1.5.3 Pityriasis rubra pilaris (Prp)
Grading & Level of Importance: C
Lichen accuminatus; M.Divergie.
Rare papulo-squamous disease. 1: 5000 of dermatologic cases in UK. Any ethnic group. F=M.
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.
Localized on trunk, elbows, knees, palms and soles or total body (erythroderma).
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.
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.
Disease duration in most of the patients <1year.
None except erythrodermic courses and type 1 associated underlying malignancy disorder.
Clinical features and histopathology.
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).
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