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any of various skin diseases characterized by the formation of fine, branny scales.
acute lichenoid pityriasis an acute or subacute, sometimes relapsing, widespread macular, papular, or vesicular eruption that tends to crusting, necrosis, and hemorrhage; when it heals it leaves pigmented depressed scars, followed by a new crop of lesions. Progression to the chronic lichenoid form occasionally occurs.
pityriasis al´ba a chronic condition with patchy scaling and hypopigmentation of the skin of the face.
chronic lichenoid pityriasis a chronic brown to red-brown scaly macular eruption, seen mainly on the trunk, with epidermal changes and a perivascular lymphocytic infiltrate. It may arise independently or happen as a progression of the acute lichenoid form.
pityriasis ro´sea a common acute or subacute, self-limited exanthematous disease of unknown etiology. It begins with a solitary red to tan plaque (herald plaque), usually on the trunk, arms, or thighs, which is followed by similar but smaller papular or macular lesions; these later may peel and leave a scaly collarette.
pityriasis ru´bra pila´ris a chronic inflammatory skin disease marked by pink scaling macules and cone-shaped horny follicular papules; it usually begins with severe seborrhea of the scalp and face, associated with keratoderma of palms and soles.
pityriasis versi´color tinea versicolor.
patchy hypopigmentation of the skin resulting from mild dermatitis.
pi·ty·ri·a·sis al·ba(pit'i-rī'ă-sis al'bă)
Patchy hypopigmentation of the skin resulting from mild dermatitis.