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Papulosquamous Disorders

What Are They, Causes, Symptoms and More

Author: Lily Guo

Editors: Alyssa Haag, Emily Miao, PharmD, Kelsey LaFayette, DNP, RN

Illustrator: Jessica Reynolds, MS

Copyeditor: Sadia Zaman, MBBS, BSc

What are papulosquamous disorders?

Papulosquamous disorders are skin disorders that are defined by characteristic lesions consisting of red or purple papules (i.e., a raised area of skin smaller than one centimeter in diameter) with scaly plaques (i.e., a raised area of skin larger than one centimeter in diameter). Examples of papulosquamous disorders include psoriasis, lichen planus, pityriasis rosea, parapsoriasis (including pityriasis lichenoides), and seborrheic dermatitis. The hallmark of these disorders is the sharply demarcated nature of the papules and plaques. 

What causes papulosquamous disorders?

The causes of papulosquamous disorders can vary. For example, psoriasis is an autoimmune-mediated disorder triggered by infections, stress, and cold, causing skin cells to build up at an abnormal rate. Psoriasis is chronic and cannot be cured, however symptoms can be managed with topical medications and/or systemic therapies. Lichen planus is likewise caused by a dysregulated immune response and may be associated with chronic hepatitis C infection; however, unlike psoriasis, lichen planus can resolve over time. On the other hand, pityriasis rosea is typically triggered by a viral infection. The exact cause of pityriasis lichenoides remains unknown; however, it has been postulated that it may occur as a result of a hypersensitivity to bacteria or viruses. Lastly, the exact cause of seborrheic dermatitis is unknown, but it may be related to the fungus, called Malassezia, that is present in the oil secretion on the skin; or an irregular response of the immune system. 

What are the signs and symptoms of papulosquamous disorders?

The signs and symptoms of papulosquamous disorders vary depending on the specific skin condition. 

Psoriasis presents as erythematous (red) papules or plaques with silver scales typically on the extensor surfaces (e.g., elbows and knees) or the scalp. Scaling on the scalp in psoriasis is non-greasy, which can help differentiate psoriasis from other skin conditions affecting the scalp, such as seborrheic dermatitis. Seborrheic dermatitis also presents with dandruff (i.e., skin flakes) on the scalp or within facial hair (e.g., eyebrows, beard, mustache). In contrast to psoriasis, the flaky white scales of seborrheic dermatitis are associated with patches of greasy or red skin. Additionally, with psoriasis, an individual may experience nail pitting, which is when the nails become yellow and thick and can separate from the nail bed. Both psoriasis and seborrheic dermatitis often present with itching.

Lichen planus presents with pruritic (i.e., itchy), violaceous (i.e., purple), polygonal macules or papules that are shiny in appearance and commonly involve the wrists, elbows, and oral mucosa. Pityriasis rosea typically appears on the trunk as pink-to-red oval papules, alongside a larger, erythematous (i.e., red), scaly plaque, called the herald patch. Lesions associated with pityriasis rosea typically persist between 4-8 weeks. Lastly, pityriasis lichenoides is a rarer condition that resembles pityriasis rosea. It can persist for 2-3 years and mostly affects adults assigned male at birth. 

How are papulosquamous disorders diagnosed and treated?

Diagnosis of papulosquamous disorders relies on a clinical exam by a clinician as well as testing using skin biopsy and histopathology, in some cases. Treatment subsequently depends on the specific underlying condition. Psoriasis may be treated with moderate-to-high potency topical corticosteroids. Corticosteroids may be used in combination with topical calcipotriene (i.e., a vitamin D analog). For treating psoriatic nails, one may use tazarotene, which is a type of retinoid. If there are scales on the scalp, salicylic acid 3% in mineral oil or tar shampoo may be helpful. For very severe cases of psoriasis, systemic agents, such as oral retinoids, methotrexate, and anti–tumor necrosis factor biologic agents, may be recommended. Lichen planus may be treated with topical steroids for 4 to 8 weeks or oral prednisone for 1 to 2 weeks, in severe cases. Phototherapy can be helpful for the itching and may help speed up recovery. Pityriasis rosea and pityriasis lichenoides can both be treated with sun exposure, or phototherapy (i.e., narrow-band ultraviolet B). Pityriasis lichenoides can also be treated with oral erythromycin, an antibiotic, for 1 to 2 months. The main treatment for seborrheic dermatitis include creams, shampoos or ointments that aim to control inflammation. For example, clinicians may prescribe corticosteroids (e.g., hydrocortisone, fluocinolone, clobetasol and desonide) to be applied to the affected area(s). 

What are the most important facts to know about papulosquamous disorders?

Papulosquamous disorders are skin lesions characterized by well-demarcated, red or purple papules and plaques with scales. Examples include psoriasis, lichen planus, pityriasis rosea, pityriasis lichenoides, and seborrheic dermatitis. Causes range from autoimmune to viral etiologies, and treatment may include topical corticosteroids and phototherapy. While most cases of pityriasis lichenoides tend to resolve on their own over time, psoriasis, lichen planus, pityriasis rosea, and seborrheic dermatitis are typically chronic. 

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