Facial Discoid Dermatosis: A New Variant of Pityriasis Rubra Pilaris?

Updates on Pityriasis Rubra Pilaris: A Scoping Review

Pityriasis rubra pilaris (PRP) is a rare, inflammatory papulosquamous skin disease with unknown exact etiology. Historically, PRP has been challenging to diagnose, especially during the acute phase, and to treat, due to its unclear pathogenesis. To better inform clinical practice, a literature review was conducted employing a broad search strategy to capture PRP-related published studies between January 1, 2012 to October 31, 2022. Two hundred twenty-one studies were identified, which were categorized into 9 themes: (1) potential causes and triggering factors, (2) comorbidities, (3) diagnostic difficulties, (4) genetics, (5) clinical manifestations and laboratory values, (6) treatment, (7) treatment-related adverse events, (8) quality of life, and (9) other. COVID-19 infection, COVID-19 vaccination, and malignancy were the most commonly reported potential triggering factors. Misdiagnosis is very common during the early acute stages. Pathogenesis and genetic studies have further implicated caspase recruitment domain family member 14 (CARD14) mutations in the development of familial PRP (Type V) and have underlined the overlap between psoriasis and PRP. To date, there are currently no specific and validated scoring systems or tools to assess the severity of PRP. While large, randomized trials are still lacking, biologic agents remain the most effective therapy.

Pityriasis Rubra Pilaris: An Updated Review of Clinical Presentation, Etiopathogenesis, and Treatment Options

Pityriasis rubra pilaris (PRP) is a rare papulosquamous reaction pattern with a significant impact on quality of life. Type I PRP is the most common PRP variant, presenting as erythematous papules emerging in a follicular distribution and later coalescing into plaques with characteristic islands of sparing; histologically, an alternating pattern of orthokeratosis and parakeratosis is considered the hallmark of PRP (checkerboard hyperkeratosis). Other PRP variants (types II-V) differ in their age of onset and clinical presentation. Type VI PRP is a rare PRP subtype associated with human immunodeficiency virus infection and is occasionally associated with diseases of the follicular occlusion tetrad. Caspase recruitment domain family, member 14 (CARD14)-associated papulosquamous eruption and facial discoid dermatitis are newly described disease states that have an important clinical overlap with PRP, creating shared conundrums with respect to diagnosis and treatment. The etiology inciting PRP often remains uncertain; PRP has been suggested to be associated with infection, malignancy, or drug/vaccine administration in some cases, although these are based on case reports and causality has not been established. Type V PRP is often due to inborn CARD14 mutations. Furthermore, recent literature has identified interleukin-23/T-helper-17 cell axis dysregulation to be a major mediator of PRP pathogenesis, paving the way for mechanism-directed therapy. At present, high-dose isotretinoin, ixekizumab, and secukinumab are systemic agents supported by single-arm prospective studies; numerous other agents have also been trialed for PRP, with variable success rates. Here, we discuss updates on clinical manifestations, present new insights into etiopathogenesis, and offer a survey of recently described therapeutic options.