PTCH2 and alopecia: By contrast, PTCH2−/− mutants were viable, fertile and apparently normal; however, alopecia, epidermal hyperplasia, dermal hyperplasia, hair follicle loss, and ulceration were frequently observed with progressing age in PTCH2−/− mutant male mice, whereas PTCH2−/− mutant female mice did not show any abnormalities.