XII: Diseases of the skin and subcutaneous tissue

L40-L45: Papulosquamous disorders

Papulosquamous disorders encompass a category of skin disorders that are identified by raised bumps (papules) and scaling (squamous). These conditions include psoriasis, lichen planus, and pityriasis rosea among others. Generally, these skin disorders share a typical pattern of inflammation and abnormal skin cell production, which results in reddish lesions that are often itchy and scaly. The exact causes vary for each specific disorder; for example, psoriasis can be influenced by genetic factors and an overactive immune system, while pityriasis rosea is believed to possibly have a viral origin. These conditions can present at different stages of life and affect any part of the body. Unlike some other skin conditions, papulosquamous disorders are not contagious. The progression and severity of these disorders can differ greatly, varying from mild and temporary to severe and persistent conditions.