The adrenocortical dysplasia (acd) mouse mutation arose spontaneously in 1985 in the DW/J inbred strain at The Jackson Laboratory. Mice are runted at birth with a high incidence of polydactyly of the hind feet and tail kinks. The mice have heavily pigmented skin, which is very unusual. Pigmentation of mouse skin is not due to the epidermis but rather anagen stage hair follicles that produce melanin in the bulb that is injected into keratinocytes of the developing hair fiber. When follicles enter the resting phase, telogen, pigment is lost and the skin is pink in color. Since adult mice remain in telogen for long periods of time, shaved mouse skin is usually pink in color. The acd/acd mutant mice have unusually dark skin of the nonhaired regions including the muzzle, pinnae, feet, and tail. Vibrissae are often short and curled while body hair is sparse and abnormal. Hydronephrosis occurs secondary to urethral obstruction.
Microscopically, plucked hairs are abnormal with longitudinal fissures and cuticle changes. Zigzag hairs appear to be absent. Histologic evaluation of skin sections revealed interfollicular epidermal pigmentation in mutant but not control mice. Pigment ladened macrophages were present in the dermis of mutant but not control mice. There was moderate thickening of the mutant epidermis. The adrenal cortex of mutant mice was dramatically altered and very small while the size of the cells in this region were 7.5 times larger than those in control mice.
This mutant mouse has been considered as a potential model for hypoadrenalcorticism in humans and dogs. Nonscarring coat color alopecia in blue-coated Doberman Pinschers and other breeds with blue, fawn, or red coats may have similar pigmentation abnormalities with pigment extrusion into the follicular lumen.
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