Myotonia in a chow chow

Congenital myotonia was diagnosed in an inbred Chow Chow pup with severe muscle stiffness that regressed with exercise. Voluntary movement, percussion, or needle insertion caused sustained contraction of the muscles involved. Electromyographic recordings from several muscles contained myotonic discharges. Creatine kinase activity was mildly increased. Slight myofiber hypertrophy and a few atrophic fibers were seen in muscle biopsy specimens. Treatment of the pup with procainamide caused a marked decrease in clinical signs. Myotonia congenita in the Chow Chow appears to be inherited as an autosomal recessive trait. This condition can be diagnosed on the basis of clinical signs. Satisfactory clinical management of myotonia congenita can be achieved with procainamide.     

Pemphigus erythematosus in a chow chow

A 3.5-year-old, spayed female, chow chow presented with a pruritic, ulcerative, butterfly lesion on the nasal planum, typical of the pemphigus complex. Pemphigus erythematosus was diagnosed by histopathologic examination. Treatment consisted of enrofloxacin and immunosuppressive therapy with prednisone and azathioprine. Within 5 wk of treatment, the lesions had resolved almost completely.     

Suspected familial renal disease in chow chows

Renal disease was diagnosed in 6 young Chow Chows. Clinical abnormalities included vomiting, polyuria, polydipsia, and weight loss. Common abnormal laboratory findings were azotemia, hyperphosphatemia, hypocalcemia, nonregenerative anemia, and low urine specific gravity. All 6 dogs had similar microscopic renal lesions. characterized by interstitial fibrosis, a population of small glomeruli, and lack of inflammatory cells. A familial basis for the renal disease is suggested because of its development in 4 closely related dogs.     

Familial cataracts and concurrent ocular anomalies in chow chows.

A closely inbred line of Chow Chows affected with congenital cataracts was studied. Sixteen dogs were examined including 1 adult male, 2 adult females, and 13 pups. Twelve of the pups were from 6 different litters, out of 6 different bitches, all sired by 1 adult male. The exact relationship of the thirteenth pup was undetermined. Clinical evaluation included slit-lamp biomicroscopy, biomicroscopic photography, and indirect ophthalmoscopy. Clinical appearance of the cataracts was variable, ranging from incipient nuclear or capsular lesions to advanced cortical opacity. The lens nucleus was most consistently affected, with variable involvement of the lens cortex. Concurrent ocular anomalies of some eyes included wandering nystagmus, entropion, microphthalmia, persistent pupillary membrane remnants, and multifocal retinal folds. A correlation was not apparent between the character or severity of the cataracts and the finding of the other anomalies. Histologic examination of 12 lenses revealed posterior displacement of the lens nucleus, retained lens epithelial cell nuclei in the nuclear and cortical lens, anterior capsular irregularity and duplication, anterior lens epithelial duplication, and posterior subcapsular migration of epithelium. The high incidence of cataract in this family of Chow Chows suggested an inherited defect, although the inheritance pattern was undetermined.