Pinnal Parakeratotic Hyperkeratosis Consistent With Zinc-Responsive Dermatosis in 16 French Bulldogs

Zinc-responsive dermatosis, characterised by parakeratotic hyperkeratosis, is most commonly reported in Arctic breeds and, more recently, suspected in Boston terriers.

To describe the clinical and histological features of pinnal parakeratotic hyperkeratosis in French bulldogs, evaluate the response to zinc supplementation, and compare tissue zinc concentrations between affected and unaffected dogs.

Sixteen French bulldogs with histologically confirmed parakeratotic hyperkeratosis were identified retrospectively across the United States. Follow-up information was obtained from medical records and owner email surveys. Tissue zinc concentrations were measured by inductively coupled plasma mass spectrometry in skin biopsy samples from affected and control French bulldogs.

All 16 dogs had bilateral pinnal hyperkeratosis; six also had lesions on the nasal bridge, scrotum or tail. Of 12 dogs that received oral zinc supplementation, eight (67%) improved or achieved complete resolution, including four that responded to zinc supplementation alone. Relapse occurred in four dogs following discontinuation of supplementation, with improvement in three upon reintroduction. Tissue zinc concentrations did not differ significantly between affected and control biopsy samples.

French bulldogs may be predisposed to pinnal parakeratotic hyperkeratosis suggestive of zinc-responsive dermatosis. Zinc methionine supplementation at approximately 2 mg/kg/day was associated with clinical improvement in most cases. Prospective studies are warranted to clarify pathogenesis, compare zinc formulations, and establish diagnostic and therapeutic guidelines.