SID), and riboflavin (100 mg total dose SID).

Reference
Paola JP, Podell M, Shelton GD (1993). Muscular dystrophy in a Miniature Schnauzer. Prog Vet Neurol 4:14-18.