Clinical History
This 5 year old Rhodesian Ridgeback dog had a 2 year history of persistently elevated serum creatine kinase (CK, range 1726 to 7436 IU/L; reference 10-200) and alanine aminotransferase (ALT; range 280 to 436 IU/L; reference 5-107) activities. During this time the dog was asymptomatic. The initial biochemical analysis was performed as a general health screen with periodic rechecks because of the enzyme elevations.

Physical Examination
In June 2009 Bella was presented for exercise intolerance. The dog could play with brief spurts but couldn’t finish walks. The appetite was intermittently decreased. As the serum CK activity remained elevated, a myopathy was suspected and muscle biopsies performed

Diagnostic Testing
Muscle biopsies -  Biopsies were  collected under general anesthesia  from  the triceps brachii and biceps femoris muscles.  Multifocal areas of mixed mononuclear cell infiltrations were observed (Fig. 1) with regional endomysial fibrosis. No organisms were detected.

Antibody titers for infectious diseases –
Neospora IFA - >3200
Toxoplasma IgM  IFA - Negative
Lyme Quantitative C6 Antibody test by ELISA <10
Ehrlichia canis antibody by IFA – Negative
Anaplasma phagocytophilium (previously called Ehrlichia equi) - Negative

Figure 1. H&E stained section from the biceps femoris muscle showing an area of mixed mononuclear cell infiltration (Magnification X 400).

Diagnosis and Outcome
Bella was placed on an 8 week course of Clindamycin (600 mg BID, 83 lb dog). On recheck examination after completion of the antibiotic, exercise intolerance was improved and the dog was reported as 100% back to normal. For the first time the serum CK and ALT activities were within the normal range.