Pityriasis rubra pilaris is a rare papulosquamous disease characterized by great variability. The clinical spectrum ranges from localized infestation of the extremities to erythrodermic forms. Treatment often proves difficult. Currently, oral retinoids are considered first-line systemic therapy. Biologics are also increasingly being used for refractory courses – in this case as an add-on to acitretin.
DeBiasio et al. describe the case of an otherwise healthy 58-year-old woman who developed an extensive erythematous scaly rash that began on the face and scalp and rapidly spread to the trunk and limbs [1]. The patient had no history of eczema or psoriasis. The histological findings of a biopsy revealed that it was a classic PRP. The treatment proved to be relatively lengthy, but ultimately the combined use of acitretin and ustekinumab proved to be effective.
Initially, half of the body surface was affected
The patient’s rash (Fitzpatrick skin type II) was strikingly symmetrical, consisting of bright red scaly plaques on the face, trunk and limbs with follicular papules in the dorsal area of the hand and around the edges of the spreading plaques [1]. The BSA (body surface area) was 50%. The scalp showed slight, diffuse erythema and scaling. An orange-red, waxy palmoplantar keratoderma and follicular papules manifested in the area of the knuckles. Individual islands were absent on the trunk. Psoriasis and progressive symmetrical erythrokeratoderma were considered as differential diagnoses to classic PRP. A drug reaction was considered unlikely; at that time, the only medication taken regularly was citalopram 20 mg/d. The histologic findings of a punch biopsy confirmed the diagnosis of PRP: there was alternating parakeratosis and orthokeratosis at vertical and horizontal levels, irregular psoriasiform hyperplasia, thickened papillary dermal plates, a preserved granular layer, and a perivascular lymphocytic infiltrate in the superficial dermis.
| Pityriasis rubra pilaris (PRP) usually occurs between the ages of 40 and 60 [4]. The course and clinical symptoms vary greatly from individual to individual. Regardless of the subtype of PRP (I-VI), 90% of patients develop flat, erythematous plaques during the course of the disease, in a fifth of cases with an emphasis on the elbows and knees [5]. Scaling of the skin occurs in around 90% of cases. Palmoplantar keratoderma and diffuse alopecia are seen in around three quarters of PRP patients and a large proportion have nail involvement (pachyonychia, dyschromasia or onycholysis). Around 80% are affected by itching and around half of PRP patients suffer from burning of the skin [5]. |
Multi-track empirical treatment: patience paid off
The patient initially received acitretin 10 mg/d twice daily plus betamethasone valerate ointment 0.1% [1]. One month later, the rash had spread further and the erythroderma increased. In addition, there was nocturnal itching combined with feelings of tension on the skin and chills. The acitretin dose was then increased to 20 mg/d and combined with ustekinumab (45 mg, s.c.) as an add-on. The usual psoriasis regimen was used: after the loading dose, ustekinumab was initially administered at four-week intervals and then every 12 weeks. After the second dose of ustekinumab, there was a gradual improvement and three months later the skin symptoms had almost disappeared. The palmoplantar keratoderma regressed completely. Only the scalp continued to show erythema, scaling, itching and some alopecia. The dose of ustekinumab was then increased to 90 mg, which reduced the symptoms on the scalp. The only side effect was some sticky palms due to the acitretin, which was subsequently reduced to 10 mg/d. The patient was advised to maintain this regimen of low-dose acitretin and ustekinumab 90 mg (every 12 weeks). The laboratory values (complete blood count, liver function, lipids) remained within the normal range. The plan is to slowly phase out the therapy over 1-2 years.
Discussion
There are still many unanswered questions about the aetiopathogenesis of PRP. The therapeutic procedure is largely based on case series, recommendations and individual experience. In adults with PRP who do not respond adequately to topical preparations (emollients, urea, topical steroids), systemic treatment with retinoids such as oral acitretin is considered a first-line therapy [2]. However, treatment-refractory courses are not uncommon [1]. Relatively high doses of acitretin are required for an adequate response and undesirable side effects often limit patient compliance. More recently, it has emerged that PRP shares some molecular, histologic and clinical features with psoriasis [3]. In this context, some of the biologics approved for psoriasis have been used in off-label use with PRP, often resulting in good efficacy and tolerability, as in the example of the present case report [1–3].
Literature:
- DeBiasio C, Cyr J, Ayroud Y, Glassman SJ: A case of classic adult pityriasis rubra pilaris successfully treated with a combination of acitretin and ustekinumab: A case report. SAGE Open Med Case Rep, 2022 Apr 19; 10: 2050313X221093453.
- Roenneberg S, Biedermann T: Pityriasis rubra pilaris: algorithms for diagnosis and treatment. JEADV 2018; 32(6): 889-898.
- Brown F, Badri T: Pityriasis Rubra Pilaris. 2020 Jun 29. StatPearls [Internet]. StatPearls Publishing; 2020.
- “Pityriasis rubra”, https://flexikon.doccheck.com/de/Pityriasis_rubra,(last accessed 13.08.2024).
- Kahlert K, et al: Pityriasis rubra pilaris – a rare inflammatory dermatosis with many facets. Act Dermatol 2019; 45: 32-39.
DERMATOLOGY PRACTICE 2024; 34(4): 28
Cover picture: ©Kelly McGauran, wikimedia
