The Incidence of Acantholysis in Pityriasis Rubra Pilaris—Histopathological Study Using Multiple-Step Sections and Clinicopathologic Correlations

Facial Discoid Dermatosis. A 13-Case Series

Facial discoid dermatosis (FDD) is a condition characterized by papules-plaques primarily affecting the face. FDD has been associated with psoriasis, seborrheic dermatitis, and pityriasis rubra pilaris. We conducted a retrospective multicenter study with 13 patients diagnosed with FDD in Spain (2014-2022). Patient demographics, clinical presentations, histopathological findings, and treatment outcomes were collected. FDD shows as erythematous-orange, nummular papules and/or plaques with dry scales that primarily affect the facial region. Histopathological analysis revealed a consistent pattern of psoriasiform hyperplasia with confluent parakeratosis, without neutrophils within the epidermal layers. This study provides essential insights into the clinical and histopathological features of FDD within a predominantly Caucasian patient cohort. The presence of distinct clinical features and consistent histological findings underscores the uniqueness of FDD. However, the variability in histological features and persistence of lesions despite various treatments highlight the need for further research to better understand the pathogenesis of FDD and develop effective therapies.

A Review on Pityriasis Rubra Pilaris

Pityriasis rubra pilaris (PRP) is an idiopathic, papulosquamous inflammatory dermatosis. It is characterized by hyperkeratotic follicular papules coalescing into orange-red scaly plaques, islands of sparing, and palmoplantar keratoderma. PRP can be subdivided into six clinical subtypes according to Griffiths' classification, based on age of onset, disease extent, prognosis, and other associated features. The sixth subtype of PRP occurs in individuals affected by HIV infection, and retroviral screening in all de novo cases of PRP is advised. Other reported associations include various infections, autoimmunity, drugs, and malignancies, although the true significance of these is still unclear. The genetic basis for familial cases, most commonly categorized under the fifth subtype, has been mapped to gain of function mutations in the caspase recruitment domain family, member 14 (CARD14) gene. Treatment of PRP remains a challenge to this day due to a paucity of high-quality evidence. Therapeutic regimens have been guided mostly by case reports and case series, with the mainstay of treatment being oral retinoids. Recently, biologics have emerged as a promising treatment for PRP. We present a review of the clinicopathologic features, pathogenesis, associated disorders, and treatment of PRP, with an emphasis and critical appraisal of the existing literature on the latter.

'Hints' in the horn: diagnostic clues in the stratum corneum

The stratum corneum or horny layer is the uppermost layer of the epidermis, and is mainly responsible for the skin's barrier function. In spite of its complexity at the ultrastructural and molecular level, the features accessible to visualization on conventional histology are relatively limited. Nevertheless, knowledge of subtle clues that one may observe in the stratum corneum can prove useful in a wide range of situations in dermatopathology. We herein review a selection of common and rare entities in which the horny layer may reveal significantly important hints for the diagnosis. These clues include parakeratosis and its different patterns (focal, confluent, alternating, associated with spongiosis, epidermal hyperplasia or lichenoid changes), subcorneal acantholysis, infectious organisms in the stratum corneum (including fungal, bacterial and parasitic), thickening or thinning of the stratum corneum and the presence of different kinds of pigment. Even when normal, the horny layer may prove to be useful when seen in association with severe epidermal damage, a combination of features testifying to the acute nature of the underlying pathological process.

Follicular Psoriasis: Differentiation from Pityriasis Rubra Pilaris-An Illustrative Case and Review of the Literature

The follicular presentation of psoriasis is a well-described but uncommon variant. In some cases, follicular psoriasis may clinically and histopathologically mimic pityriasis rubra pilaris. There are several reports discussing the resemblance of widespread follicular psoriasis in children to pityriasis rubra pilaris. We describe a case of follicular psoriasis in a 16-year-old black girl with acrally distributed follicular hyperkeratotic papules with associated keratoderma of her plantar surfaces resembling pityriasis rubra pilaris.