Although one cannot rule out the hypothesis that Ki67-labelled cells immature MCs which have just left the bloodstream to infiltrate the dermis and may be related to enhanced migration of MC precursors from the bloodstream as suggested by previous studies[23], the identification of in situ proliferation of resident MCs in the connective outer root sheath of follicles by Sugavara et al.[56] strongly support our hypothesis of in situ proliferation of resident MCs in canine AD. Here, MKI67 is linked to Alzheimer disease.