*Develops secondarily to many types of disease (''e.g.'' [[Parasitic skin infections - Pathology|ectoparasites]], [[:Category:Integumentary System - Mycotic Infections|fungal infections]], [[Endocrine effects on the skin - Pathology|endocrine disease]], internal disease or allergy)
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*Develops secondarily to many types of disease (''e.g.'' [[:Category:Integumentary System - Parasitic Infections|ectoparasites]], [[:Category:Integumentary System - Mycotic Infections|fungal infections]], [[Endocrine effects on the skin - Pathology|endocrine disease]], internal disease or allergy)
*Microscopically:
*Microscopically:
**Hyperkeratosis and/or parakeratosis of follicles and epidermis
**Hyperkeratosis and/or parakeratosis of follicles and epidermis