Chronic proliferative dermatitis (cpd) is a spontaneous mutation in C57BL/K
a mice (cpdm/cpdm). The dermatitis is characterized by redness, hairless, s
caling, pruritus and histologically by epithelial hyperproliferation, infil
tration of eosinophils, macrophages and mast cells. Lesions similar to thos
e in the skin occur in the esophagus and forestomach. In this paper, we des
cribe the effect of drug treatments directed against epidermal hyperprolife
ration (calcipotriene and etretinate), against inflammation (corticosteroid
s and dapsone) and against pruritus (loratidine and capsaicin). The criteri
a used to objectively estimate the effect of the treatment were 1) macrosco
pic evaluation of the lesions (cpd score), 2) degree of epithelial hyperpro
liferation assessed by BrdU incorporation and epithelial thickness, and 3)
microscopic evaluation of the inflammatory cells in the skin samples. Treat
ment of the cpdm/cpdm mice with calcipotriene (5 mu g/day for 3 weeks) inhi
bited epidermal proliferation and the number of eosinophils. Systemic etret
inate treatment (30 mu g/g/day for 3 weeks) was not very effective, Topical
corticosteroids (0.05 mu g/day, for 3 weeks) exerted a therapeutic effect
on the hyperproliferation and the number of eosinophils. Oral dapsone treat
ment (34 mu g/g/day, for 5 weeks) reduced the BrdU incorporation in the ski
n and the epithelial thickness in the esophagus, The anti-histamine loratid
ine (orally, 1.7 mu g/g/day, for 3 weeks) reduced the severity of the lesio
ns macroscopically, probably by suppressing the pruritus. Capsaicin (topica
lly, 30 mM, for 5 weeks) also reduced the severity of the macroscopic obser
vable lesions. Moreover, capsaicin reduced the dorsal and ventral epidermal
thickness. The results from this and previous studies indicate that steroi
ds (topically and systemically) and less strongly calcipotriene are the mos
t effective treatments for the lesions observed in the cpdm/cpdm mice, sinc
e both hyperproliferation and the influx of eosinophils are reduced. Althou
gh the pathogenesis of the cpd lesions remains to be determined, our result
s indicate that the cpdm/cpdm mouse can be used to investigate new drugs fo
r their possible application in chronic dermatitis.