Clinical History
A 9-month old male neutered domestic short haired cat was presented to the internal medicine service at Davies Veterinary Specialists, Higham Gobion, UK, for investigations of regurgitation, poor weight gain and an unusual gait.  The cat was reported to have experienced episodes of regurgitation since it was started on solid food with the frequency of these episodes recently increasing.  The cat had no other medical history, exposure to toxins or trauma.  Routine vaccinations were up-to-date and the cat was not on any treatment at the time of referral.  The littermates and parents were apparently unaffected.

Physical and Neurological Examination
The cat weighed 2.3 kg; physical examination confirmed a poor body condition (body condition score 2/5 normal 3/5) with mild atrophy of temporalis, paraspinal and distal limb muscles.  Neurological findings included a stiff gait with increased muscle tone and decreased withdrawal reflexes on all four limbs and absent gag reflex.  A generalized myopathic disorder was suspected, with an inflammatory, infectious, dystrophic or other congenital myopathy as the primary differential diagnoses. 

Diagnostic Testing
The results of complete blood count and serum biochemistry revealed a marked elevation of serum creatine kinase (CK; >40,000 IU/L, reference range <200 IU/L) and an elevated aspartate amino transferase (AST; 566 IU/L, reference range <60 IU/L), suggesting muscle disease.  Serum antibody titer for Toxoplasma gondii was negative and lumbar cerebrospinal fluid (CSF) analysis was normal.  Anti-acetylcholine receptor antibody serum titer was negative.  Electrodiagnostic testing was performed under general inhalation anaesthesia.  Concentric needle electromyography of the major groups of the fore- and hindlimbs, paraspinal, masticatory and laryngeal muscles, revealed fibrillation potentials, positive sharp waves and complex repetitive discharges.  A fluoroscopic evaluation of oesphageal motility following a barium meal revealed oesphageal dysmotility (Go to Video Clip) with food failing to enter the stomach.  

Muscle biopsies were taken from the right triceps (Fig. 1), cranial tibial and gastrocnemius muscle for evaluation, and unfixed and fixed (immersed in 10 per cent buffered formalin) biopsies from each site were submitted under refrigeration to the Comparative Neuromuscular Laboratory, University of California, San Diego, USA, by a courier service.  Degeneration and regeneration were the predominant pathological changes within all three muscles submitted (Fig. 1A). Regenerating fibers were of histochemical type 2C.  A few foci of lymphocytic infiltration were present, however, myonecrosis with macrophage infiltration was most prominent.  Endomysial fibrosis was also multifocally observed.  Immunocytochemical staining for dystrophin was negative (Fig. 1B) while staining for spectrin was present (Fig. 1C) confirming diagnosis of dystrophin-deficient muscular dystrophy. Staining of control muscle is shown in Fig. 1D). Under the same general anesthetic a PEG was placed to ensure nutritional intake was maintained.  During placement of the tube the esophagus was inspected by endoscopy and found to be normal.

Diagnosis and Outcome
A diagnosis of dystrophin deficient muscular dystrophy was made based on the dystrophic phenotype in the muscle biopsy sections and the immunohistochemical demonstration of dystrophin deficiency at the muscle membrane (sarcolemma). The cat tolerated the PEG tube feeding well.  Although it was unable to gain weight, the owner felt the cat was stronger.  Unfortunately, 2 months after examination, there was an acute deterioration.  The owners reported that cat became weak with increased respiratory effort.  At that stage, the owners declined further treatment and elected for euthanasia, which was performed by the referring veterinarian.  The cat was not examined at this time by the contributors, but we speculate that it may have developed inhalation pneumonia. Unfortunately there is no specific treatment available for this debilitating muscle disorder.