Pityriasis rubra pilaris (overview) L44.0

Devergie's disease; Devergie's syndrome; IL-12/23 inhibitor; TNF inhibitor;

Devergie, 1863

A rare, predominantly acquired, chronic inflammatory, psoriasiform keratinization disorder of unknown etiology, associated with follicular keratoses and diffuse palmar-plantar hyperkeratoses. Although the skin lesions exhibit a psoriasiform pattern, there is no etiopathogenetic relationship to psoriasis. In rare cases , Grover’s disease-like presentations may occur (Hofmann J et al. 2025). 

According to Griffith, there are 5 distinct types, to which an HIV-associated form is added:

1. Classic adult type (approx. 50%): 80% resolution after 3 years. 
2. Atypical adult type ( approx. 5%): Predominantly chronic course; palmar-plantar hyperkeratosis; remissions within a 3-year period occur in only 20% of cases. 
3. Classic juvenile type (approx. 10%): Corresponds to the Type 1 variant. First manifestation as early as the 1st or 2nd year of life. Resolution usually within 1 year. Chronic course is rare. 
4. Delimited juvenile type (approx. 25%): Psoriasis-like appearance; varying rates of resolution (1/3 within 3 years). Often associated with infection. 
5. Atypical juvenile type (approx. 5%): chronic course, follicular form, progression to extensive plaques with ichthyosis-like scaling; occasionally familial (GOF mutations inthe CARD14 gene can be detected—see below: CARD14-associated papulosquamous eruption—Craiglow BG et al. 2018)
6. HIV-associated form (< 5%). Erythrodermic courses have been reported (see Kahlert R et al. 2019) 

Incidence: 0.2 per 100,000 per year; prevalence: 1 per 400,000 inhabitants. 

Note: The low prevalence accounts for the limited data available on pathogenesis, clinical presentation, and treatment, and in particular on the long-term course of the disease (Griffiths WA 1980). 

• Unknown (except for Type 5).    
• Essentially, this is a hyperproliferative keratinization disorder with increased turnover rates.
• With the exception of Type 5, it usually occurs sporadically.
• Type 5 (hereditary, atypical juvenile type) is inherited in an autosomal recessive manner. In isolated cases, autosomal dominant inheritance has been demonstrated. In the latter cases, a heterozygousgain-of-function (GOF)mutation in the CARD14 gene was identified (Lwin et al. 2018). 
• Hormonal disorders are under discussion.
• A deficiency in retinol-binding protein and disturbances in vitamin A metabolism have been described. 
• There is discussion of excessive activation of inflammatory signaling pathways and, consequently, elevated concentrations of inflammatory cytokines (TNF-alpha,IL-23) in affected skin. The successful treatment with biologics (adalimumab, ustekinumab) also supports this type of signaling in this pathophysiological process (Kahlert K et al. 2019). 
• Viral Inducers: In pityriasis rubra pilaris, the onset of the disease has been observed following infections withEBV, CMV, VZV, hepatitis C (Cecchi R et al. 1994), and HIV. In the case of HIV infection, the onset of PRP may represent the initial manifestation of an IIV infection.
• Tumors: Case reports of PRP occurring in the context of tumors (hepatocellular carcinoma, bronchial carcinoma) are known, as is an association with medications (insulin) — (Kahlert K et al. 2019). 

Basically possible in any age group (see also classification into juvenile and adult types); in the juvenile type, clusters are found in the first decade of life (approx. 12% of cases), in the adult type in the 6th-7th decade of life (approx. 60% of cases).

The disease is characterized by the following main symptoms:

1. chronic, changeable, also seasonal course lasting for years
2. extensive, red-orange-colored, psoriasiform or ichthyosiform scaling plaques with sharply marked recesses(nappes claires)
3. extensive palmo-plantar keratoses (78% of cases)
4. follicular keratoses
5. Diffuse alopecia (76% of cases)
6. Nail involvement (paronychia, dyschromasia, onycholysis - 72% of cases)
7. Pruritus (80% of patients)
8. Histology: diffuse superficial dermatitis, horizontal and vertical parakeratosis with follicular hyperkeratosis

Initial symptoms: Dense, follicular, keratotic, red to red-brownish (orange-red), pinhead-sized, pointed papules with central, conical or crater-shaped sloping keratosis, which aggregate to form large plaques, especially on the back of the fingers and hands and the extensor sides of the extremities.

Pityriasis rubra pilaris type 1 (classic form): Extensive pityriasiform reed-like, often marginal, sharply defined, follicular ("nutmeg rubbing"), lichenified erythema or plaques on the capillitium, face (especially eyebrows, nasolabial folds), also on the trunk.

Pityriasis rubra pilaris type 2 and 3: Types 2 and 3 are morphologically not different from the classic adult type.

Pityriasis rubra pilaris type 4 (circumscribed juvenile - psoriasiform - type): Sharply defined plaques on the knee and elbow as well as follicular hyperkeratosis with perifollicular erythema.

Pityriasis rubra pilaris type 5 (atypical juvenile form): This form is characterized by early onset (usually already in the 1st year of life - see below). CARD14-associated papulosquamous eruption - Craiglow BG et al. 2018 ) and long disease duration. Sclerodermatous changes of the hands and feet are particularly emphasized.

Orthohyperkeratosis alternating with parakeratosis in a vertical and horizontal direction (checkerboard pattern) is characteristic. Follicular keratoses. Bulky superficial perivascularly oriented lymphocytic infiltrate (no Munro microabscesses).

The most important (and most frequent misdiagnosis) is psoriasis.

Contact dermatitis (years of chronicity with spontaneous progression would be unusual for contact dermatitis, localization of HV, palmoplantar keratoderma)

Drug reactions (high acuteity, sudden onset with relationship to medication)

Atopic dermatitis (IgE-associated laboratory symptoms, flexural eczema, signs of atopy)

Mycosis fungoides: (rather surface-smooth plaques, histology is diagnostic, it is more difficult to differentiate an erythrodermic MF from an ertythrodermic adult type of PRP with nappes claires. Histology is also diagnostic in this case).

Especially in adults the disease can take an acute course. Complicated is the development of erythroderma.

Development of an ectropion, especially in erythrodermatic pityriasis rubra pilaris.

Summary of Therapeutic Evaluation

• Standard first-line therapy: Acitretin or isotretinoin for extensive PRP.
• Alternative conventional systemic therapy: methotrexate; in specific cases, cyclosporine.
• For treatment-refractory cases: biologics, particularly antibodies targeting IL-17 and IL-23.
• New therapeutic approaches: JAK inhibitors such as upadacitinib, abrocitinib, and tofacitinib; to date, primarily case reports.
• Local therapy (adjuvant): Emollients and keratolytic agents. The evidence is generally low to moderate and low for most procedures. A major problem in the assessment is the possibility of spontaneous remission, particularly in classic adult PRP (Type I). High response rates from small case series should therefore not be equated with proven superiority.
• Note: The targeted therapies mentioned are generally off-label uses for PRP.

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