Chronic prurigo (CPG)

Prurigo simplex (acute/subacute), prurigo nodularis (Hyde), papular/nodular/plaque-shaped chronic prurigo, lichen urticatus, strophulus (infantum/adultorum), actinic prurigo, prurigo gestationis.

Chronic recurrent, polyetiological itching condition with imagined (!) seropapules as the first symptom. The itch-scratch action by the patient in a cycle leads to rubbing acanthomas, excoriated acanthomas, as well as papular, nodular, or plaque-like lesions. The IFSI summarizes all prurigo subtypes as phenotypes of chronic prurigo (CPG).

Women are affected about equally frequently as men. Peak age > 60 years. Prevalence is about 5 in 10’000, but is thought to be underestimated. Children often show acute papular urticaria (“strophulus infantum”) with seasonal clustering (summer/autumn). Comorbidities: atopic diathesis, internal and neurological comorbidities.

CPG according to IFSI in phenotypes:

• Papular (e.g., prurigo simplex subacuta, Hebra)
• Nodular (prurigo nodularis, Hyde)
• Other/overlapping patterns: plaque-like, lichenified, excoriated; UV-associated special form actinic prurigo; prurigo gestationis.

Neuroimmune process with Th2 dominance (including IL-4/IL-13) and IL-31 axis, peripheral and central neuronal sensitization, reduced intraepidermal nerve fiber density. TRP ion channels: TRPV1/TRPA1 promote pruritus and neuroinflammation; TRPM8 (menthol) mediates antipruritic cold signals. Triggers/amplifiers: hormonal, GI dysfunction, liver/kidney, infections, atopic/allergic diathesis, nerve root irritation; psychosocial factors maintain the cycle.

Severe punctate pruritus, seropapules, urticarial papules/papulovesicles, rapid excoriation with crusting; in nodular phenotype, rough hyperkeratotic nodules. Symmetrical distribution in easily accessible areas, often traces of scratching; sleep disturbance common. In actinic prurigo: light-exposed areas, cheilitis.

Itch for at least 6 weeks, scratching action by the patient, resulting in pruriginous lesions and the typical morphology mentioned above. 

Medical history regarding triggers (UV, insects, medications, systemic diseases). Scores: PP NRS 0–10 (peak pruritus in the last 24 hours; clinically relevant improvement usually ≥ 4 points), DLQI/ItchyQoL; assess sleep quality. Laboratory (BB, BSR/CRP, liver/kidney, uric acid if necessary) and targeted screening (infections, metabolic/endocrine, malignancy). Biopsy for nodules/atypical course. Photoprovocation for suspected actinic prurigo; scabies diagnosis for corresponding clinical presentation.

Stretch marks on arms/legs, upper back, outer thighs, front of chest; rarely on the face (except for actinic). Interscapular “butterfly zone” often spared.

Punctiform, sometimes burning itching with immediate relief when scratched until bleeding. Chronic recurrent course, worsening at night, sleep disturbance. Seasonal/UV triggers or insect contact possible.

Papular: mild superficial perivascular lymphocytic infiltrate, occasionally eosinophils; ulceration/crusting, dermal fibrosis upon excoriation.

Nodular: marked acanthosis, orthohyperkeratosis (focal parakeratosis), Pautrier neuromas, vertically oriented collagenous fibrosis.

Actinic: acanthosis/spongiosis, perivascular lymphohistiocytic (partly eosinophils).
 

Impetiginization, scarring, post-inflammatory hyper/hypopigmentation, loss of sleep/quality of life; do not miss prebullous pemphigoid; pseudopterygium in actinic prurigo.

Chronic-recurrent; idiopathic cases rarely “curable,” but well controllable with multimodal management. Actinic prurigo often improves during puberty.

Trigger reduction; consistent barrier care; nails cut short twice a week; alternatives to scratching/habit reversal; sleep hygiene. UV protection (including UVA) for actinic prurigo.

1. Pereira MP, et al. International consensus definition and classification of prurigo and its variants. J Eur Acad Dermatol Venereol. 2022.
2. Zeidler C, et al. Chronic prurigo: consensus definition, classification and diagnosis. Acta Derm Venereol. 2018.
3. Ständer S, et al. European guideline on chronic prurigo management. J Eur Acad Dermatol Venereol. 2020.
4. Mollanazar NK, et al. Chronic itch: neuronal and immunologic pathways. J Invest Dermatol. 2016.
5. Ständer S, et al. IL-31 in prurigo nodularis and prurigo simplex. Br J Dermatol. 2021.
6. Ständer S, et al. Neuro-immune interactions in pruritus. Nat Rev Immunol. 2022.
7. Elmariah SB, et al. Nemolizumab for prurigo nodularis: efficacy and safety. N Engl J Med. 2023.
8. Furue M, et al. Capsaicin in pruritus management: mechanisms and practical use. Itch (Phila). 2021.
9. Garcovich S, et al. Chronic prurigo: update on pathogenesis and therapy. Front Med. 2021–2024 (reviews).
10. European/Swiss PN guidance and recent RCTs (2019–2025) summarizing dupilumab, JAK inhibitors, phototherapy.