Pityriasis rubra pilaris (Prp)

Synonyms

Lichen accuminatus; M.Divergie.

Epidemiology

Rare papulo-squamous disease. 1: 5000 of dermatologic cases in UK. Any ethnic group. F=M.

Definition

Chronic inflammatory papulo-squamous skin disease with a spectrum of several clinical phenotypes.

Aetiology & Pathogenesis

No clear genetic background. In familial cases, mutations in the caspase recruitment domain family. It is occasionally precipitated and aggravated or even maintained by infections or drugs such as sorafenib, insulin, imatinib, telaprevir, and vaccinations.

Signs & Symptoms

Psoriasiform reddish-orange tiny pinpoint elevated and follicular bound scaling, forming small and large sharply demarcated patches, sometimes burning and evolving into erythroderma; uninvolved skin inbetween (nappes claires). Involvement of palms and soles, mimicking psoriasis, chronic eczema or keratoderma.

Localisation

Localized on trunk, elbows, knees, palms and soles or total body (erythroderma).

Classification

The recent last classifications identifies six main forms of pityriasis rubra pilaris:

Type 1: classical adult-onset

Type 2: atypical adult-onset

Type 3: classical juvenile-onset

Type 4: circumscribed juvenile

Type 5: atypical juvenile-onset

Type 6: HIV - associated

Laboratory & other workups

No specific tests; biopsy.

Dermatopathology

Plump acanthosis and papillomatosis with broad rete ridges, horizontally and vertically alternating ortho- and hyperparakeratosis (checkerboard sign); follicular hyperkeratotic plugs. No or rather sparse lymphocytic infiltrate.

Course

Disease duration in most of the patients <1year.

Complications

None except erythrodermic courses and type 1 associated underlying malignancy disorder.

Diagnosis

Clinical features and histopathology.

Differential diagnosis

Psoriasis, secondary syphilis, pityriasis rosea, parapsoriasis, nummular eczema, hypertrophic lichen planus, chronic palmo-plantar eczema, keratosis follicularis, Darier disease.

Prevention & Therapy

Only avoiding aggravating factors

Topical therapy depending on lesion type and amount of body surface area.
- Topical corticosteroids, especially mid to higher potency.
- Vitamin D3 and its analogues (calcipotriol, tacalcitol).
- Vitamin-A acid derivatives (tazarotene gel).
- UV light therapy regimen such as bath-photo therapy 15% NaCl + UVB. Phototherapy (UVA +) UVB/narrow band UVB 311 nm. Photochemotherapy: 8-(5-) MOP + UVA (PUVA).

Systemic treatment in widespread Prp: methotrexate, azathioprine, retinoids (acitretin, isotretinoin, alitretinoin), ciclosporin, fumarates, biologics (TNFalpha, ustekinumab, secukinumab).

1.5.3 Pityriasis rubra pilaris (Prp)