Spontaneous skin lesions in beige rats (Chediak-Higashi syndrome of rats).

Beige rats, a model animal of Chediak-Higashi syndrome (CHS), frequently developed the skin lesions consisting of crust formations and alopecia in the skin around the neck from about 4 months of age. Erosion and ulceration were also observed in advance of the skin lesions. In severe cases, the lesions spread to all of the dorsum of the trunk. Skin tissues with or without lesions were studied histopathologically in 41 beige rats comparing with normal skin from 26 age-matched DA rats. Microscopically, epidermal lesions consisted of spongiosis, pustules and erosions with crust. Inflammatory cells in pustules consisted predominantly of eosinophil, and colonization of gram-positive cocci was occasionally observed in the surface area. Mites on the epidermis were also seen in some cases. Dermal lesions were superficial perivascular inflammatory cell infiltrations of eosinophils, neutrophils and mastocytes, and edema under the epidermal lesions. Follicles in the alopecic area showed resting stage and atrophic hair germ, but inflammatory changes were slight. Morphologic characters were very similar to those of chronic eosinophilic dermatitis or spongiotic dermatitis.