Sarcoglycanopathy with absent expression of all sarcoglycan proteins in a young cat with clinical features of feline hypertrophic muscular dystrophy.

Case summary: A 1-year-old, male castrated domestic shorthair cat presented for chronic mobility decline and muscle stiffness, first noted at 3 months of age, and persistently elevated serum creatine kinase levels (>19,000-53,000 IU/l). Clinical examination revealed macroglossia and selective hypertrophy of cervical and appendicular muscles. Neurologic evaluation indicated a myopathic gait without pain or neurologic deficits. Muscle biopsy was supportive of muscular dystrophy (MD) and immunohistochemistry demonstrated loss of the sarcoglycan complex with complete absence of all tested sarcoglycan proteins, consistent with a diagnosis of sarcoglycan-deficient MD. These findings contrast with prior feline reports that were mostly limited to reduction or absence of beta-sarcoglycan on immunostaining without overt clinical evidence of MD. A follow-up echocardiogram revealed mild to moderate right ventricular changes without indications for treatment. At 2 months after diagnosis, the patient remained clinically static, suggesting a relatively slow progression despite absent sarcoglycan expression. Relevance and novel information: This case represents the first reported feline sarcoglycanopathy characterized by the absence of all tested sarcoglycan subunits on immunohistochemistry and concurrent presentation of classic Duchenne-like MD signs, including macroglossia and muscular hypertrophy. It expands the phenotypic spectrum of muscular dystrophies in cats, underscoring parallels to limb-girdle muscular dystrophies in humans and dogs. Given the cat's static clinical course and diagnostic overlap with dystrophinopathies, this case suggests sarcoglycan-deficient MD in cats may present with a broader spectrum of severity than previously appreciated. The findings support the potential utility of feline sarcoglycanopathies, when phenotypically consistent with forms appreciated in other species, as spontaneous animal models for comparative medical research.