Pityriasis rubra pilaris
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Synopsis
Pityriasis rubra pilaris (PRP) is characterized by an acute cutaneous eruption that is usually accompanied by pruritus and pain. There are both acquired and heritable forms. Classic cutaneous lesions include follicular keratotic papules on an erythematous base coalescing to form large, orange-red plaques with characteristic islands of sparing. PRP commonly begins on the scalp and rapidly spreads in a craniocaudal direction, and it has the potential to quickly progress to erythroderma over several weeks' time. Additional features include an orange-red or bright yellow palmoplantar keratoderma. PRP can be classified into 6 clinical types. The clinical types have been suggested to predict response to therapy and disease course, but this has not been validated.
- Type I (classic adult type, 55% of cases) – Occurs in adults. It is the most common subtype and may clear without therapy within 3-5 years. Relapses are uncommon.
- Type II (atypical adult type, 5% of cases) – A rare subtype seen in adults. It is characterized by more ichthyosiform (plate-like) scale, increased hair loss, and a chronic and severe course.
- Type III (classic juvenile type, 10% of cases) – Occurs in children and adolescents. It resembles type I PRP clinically, although erythroderma is less common. Many cases resolve in less than 3 years, but some cases persist longer.
- Type IV (circumscribed juvenile type, 25% of cases) – Most common subtype in children and adolescents. It is characterized by focal lesions on the extensor surfaces of extremities, over the Achilles, and palmoplantar keratoderma. The clinical course is variable.
- Type V (atypical juvenile type, 5% of cases) – Typically occurs in the first 2 years of life. It is the most common familial form of PRP and may be associated with CARD14 gene variations, although of note, individuals with CARD14 gene variations (also termed CARD14-associated papulosquamous eruption), may present with features of atypical PRP, classical PRP, or psoriasis.
- Type VI (HIV-associated type, < 1% of cases) – Occurs in HIV-infected individuals. It may resemble type I PRP or may be part of a follicular occlusion tetrad that includes acne conglobata, hidradenitis suppurativa, and lichen spinulosus.
The etiology of PRP has not been clearly defined. The onset of disease has been associated with vaccines, infection, malignancy, ultraviolet (UV) exposure, and minor skin trauma. Medications have been implicated as causative in a small number of patients, but more studies are needed. Potential culprits include tyrosine kinase inhibitors (ponatinib, imatinib, sorafenib), topical Toll-like receptor 7 (TLR7) agonists (imiquimod), phosphoinositide 3-kinase inhibitors (ofatumumab and idelalisib), antiviral medications (telaprevir, sofosbuvir), and less commonly, programmed cell death protein 1 (PD-1) inhibitors (pembrolizumab), vascular endothelial growth factor (VEGF) inhibitors (bevacizumab), statins (simvastatin), insulin, and angiotensin-converting enzyme (ACE) inhibitors (ramipril). While infliximab can be an effective treatment for PRP, there is one case report of infliximab-induced PRP.
While there are reports of heritable forms, the large majority of PRP cases are acquired and without sex predilection. The incidence of the acquired form occurs in 2 slight peaks: during the first and second decades and during the sixth decade, although it may present at any age.
Codes
ICD10CM:L44.0 – Pityriasis rubra pilaris
SNOMEDCT:
3755001 – Pityriasis rubra pilaris
Look For
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- Psoriasis – See Diagnostic Pearls.
- Seborrheic dermatitis – Appears similar to early-stage PRP with erythema and scale of the scalp and forehead.
- Mycosis fungoides / Sézary syndrome – Sometimes very similar to PRP, and occasionally demonstrates islands of sparing. Look for lymphadenopathy, circulating malignant lymphocytes as determined by flow cytometry, leonine facies, and characteristic histopathologic findings.
- Wong-type dermatomyositis – Features of both dermatomyositis, such as atrophic dermal papules of dermatomyositis (ADPDM, formerly called Gottron papules), Gottron sign and heliotrope rash, and PRP. May be accompanied by myositis or amyopathic dermatitis.
- Drug-induced erythroderma – May have less scale and lack palmoplantar keratoderma. Any medications started within 3 months of rash onset should be considered.
- Atopic dermatitis – Ask about a history of atopy. Look for lichenified plaques on the flexural surfaces and neck and excoriations.
- Caspase recruitment domain family member 14 gene (CARD14)-associated papulosquamous eruption refers to a distinctive phenotype with overlapping features of psoriasis and PRP. The patients typically present in the first 2 years of life and report a family history of psoriasis or PRP. The cheeks, chin, and ears are typically affected. This disease is difficult to treat using conventional therapies, while treatment with ustekinumab appears to be effective.
- Acrokeratosis paraneoplastica (Bazex syndrome) – Thick, scaly plaques present on the ears and face in addition to palmoplantar keratoderma.
Best Tests
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Management Pearls
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Therapy
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Drug Reaction Data
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.Subscription Required
References
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Last Reviewed:01/01/2023
Last Updated:01/04/2023
Last Updated:01/04/2023
Pityriasis rubra pilaris