The masked rat. An X-ray induced mutant with chronic blepharitis, alopecia, and pasteurellosis.

An autosomal recessive mutation had been previously X-ray-induced in the rat and named the masked rat (genotype mk/mk). This study describes the mutant's appearance, histology, and microflora. The rat's eyelids were swollen, often to the point of closure, and its face was partially covered by a brownish crust, giving the mutant a mask-like appearance. The chronic blepharitis was also accompanied by alopecia that appeared as bare patches across the mutant's back. Pasteurella pneumotropica was found in eyelids and on skin from all masked rats. The normal rat demonstrated a resistance to Pasteurella pneumotropica infection, or, conversely, the masked rat appeared to be genetically predisposed to pasteurellosis.